Chapter 132. Myocarditis, Pericardial Disease, and Cardiac Tamponade

1. What are the most common etiologies of pericarditis and myocarditis?

2. How are pericarditis and myocarditis diagnosed?

3. Which imaging modality is most accurate in diagnosing myocarditis?

4. What are the evidence-based physical examination, radiographic, electrocardiographic, and imaging findings used in the diagnosis of cardiac tamponade, and how is it managed?

5. What are the differences in physical examination, testing results, and treatment of constrictive pericarditis versus cardiac tamponade?

Introduction

Acute myocarditis is an inflammatory infiltration of the myocardium. The clinical sequelae of this disease include subclinical disease to fulminant cardiogenic shock.

Acute myocarditis can present a challenging diagnostic dilemma. Traditionally, the diagnosis of myocarditis is made by endomyocardial biopsy. In acute myocarditis, biopsy shows areas of necrosis with a lymphocytic infiltration. However, endomyocardial biopsy is subject to procedural risks, sampling bias, and poor sensitivity. Noninvasive cardiac magnetic resonance imaging (MRI) has become an alternative mechanism for diagnosing myocarditis.

Pathophysiology

The most common cause of myocarditis is a viral pathogen. However, other infectious, autoimmune, and toxic causes occur as well. Initial studies in the latter half of the 20th century indicated Coxsackie B virus as the frequent causative agent in endomyocardial biopsies. However, since the 1990s adenovirus has emerged as the more frequent viral agent. Since that time, parvovirus and other viruses have been seen in the biopsy results of patients with myocarditis. Other viral causes of acute myocarditis have been reported in patients with hepatitis C virus (HCV), Epstein-Barr virus, and cytomegalovirus (CMV).

Infectious etiologies other than viruses have been implicated as a cause of myocarditis, including mycoplasma and Borrelia burgdorferi (Lyme disease). In developing countries, Trypanosoma cruzi has been known to infect the myocardium causing Chagas disease.

Presentation

The clinical presentation of patients with myocarditis can range from mild dyspnea and chest discomfort to fulminant cardiogenic shock. Patients may report a viral prodrome in the weeks preceding presentation, including fevers, respiratory, or GI symptoms. According to the European Study of Epidemiology and Treatment of Inflammatory Heart Disease, patients with myocarditis present with dyspnea (72%), chest pain (32%), and arrhythmias (18%). Patients may also present with symptoms related to congestive heart failure, including fatigue, orthopnea, paroxysmal nocturnal dyspnea, palpitations, and syncope.

As an infiltrative process, the amount of affected myocardium can be highly variable in myocarditis. Some patients may present with ventricular arrhythmias if the conducting system is involved while other patients may present with a dilated cardiomyopathy.

The physical examination of patients with acute myocarditis may correlate with the patients' symptoms. In patients with mild symptoms, the physical examination may be relatively normal. However, patients with severe myocarditis may appear in cardiogenic shock. Diaphoresis, rales, jugular venous distention, hypotension, and peripheral edema can all be seen in patients with myocarditis.

Diagnosis

The electrocardiogram (ECG) in myocarditis may show sinus tachycardia and nonspecific ST-segment changes and T-wave inversion. ST-segment elevation and Q-waves that suggest acute myocardial ischemia can occur in myocarditis. Patients may also present with bundle-branch blocks, atrioventricular block, or ventricular tachyarrhythmias. An associated pericarditis may be present in patients with myocarditis, so called myopericarditis, which can also cause diffuse ST-segment elevation in addition to PR-segment depression.

Patients with myocarditis can have elevated biomarkers, such as troponin-I, CK-MB, and CPK. Troponin-I levels are more commonly elevated than other cardiac biomarkers. However, troponin-I elevation has a low sensitivity (34%) for myocarditis.

The white blood cell count may range from completely normal to a mild leukocytosis in patients with myocarditis. Viral myocarditis may cause a nonspecific lymphocytic predominance. Eosinophilia may be associated with drug-induced myocarditis or an infiltrative disease like Churg-Strauss. Thrombocytopenia may be present due to the acute viral illness, or from splenic sequestration due to splenomegaly, which may accompany congestive heart failure.

