Effort dyspnea and paroxysmal nocturnal dyspnea constitute the most common symptoms (Table 14–1) and provide evidence of pulmonary congestion. Because elevations
in pulmonary venous and left atrial pressures occur in the presence
of a hyperdynamic, hypercontractile left ventricle, they must be
attributed to increased stiffness of the hypertrophic ventricles.
In some patients, especially in those with volume overload, frank
pulmonary edema may be noted.
Table 14–1. Characteristic Clinical Features of Hypertrophic Cardiomyopathy. |Favorite Table|Download (.pdf)
Table 14–1. Characteristic Clinical Features of Hypertrophic Cardiomyopathy.
Dyspnea: Effort-induced, paroxysmal nocturnal, or orthopnea
Angina: Stable or unstable
Syncope: Generally following exertion
Sustained bifid apical impulse
Palpable atrial impulse (S4)
Brisk carotid upstroke
Bisferious pulse with normal pulse pressure (with LVOT obstruction)
Gallop sounds: S4 common, S3 uncommon
Ejection systolic murmur along left systolic border
Longer, higher-pitched apical systolic murmur
Effects of Valsalva maneuver: increased murmur intensity during
peak strain phase (II) and decrease in later strain-release phase (IV)
Frank syncope and presyncope (dizziness short of loss of consciousness) are common. These symptoms may be effort-related, although not predictably so, and the frequency of the episodes is highly variable. The exact
mechanism is obscure; however, it is probably related to reflex
vasodilatation and hypotension induced by stretching the left ventricular baroreceptors.
On the other hand, arrhythmia may play a role by producing a decrease
in cardiac output.
Typical effort angina simulating symptomatic coronary artery disease is frequent, although episodes of chest pain may be prolonged
and may occur spontaneously at rest. Sublingual nitroglycerin typically (but not always) fails to provide prompt relief. When the epicardial coronary arteries are large and patent, the ischemia may be due to compression of the intramyocardial coronary arteries and increased myocardial tension and muscle mass, with oxygen requirements outstripping oxygen delivery.
Palpitations may merely be the result of the patient’s awareness of forcible heartbeats, especially in the left lateral
decubitus position. Atrial and ventricular arrhythmias are more
commonly responsible. Tachyarrhythmias are poorly tolerated and
are often associated with symptoms of low output and hypotension.
Isolated or short runs of ventricular and supraventricular premature
depolarizations often occur without symptoms.
The physical signs also tend to vary considerably—from minimal or nonspecific to highly characteristic. The characteristic
signs include evidence of left ventricular hypertrophy, obstruction
of left ventricular outflow, and resistance to left ventricular
A powerful systolic thrust of the left ventricle on palpitation indicates an increase in muscle mass; although less frequent, the
characteristic bifid apex in systole is virtually diagnostic of
this condition. A prominent atrial contraction imparts a strong
presystolic impulse that is palpable at the apex. A trifid impulse
composed of a prominent a wave and bifid systolic
peaks is rarely palpable but can often be recorded on apex cardiogram. Such
a finding is highly characteristic of this disease. S4 is
commonly observed in the presence of sinus rhythm.
A jerky arterial pulse with sharp upstroke is typical, although not diagnostic. Occasionally, a bifid pulse may be felt, especially
in the carotid artery. A bifid arterial pulse in association with
a normal pulse pressure is characteristic of HOCM. The pulse contour
is influenced by the presence and severity of outflow obstruction. In
the absence of resting obstruction, the arterial pulse is essentially
normal, although with a brisk upstroke.
A systolic murmur of variable intensity is present along the left sternal border and apex. It is poorly transmitted to the aortic area
and neck vessels. It is medium- or high-pitched, with onset after
the S1. The murmur resembles a long ejection murmur along
the left sternal border and attains a regurgitant quality (high-pitched,
blowing) toward the apex. The apical murmur may be well transmitted
to the axilla. The S2 is clearly audible, and both components are
well preserved. Reverse splitting with a delayed aortic component,
when present, is diagnostic of severe outflow obstruction in the
absence of left bundle branch block. The signs of outflow obstruction,
including intensity of the systolic murmur, are accentuated by maneuvers
that augment the severity of obstruction (Table
Table 14–2. Effects of Maneuvers on Murmur Intensity and Obstruction Severity in Hypertrophic Obstructive Cardiomyopathy. |Favorite Table|Download (.pdf)
Table 14–2. Effects of Maneuvers on Murmur Intensity and Obstruction Severity in Hypertrophic Obstructive Cardiomyopathy.