The serum chemistry in patients with suspected myocarditis varies according to the disease burden of the myocardium. Severely affected individuals may have chemistries that correlate with congestive heart failure, including hyponatremia due to sodium dysregulation and reduced kidney function due to poor cardiac output. Elevated liver transaminases (AST and ALT) along with markers of synthetic function (PT/INR, PTT) may be elevated due to hepatic congestion.

Chest radiography may reveal pulmonary vascular congestion and cardiomegaly due to a dilated cardiomyopathy or pneumonia if the myocarditis is caused by mycoplasma.

The role of echocardiography in the diagnosis of myocarditis is nonspecific. Even in severe cases of myocarditis, echocardiography may only identify a dilated cardiomyopathy or, less commonly, hypertrophic or restrictive cardiomyopathies. Regional wall motion abnormalities may mimic changes commonly seen with ischemia.

Although echocardiography has been the traditional imaging modality of choice, it can be normal in less severe cases of myocarditis. Therefore, computed tomography or magnetic resonance imaging may be considered in the diagnosis of myocarditis when echocardiography is nondiagnostic. MRI identifies myocarditis in 30% of patients with chest pain, elevated troponins, and normal coronary arteries. In cases where edema, capillary leak and necrosis can be assessed, cardiac MRI has a sensitivity of 67%, a specificity of 91%, and a diagnostic accuracy of 78%.

Endomyocardial biopsy is the gold standard for diagnosing myocarditis. However, the biopsy procedure has obvious risks, can vary by interpreter, lacks prognostic value, and has a low sensitivity due to sampling error. For these reasons, endomyocardial biopsy should be reserved for cases when other infiltrative disorders are in the differential diagnosis, such as cardiac sarcoidosis or giant cell myocarditis. Histologically, an inflammatory cellular infiltrate may be seen with or without myocyte necrosis.

Management

The low incidence of myocarditis precludes performing randomized controlled trials with sufficient power to assess therapeutic regimens. The basis of therapy for patients with myocarditis remains largely supportive. The majority of patients with myocarditis will recover fully. For the patients with a stable clinical course, the basis of therapy resides in angiotensin-converting enzme (ACE) inhibitors, beta-blockers, and diuretic therapy. Patients with severe left ventricular (LV) dysfunction can rapidly progress to cardiogenic shock. These patients may require a left ventricular assist device (LVAD) or extracorporeal membrane oxygenation (ECMO) as a bridge to cardiac transplantation.

Patients with myocarditis may have an increased risk of arrhythmias, requiring temporary pacemakers for bradycardia or complete heart block, or antiarrhythmic agents such as amiodarone for ventricular tachyarrhythmias. For patients who present with or have ventricular arrhythmias after the diagnosis of myocarditis, implantable cardiac defibrillators (ICD) may be considered once the acute phase of the illness has resolved. In addition to patients with ventricular tachycardia or fibrillation, those patients with an ejection fraction less than 35% following resolution of the acute phase of myocarditis, should be considered for ICD implantation. It should be noted that patients under consideration for ICD placement should have a life expectancy longer than one year on optimal medical therapy.

While myocarditis is a lymphocytic infiltrative disease, immunosuppressive agents show only marginal beneficial effects. One small trial suggests that patients with human leukocyte antigen expression on biopsy have modest benefit (ejection fraction improvement and New York Heart Association [NYHA] class) from prednisone and azathioprine.

Introduction

Acute pericarditis is defined as signs and/or symptoms consistent with pericardial inflammation of less than three weeks' duration. The true incidence of pericarditis is difficult to quantify since many cases go undiagnosed. Pericarditis may account for up to 1% of cases of ST elevations on ECG, and account for 5% of emergency room visits. Eighty percent to 90% of cases of pericarditis are idiopathic.

Pathophysiology

Pericarditis can be an acute, subacute, or chronic process. The etiology of acute pericarditis is often idiopathic or viral, though the pericardium can be affected by numerous other disease processes including infectious, neoplastic, autoimmune, and traumatic causes (Table 132-1).

Although the pericardium is not required to maintain life, it serves many functions within the thorax. The pericardium is composed of two layers. An inner layer, the visceral pericardium, adheres to the epicardial surface of the heart and consists of a layer of mesothelial cells. The outer layer is an avascular, fibrous parietal layer and consists of elastin fibers embedded within compact layers of collagen. The visceral pericardium reflects back near the great vessels and forms the inner layer of the parietal pericardium. The pericardial space is formed from these two layers and normally contains up to 50 mL of an ultrafiltrate of plasma. In the pericardium, villi and cilia enhance the resorption of fluid. The capacity of the pericardium to accept increased fluid volume depends on the rate of accumulation. A rapid addition of 50 to 200 mL will dramatically increase pressure and affect cardiac function, whereas a very slow accumulation of large amounts of fluid as in myxedema will have little effect on pressure or hemodynamics.