|Maneuvers||Left Ventricular Outflow Obstruction||Severity of Mitral Regurgitation||Murmur Intensity|
|Amyl nitrite inhalation||↑||↑||↑|
The blowing apical murmur of mitral regurgitation also generally varies in intensity with dynamic outflow obstruction. In a few patients,
associated severe mitral valve regurgitation, independent of outflow
obstruction, may be present. Its presence can be determined by raising the
blood pressure with methoxamine or angiotensin, which—although
relieving outflow obstruction—will not diminish the murmur’s
intensity if the regurgitation is unrelated to obstruction. Because
these patients may be candidates for mitral valve surgery, this
differentiation is clinically important.
Although a prominent atrial sound (S4) is a common feature of a noncompliant hypertrophied left ventricle, a mitral
diastolic murmur simulating mitral stenosis may occasionally lead
to consideration of rheumatic mitral disease. The absence of an
opening snap and the presence of severe, unexplained left ventricular hypertrophy
should point to a correct diagnosis.
A systolic murmur of infundibular pulmonic stenosis is often prominent at the left sternal edge. The ejection sound is absent,
and the pulmonary closure sound is delayed. When infundibular obstruction
accompanies left ventricular outflow obstruction, the clinical signs
of the latter dominate. However, isolated right ventricular outflow
obstruction may be difficult to differentiate from congenital infundibular
pulmonic stenosis until evidence for unexplained left ventricular hypertrophy
A routine 12-lead electrocardiogram (ECG) often discloses evidence of left ventricular hypertrophy with increased QRS voltage or ST-T
wave changes in the lateral precordial leads (V4–V6).
Because no signs of left ventricular hypertrophy may be present
in some patients despite the massive increase in cardiac muscle
mass, a normal ECG does not exclude the diagnosis of HCM. Occasionally,
large, abnormal Q waves that simulate myocardial infarction are noted
as a result of septal depolarization. These changes of pseudo-infarction
are uncommon. Other features include a short PR interval, Wolff-Parkinson-White syndrome,
left-axis deviation from left anterior hemiblock, and complete left
or right bundle branch block. Atrial and ventricular premature depolarizations
are common, but sometimes can be detected only with ambulatory ECG recording.
Complete heart block is rare.
Deep symmetric inversion of the T waves in the precordial leads
has been described with apical HCM but may also be seen in other
types. These changes in a patient with chest pain are often mistaken
for subendocardial infarction.
Posteroanterior and lateral chest radiographs are often normal. Evidence of left ventricular enlargement may be subtle because the cavity size is not increased. Left atrial size is either normal or only
slightly increased, except in a stage of advanced decompensation. Pulmonary
venous engorgement may be seen, but frank pulmonary edema and signs
of pulmonary arterial hypertension are infrequent.
Echocardiography is the most important method for diagnosing HCM (Table 14–3). This technique is useful for evaluating the thickness of the interventricular septum
and left ventricular posterior wall and their movements in systole;
the end-diastolic and end-systolic dimensions of the left ventricular
cavity along its minor axis; the left ventricular outflow size (the space
between the anterior mitral leaflet and the interventricular septum);
and the functional aspects of mitral and aortic valve motion. It also permits differentiation of concentric and asymmetric hypertrophy.
Table 14–3. Echocardiographic Clues in Diagnosis of Hypertrophic Cardiomyopathy. |Favorite Table|Download (.pdf)
Table 14–3. Echocardiographic Clues in Diagnosis of Hypertrophic Cardiomyopathy.
Asymmetric wall thickness
Sparkling or granular appearance of walls
Normal cavity size
Dilated left atrium
Hyperdynamic LV function (EF > 70)
Systolic anterior motion of anterior (or posterior) mitral leaflet (obstructive cases)
Thickened, elongated anterior leaflet
Endocardiac thickening of LVOT
Hypodynamic basal septum
|Pulsed wave Doppler|
|Continuous wave Doppler|
The presence of dynamic left ventricular outflow obstruction is diagnosed by analyzing the systolic motion of the mitral valve.
Abnormal motion of the anterior mitral leaflet against the interventricular septum
localizes the site of outflow obstruction in HOCM. It begins sometime after
completion of early ejection and is terminated in end-systole before
aortic valve closure.