The collagen matrix of the parietal pericardium gives the pericardium its unique mechanical properties. Functionally, the pericardium facilitates contraction and relaxation of the ventricles and atria, allowing pressure changes on one side of the heart to be transmitted to the other side. Additionally, the pericardium's mechanical properties may determine cardiac output during exercise via the pericardium's direct limitation of the cardiac filling volumes.

Presentation

Acute pericarditis presents with chest pain of abrupt onset as the most common complaint. The pain can be quite severe, sharp in character, and nearly always pleuritic in nature. The sharp pain of acute pericarditis differs from the pressure-like discomfort of myocardial ischemia. The pain may be located substernally or located in the anterior chest, and radiation to the neck, arms and shoulders can also occur (Figure 132-1).

The phrenic nerve, which innervates the trapezius muscles, traverses the pericardium; therefore, radiation to the either trapezius ridge of the left shoulder is very specific for pericardial pain. Classically, the pain associated with pericarditis will improve with sitting up and leaning forward and is exacerbated by lying flat or with slight changes in position. Associated symptoms include dyspnea from splinting due to pain, cough, myalgia, arthralgias, and occasionally hiccoughs.

Vital signs in patients with pericarditis may be normal or show low-grade fever and tachycardia. High fever may indicate a bacterial cause, and these patients should undergo echocardiographic evaluation. There may be associated tachypnea from the dyspnea or pain. The most specific, and pathognomonic, finding associated with pericarditis is the pericardial friction rub. This scratchy, superficial sound likely results from inflamed visceral and parietal pericardium rubbing against each other. Classically, there are three components correlating with ventricular systole, ventricular diastole, and atrial systole. All components, two components, one component, or none may be present, as the finding is not sensitive. Two components would be expected in atrial fibrillation due to loss of the atrial component; rapid heart rates may only produce two components due to summation of the early diastolic rub and presystolic rub. The rub may be composed solely of the ventricular component, which is the last to leave over the course of illness. These rubs, described as triphasic, biphasic, or monophasic, may be confused with other cardiac abnormalities, especially in patients with a monophasic rub, which may be mistaken for a murmur.

The pericardial friction rub is best heard at the left sternal border, often in a well-localized spot but may be heard only at the apex. Therefore, the examiner needs to take a systematic approach to auscultation; position the patient forward or even on his hands and knees with the chest down or lying on his abdomen propped up on his elbows; use the diaphragm of the stethoscope against the chest wall with forced expiration; and listen over the entire left precordium. Frequent examinations may be required to hear the friction rub given its fleeting nature. The sound has been described as the sound produced when walking through snow, or pulling apart two pieces of Velcro. The rub of pericarditis may sound very similar to the harsh sound of Hamman crunch (heard in some patients with pneumomediastinum); care should be taken to differentiate these two auscultatory findings. In uncomplicated pericarditis, the jugular venous waveforms remain unchanged.

Diagnosis

The initial approach to the patient with suspected pericarditis is based on a thorough history, physical examination and testing—ECG, cardiac enzymes, basic chemistry, complete blood count, erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP), and chest radiograph. ECG demonstrates valuable findings for the diagnosis of acute pericarditis (Figure 132-2). Abnormalities are found in approximately 90% of the cases. The most sensitive ECG change of acute pericarditis is ST-segment elevation due to abnormal repolarization secondary to pericardial inflammation. Classically, the ECG of acute pericarditis shows ST elevation in the hexaxial and precordial leads with the exception of AVR and V1 which may have ST-segment depression. The ST elevations have concave shape and are not accompanied by reciprocal changes. In ischemia, on the other hand, the slope of ST elevation is more often convex in shape and accompanied by reciprocal changes on the ECG. These two differences help to distinguish the ST elevation of pericarditis from that of ischemia. In addition, ST-segment elevation, which typically occurs during the first few days of pericardial inflammation, may last up to two weeks. T-wave inversion does not occur at the time of ST-segment elevation nor are there associated Q-waves. PR depression is very specific of acute pericarditis and is attributed to subepicardial atrial injury. In fact, PR depression found in all leads except AVR and V1, which may show PR elevation. This finding may be very useful when the patient has no friction rub and equivocal ST elevation. Electrical alternans, the presence of alternating QRS amplitudes may suggest the presence of a significant pericardial effusion. Serial ECGs at presentation are especially useful because of how the changes evolve in contrast to acute myocardial ischemia or J-point elevation.

Creatinine kinase MB fraction and/or troponin I values may be elevated in 8% to 22% of patients presenting with acute pericarditis. Evidence of elevated troponin or CK-MB laboratory values correlate with ST elevation on the electrocardiogram. The elevation of cardiac enzymes may represent silent myocarditis in addition to pericarditis, or the epicardial inflammation that can accompany acute pericarditis. Acute pericarditis may accompany endocardial ischemia, such that coronary disease may need to be ruled out in patients presenting with pericarditis who have concomitant significant elevations in cardiac biomarkers.

Acute pericarditis may be associated with mild elevations in the total white blood cell count, usually with a lymphocytic predominance. The differential of the white blood cell count may reflect the underlying etiology; viral or idiopathic pericarditis may present with a lymphocytic predominance, whereas bacterial pericarditis may have a neutrophilic predominance.

The erythrocyte sedimentation rate may have mild elevation, but significant elevations in the ESR may suggest an autoimmune etiology, uremia, bacterial processes, or tuberculosis. Patients presenting with uremia may have a pericardial friction rub on exam.

The chest radiograph may be completely normal in viral or idiopathic acute pericarditis. Pericardial effusion should be suspected in the setting of an abnormal cardiac silhouette. An accumulation of more than 200 mL of pericardial effusion will enlarge the cardiac silhouette, indistinguishable from other causes of cardiomegaly. As more fluid accumulates, however, a “water bottle” configuration may develop. In the absence of pulmonary venous congestion, considerable cardiomegaly may be a clue that a pericardial effusion is present. Fluid between the two pericardial layers may show separation of the epicardial fat pad from the outer border of the cardiac silhouette. An abnormal chest radiograph may suggest the etiology for the pericarditis, or a different diagnosis. An infiltrate on chest X-ray may suggest bacterial pericarditis as the etiology. An upper lobe infiltrate, or a completely normal chest X-ray may accompany tuberculosis pericarditis. Pulmonary congestion may suggest ischemia or myocarditis.

Echocardiography is the imaging modality of choice in acute pericarditis because of its availability, lack of radiation exposure, and ability to rule out potentially fatal complications such as tamponade. An echocardiogram is recommended for most patients with pericarditis, especially patients with fever, currently on anticoagulation therapy, in an immunocompromised state, a recent history of trauma, or if there is suspected myocardial involvement. Echocardiography in patients with uncomplicated acute pericarditis may be completely normal. A small effusion may be present which does not necessitate intervention. Large pericardial effusions are uncommon in acute pericarditis and should trigger the clinician to pursue other diagnoses. Focal wall motion abnormalities may suggest that myocarditis may be present.

CT and MRI are emerging as valuable methods for detecting complicated pericarditis. The inflamed pericardium in both acute and chronic pericarditis can be visualized by MRI. The ability to assess fluid attenuation on both CT and MRI allows a noninvasive assessment of the etiology. The thickened pericardial layers and any pericardial effusion can be effectively visualized on cardiac MRI. Furthermore, MRI may be the noninvasive imaging modality of choice for the diagnosis of myocarditis, which can accompany pericarditis.

Management

Patients with a history, physical examination, and testing consistent with pericarditis should receive nonsteroidal anti-inflammatory drugs (NSAIDs) as the initial treatment. Aspirin is preferred over NSAIDs if acute myocardial infarction is the cause of acute pericarditis, as NSAIDs may promote ventricular rupture. Therapeutic options include: aspirin (2–4 g daily), ibuprofen (1600–3200 mg daily), or other NSAIDs at high therapeutic dosing for 2 to 4 weeks' duration. If there is no large effusion and cardiac enzymes are normal, the patient can be discharged and followed up within two to four weeks to ensure resolution. If the pain has resolved, therapy can be discontinued at that time.

Patients that do not have an adequate response to NSAIDs may require narcotic analgesics for pain control. Colchicine in combination with aspirin is an alternative regimen in the treatment of acute pericarditis, and reduces recurrences of pericarditis in comparison to aspirin alone. Colchicine alone is an alternative agent when aspirin or an NSAID is contraindicated. Colchicine should be initiated at a 2 mg loading dose, then 1 mg daily for 2 weeks, but may require maintenance therapy for up to 3 months.

Alternately, a prednisone taper over the course of a week, starting at 60 mg orally can be used. However, patients receiving steroid therapy for acute pericarditis have a higher relapse rate than with other medications. Corticosteroids are indicated in acute pericarditis due to systemic inflammatory diseases or uremia. Corticosteroids also should be considered in patients who are refractory to or have contraindications to aspirin, NSAIDs, and colchicine. However, corticosteroids may promote the development of recurrent pericarditis and should not be used in patients with acute pericarditis due to bacterial infection or tuberculosis. They should also be avoided in patients with postinfarction pericarditis due to the risk of ventricular aneurysm formation.

The most common complication of acute pericarditis is recurrent pericarditis, occurring in 15% to 30% of patients presenting with acute pericarditis. Colchicine is the treatment of choice for recurrent acute pericarditis and can prevent recurrences. In patients with a first episode of pericarditis, patients treated with colchicine therapy (1.0–2.0 mg/d for the first day, then 0.5–1.0 mg/d for 6 months) decreases recurrence (24% vs 51%) over standard therapy plus aspirin.

Introduction

Many inflammatory and noninflammatory conditions lead to excess fluid in the pericardial space, thereby, overwhelming the villi and cilia that physiologically reabsorb fluid and optimize the movement of the pericardial layers over one another (Table 132-1). Often, pericardial effusions accompany episodes of pericarditis and share the same etiology. Sometimes, pericardial effusions are incidentally noted during imaging for other indications. Therefore, clinicians need to quickly determine if a pericardial effusion is a factor in the patient's clinical syndrome, identify any hemodynamic consequences of the effusion, and then appropriately manage with the help of consultants.

Pathophysiology

Effusion formation is most often part of an inflammatory process involving the pericardium. Less commonly, accumulation of lymphatic drainage or blood can occur. The latter is termed hemopericardium and is most commonly associated with ascending aortic dissection, perforation of the atrial or ventricular walls, or direct injury to the pericardium itself. Patients with anasarca, uremia, or myxedema may also develop a significant pericardial effusion. Cardiac tamponade can develop irrespective of the pathophysiology responsible for the development of the effusion. Whether cardiac tamponade is present depends upon many factors, most importantly is the acuity with which the effusion has accumulated. The pericardium is a compliant collagen-based structure with the intrinsic ability to stretch and accommodate a large amount of fluid without causing hemodynamic consequences when effusions accumulate subacutely or chronically. The hemodynamic consequences of a pericardial effusion are determined by the amount of increased pressure within the pericardial sac and the heart's ability to compensate or accommodate this increased pressure. Rapid accumulation of pericardial fluid can lead to very high intrapericardial pressures within a very short amount of time causing hemodynamic collapse despite a small volume effusion. However, even large chronic effusions will eventually reach a critical volume at which intrapericardial pressures will lead to hemodynamic collapse.

Right atrial and ventricular diastolic pressures rise as intrapericardial pressure increases. Eventually, these pressures equalize at which time the hemodynamic consequences of cardiac tamponade become clinically evident. These hemodynamic effects are best appreciated as loss of the y descent in the RA venous waveform (Figure 132-3) and the presence of a paradoxical arterial pulse. In cardiac tamponade total heart volume is fixed while the inspiratory augmentation of venous return to right sided circulation is retained. In contrast to the hemodynamics of constrictive physiology, intrathoracic pressure changes are transmitted through the pericardium in cardiac tamponade.

The y descent represents the decrease in RA pressure during passive filling of the right ventricle (RV) immediately after the tricuspid valve opens signifying the beginning of ventricular diastole. In cardiac tamponade the normal pressure gradient between the right atrium and right ventricle is lost since diastolic pressures in all four cardiac chambers are equalized causing an abbreviated and minimized decrease in RA pressure represented by a “blunted” y descent (Figure 132-4).

The paradoxical pulse or “pulsus paradoxus” is defined as a > 10 mm Hg decrease in systolic blood pressure during inspiration. The decreased intrathoracic pressure accompanying inspiration leads to increased filling of the right heart. Since total cardiac volume is fixed, this increase in right sided filling comes at the expense of decreased left heart volumes mediated through interventricular dependence or exaggerated leftward shift of the interventricular septum. Consequently, there is decreased LV filling and therefore stroke volume. The increased right sided filling does lead to increased RV stroke volume. However, several cardiac cycles are required before this causes increased LV filling. As intrapericardial pressure increases, total intracardiac volume is further diminished, and the above hemodynamic effects are accentuated, potentially leading to hemodynamic collapse (Figure 132-5).

Presentation

Pericardial effusions do not usually cause symptoms beyond those associated with any concomitant pericardial inflammation. However, cardiac tamponade commonly causes chest pain, dyspnea, or chest fullness. Additionally, symptoms of hepatic and visceral congestion, fever, fatigue, and lethargy have been reported. Importantly, these symptoms may be absent or unobtainable in patients with acute cardiac tamponade if they are in shock or critically ill. Of these symptoms dyspnea has the highest sensitivity reported in observational studies of 87% to 88%.

Physical exam findings can be helpful in the assessment of a patient with suspected cardiac tamponade. Beck's triad (hypotension, tachycardia, and distant heart sounds) was originally described in 1935 by Dr. Claude Schaeffer Beck, a thoracic surgeon. Notably, hypotension and distant heart sounds are insensitive physical findings in the assessment of cardiac tamponade. While these findings can be useful, more recent evidence based analysis of clinical, electrocardiographic, and radiographic findings are available. The presence of a paradoxical pulse, defined as a > 12 mm Hg decrease in systolic blood pressure upon inspiration has a sensitivity of 98% and a specificity of 83% with a positive likelihood ratio of 5.9. When the paradoxical pulse was < 10 to 12 mm Hg the negative LR was 0.03. In pooled analyses, elevated jugular venous pressure and tachycardia were shown to be reasonably sensitive markers (sensitivity of 76% and 77%,respectively) that, when absent, decreases the likelihood of cardiac tamponade.

The bedside evaluation of pulsus paradoxus may be initially appreciated by the disappearance of the radial pulse on inspiration. Smaller degrees of pulsus paradoxus may be noted while gradually reducing finger pressure on the radial or femoral artery similar to the gradual lowering of blood pressure from the point of obliterating the pulse to the point when only expiratory pulses are felt to the point of feeling all pulses. The accurate measurement of the paradoxical pulse is quantified using cuff sphygmomanometry, and is represented by the differences in recorded pressures between that recorded when the first Korotkoff sound is auscultated and that at which Korotkoff sounds are heard with every heart beat (Figure 132-5). Importantly, a paradoxical pulse may be absent when preexisting conditions exist that elevate LV diastolic pressures such as aortic regurgitation, LV hypertrophy, or LV failure, and conditions that limit right heart filling such as pulmonary hypertension. When cardiogenic shock develops, pulsus paradoxus may be difficult to detect. Additionally, a paradoxical pulse can be present in the absence of tamponade in patients with a multitude of disorders including COPD, asthma, pulmonary embolism, or shock.

Diagnosis

Electrocardiographic findings of low voltage, electrical alternans, and PR depression have specificities ranging from 89% to 100%, but are very insensitive findings for the diagnosis of pericardial effusions. Electrical alternans is caused by “swing” of the heart within the fluid-filled pericardium (Figure 132-6). Similarly the finding of an enlarged cardiac silhouette on chest radiography has a high sensitivity (˜89%) and low specificity (˜50%) for pericardial effusions. The cardiac silhouette may appear flask-like with “tenting” that often obscures the left heart border at the level of the left atrial appendage (Figure 132-7).

The primary diagnostic imaging modality for cardiac tamponade is transthoracic Doppler echocardiography, a noninvasive study that provides accurate information regarding the hemodynamic effects of a pericardial effusion. Echocardiography can accurately detect and quantify effusions of any size and serve as a useful tool to evaluate effusions on a serial basis. Right atrial and right ventricular collapse during early ventricular diastole signify that an effusion is severe enough to cause some degree of hemodynamic compromise. On echocardiogram, RA collapse is the most sensitive finding, while RV collapse is the most specific finding for cardiac tamponade (Figure 132-8). Importantly, large pleural effusions can also cause these findings to be present. Exaggerated respiratory variation of right and left sided venous and valvular flow patterns are highly specific for tamponade as well.

Both CT and MRI are useful adjuncts to echocardiography, providing accurate quantification of pericardial effusions and real-time imaging to quantify septal shift and chamber collapse with accuracy similar to that of echocardiography. Detailed assessment of the pericardium and the pericardial fluid, and other pathology occurring within the chest are advantages over echocardiography.

Management

Management of pericardial effusions is first determined by the presence or absence of tamponade physiology. If tamponade physiology is present the threshold for urgent pericardiocentesis should be low. The presence of cardiac tamponade should be considered a medical emergency, warranting admission to an intensive care unit with prompt consultation of a cardiovascular diseases specialist. In patients whom the decision to perform pericardiocentesis has been deferred, invasive hemodynamic monitoring with pulmonary artery catheter can be useful. Volume resuscitation is beneficial in patients with hypovolemia; however, it can be detrimental in the euvolemic or hypervolemic patient. In the absence of hypovolemia, excessive fluid resuscitation can cause increased intracardiac and pericardial pressures thus decreasing the transmural myocardial pressures and cardiac filling eventually leading to circulatory collapse. If the patient's volume status is difficult to determine, then it is reasonable to give a fluid challenge and monitor closely for clinical improvement or deterioration. The use of inotropes, specifically dobutamine, has some temporizing benefit in animal studies; however, in most patients with tamponade physiology compensatory mechanisms are already maximized.

Removal of the pericardial fluid with pericardiocentesis is the definitive treatment for cardiac tamponade. When available, pericardiocentesis is performed in the cardiac catheterization laboratory using echocardiographic guidance. In the emergent situation this may be performed blindly at the bedside. If the procedure is performed by a cardiovascular disease specialist, a pigtail catheter can be placed over a wire to facilitate further drainage of the effusion; however, this may not be possible in the emergent setting. Repeated echocardiography should be performed immediately postprocedurally to evaluate for hemodynamic improvement. The pericardiocentesis procedure is delineated in the Practice Point.

Pericardial fluid should be sent to the laboratory for analysis, including cell count with differential, hematocrit, total protein, LDH, Gram and acid fast bacilli (AFB) stains, as well as bacterial, fungal, and AFB cultures when appropriate. Additionally, cytology can be helpful if there is a suspicion of a malignant etiology. Lights criteria, commonly used to evaluate pleural effusions can be applied to determine if pericardial fluid is exudative or transudative. In the setting of pericarditis a pericardial biopsy is often required to make a diagnosis.

Long-term management involves treating the underlying pathology causing the effusion and serial echocardiography to monitor for recurrence of effusion. We recommend a repeat transthoracic echocardiogram 48 to 72 hours following initial drainage of a pericardial effusion. If there is no evidence of recurrence then further transthoracic echocardiography should be performed as clinically indicated. If there is evidence of recurrence within the first 72 hours then repeat pericardiocentesis, or more definitively, a pericardial window may be indicated, with consultative assistance from a cardiovascular disease specialist. Transudative pericardial effusions are more likely to recur and to require a pericardial window procedure performed by a cardiothoracic or thoracic surgeon. All patients diagnosed with a pericardial effusion warrant short and long term follow up with a cardiovascular disease specialist. Follow-up for two weeks following hospital discharge is indicated.

Introduction

Constrictive pericarditis is the late stage manifestation of any inflammatory process resulting in constriction and loss of elasticity of the pericardium. Any process leading to acute pericarditis can also result in constrictive pericarditis. In the developed world the three most common etiologies are postviral (idiopathic), postsurgical, and radiation induced. In less developed parts of the world tuberculosis is still a major infectious etiology of constrictive pericarditis.

Pathophysiology

Once scarring of the pericardium takes place, its intrinsic elasticity is lost. An inelastic pericardium results in restricted filling of both atria and ventricles. The stiffened pericardium effectively limits total cardiac volume causing equilibration of filling pressures in all four chambers of the heart. A consequence of this is accentuated ventricular filling during early diastole driven by elevated atrial pressures. This rapid early filling continues until mid-diastole when the ventricles reach their filling limit set by the stiffened pericardium. At this point, ventricular filling ceases and filling pressures equalize throughout the heart. The rapid early ventricular filling is represented by an accentuated y decent in both right and left atrial pressure tracings. This presents as a dominant negative wave in the already distended neck veins. The equalization of ventricular filling pressures is represented by the “square root” sign seen on diastolic ventricular pressure tracings (Figure 132-9), both of which are distinguishing features of constrictive physiology. Overall, cardiac output is decreased as a result of underfilling of the ventricles and systemic venous pressure is increased. Decreased cardiac output leads to increased sympathetic activity and upregulation of the renin-angiotensin, aldosterone-system, enhancing sodium and water retention leading to volume overload. Systemic venous pressures can be significantly increased leading to congestive hepatopathy and cachexia in advanced stages of disease. Ventricular contraction is usually preserved; however, it may be slightly diminished because of a decreased preload effect.

The decrease in intrathoracic pressure seen with inspiration is not transmitted to any of the intracardiac chambers, but is transmitted to the pulmonary vasculature. This results in a diminished filling gradient between the pulmonary veins and the left atrium causing a decrease in mitral inflow velocities and decreased filling of the left ventricle during inspiration. Consequently, RV filling is enhanced via right to left septal shift. These events are reversed during expiration. This is an important difference from the hemodynamics seen in restrictive cardiomyopathy and cardiac tamponade physiology that is useful in delineating the underlying cardiac physiology when measuring hemodynamic parameters invasively.

Effusive-constrictive pericarditis occurs when tamponade physiology occurs from a pericardial effusion in the setting of a fibrotic pericardium. Once the pericardial fluid is removed, constrictive physiology remains. The most common etiologies are malignancy, radiation therapy, connective tissue disease, and idiopathic pericarditis.

Presentation

Patients with constrictive physiology usually present with complaints of volume overload, dyspnea on exertion, and fatigue. Additionally symptoms of hepatic congestion may also be prominent, sometimes leading to the misdiagnosis of chronic hepatic disease. Important physical exam findings include the presence of Kussmal sign (lack of decline in jugular venous pressure with inspiration), which is seen only in 20% of cases. Kussmal sign can also be present in cases of severe right-sided heart failure and tricuspid valve disease. A paradoxical pulse is appreciated in 20% of cases as well. Additionally, a pericardial friction rub and pericardial knock can be present; however both are uncommon.

Diagnosis

There are no specific features on electrocardiogram to aid in the diagnosis of constrictive pericarditis. Atrial fibrillation, low voltage, and nonspecific ST-T wave changes can be seen in up to 33% of cases, however these findings are nonspecific. Chest radiography may reveal ringed calcification of the cardiac silhouette, especially on the lateral view (Figure 132-10).

Transthoracic Doppler echocardiography, a class I recommendation by the American College of Cardiology, remains a useful imaging modality to obtain valuable hemodynamic and anatomic information in the to evaluation of constrictive pericarditis. If further information is needed, evaluation with cardiac MRI can be pursued. Both cardiac CT and MRI provide direct visualization of the pericardium and allow for precise measurement of pericardial thickness. Cardiac MRI can also provide useful information regarding hemodynamics, and is considered by some to be the imaging modality of choice for pericardial diseases. In some cases the diagnosis of constrictive pericarditis cannot be made based solely on noninvasive imaging modalities. In these cases, a right and left heart catheterization is required to determine the diagnosis.

Management

Pericardiectomy is the treatment of choice for chronic symptomatic constrictive pericarditis (Table 132-2). Complete pericardiectomy (which has been likened to peeling an orange) is preferred to partial resection as recurrence rates decrease with complete resection. Additionally, patients surgically treated with complete pericardiectomy achieve more rapid normalization of hemodynamics and have lower long-term mortality rates when compared with those treated with partial pericardial resection, 83.8% versus 73.9%, respectively. Patients with very early or very advanced disease are not optimal surgical candidates because a small percentage of patients with acute pericarditis will also have some constrictive symptoms that will spontaneously resolve. The mortality associated with pericardiectomy can reach 30% to 40% in patients with advanced disease and NYHA class IV symptoms. Medical therapy with diuretics and digoxin can provide some minor clinical improvement as well. In selected patients, cardiac transplantation may be an option. In patients with tuberculous involvement, rapid treatment with appropriate antimicrobial therapy should be initiated.