The dynamic nature of the obstruction can be interpreted from variations in the extent of the systolic anterior motion with maneuvers
designed to alter the obstruction. Patients without a resting obstruction
usually have small and incomplete SAM, whereas those with high resting gradients
tend to have a large and complete SAM that is consistently noted
from one beat to the next. Systolic anterior motion has also been
noted in hyperkinetic circulatory states, in aortic regurgitation,
during infusion of dopamine in a patient in shock, and following
mitral valve repair for myxomatous mitral valve prolapse. As a result
of the dynamic midsystolic obstruction to outflow, the aortic valve
cusps may show premature closure with late systolic reopening.
A combination of narrow left ventricular outflow space, thickened interventricular septum, and the typical SAM of the anterior mitral
leaflet is virtually diagnostic of HOCM. When the interventricular
septal wall/posterior wall thickness ratio exceeds 1.5:1.0,
asymmetric hypertrophy can be diagnosed confidently. With some exceptions,
patients with HCM demonstrate asymmetric septal hypertrophy. Two-dimensional
echocardiography may show that the asymmetric hypertrophy involves
the lateral free wall, the apex, the distal septum and, rarely, the
posteroinferior wall. Additional findings include midsystolic preclosure
of one or more aortic valve cusps, a hypodynamic interventricular
septum with diminished systolic motion, and reduced early diastolic
slope of the anterior mitral leaflet. Two-dimensional echocardiography
generally permits differentiation of SAM involving the mitral leaflet
and that involving the chordae tendineae. The leaflet SAM is more
characteristically associated with HOCM; the chordal motion may
represent passive buckling of the chordae tendineae in a rapidly emptying
left ventricle. When multiple criteria are sought, the diagnosis
can be made from the echocardiographic examination alone.
Doppler echocardiography makes it possible to obtain information on flow and pressure dynamics, using pulsed and continuous wave
modes. Pulsed wave Doppler can localize the site of obstruction
by showing high velocities in the subaortic region when the obstruction
is localized in the left ventricular outflow tract; the measurement
of high velocities by continuous wave Doppler can be used to estimate
the pressure drop across the subvalvular obstruction. The contour
of the outflow tract velocity profile mirrors the profile of the
pressure drop from the left ventricular cavity to the outflow tract and
assumes a characteristic dagger shape (Figure
14–1). As ventricular ejection begins, the early velocity
is in the range of 1.0–1.5 m/s, commensurate with
the rapid early ejection. Subsequently, the velocity progressively
increases to reach a peak in mid-to-late systole and return to baseline
at the end of ejection. This profile differs sharply from that seen
in fixed obstruction (eg, valvular aortic stenosis), where a smooth
contour of increasing velocity is observed, even when it peaks in
midsystole. The presence and severity of mitral regurgitation can
also be assessed. A similar Doppler velocity contour may also be
observed to evaluate right ventricular infundibular obstruction.
Typical dagger-shaped contour of the continuous wave Doppler velocity obtained across the left ventricular outflow tract. The peak velocity may be used to calculate gradient across the outflow tract using a modified Bernoulli equation (Peak gradient = 4 × V2).
The peak gradient in this patient (with a peak velocity of 4 m/s) is 64 mm Hg.
Doppler techniques also provide information regarding left ventricular diastolic function. The heterogenous ventricular wall relaxation
is associated with flow signals that are generally directed toward the
apex and suggest earlier relaxation of the apical than the basal
segments. These findings are also seen in other forms of hypertrophy,
however, and lack diagnostic value. The overall rate of relaxation
is prolonged, resulting in a small mitral-flow, early-filling wave.
The subsequent atrial contraction accounts for the major proportion
of ventricular filling and results in a prominent mitral inflow a wave.
These features of mitral inflow velocity pattern can be readily evaluated
by pulsed wave Doppler techniques and provide useful information. The
pulmonary venous flow pattern detected by pulsed wave Doppler provides
supplementary information. A more forceful atrial contraction results
in a more prominent retrograde flow wave into the pulmonary veins
(ar, or a reversal, wave). An
important limitation of these Doppler methods, however, is their dependence
on loading conditions and heart rate.
Cardiac Catheterization and Angiography
Before the advent of echocardiography, final confirmation of the diagnosis rested on cardiac catheterization and selective cardiac
angiography, specifically the demonstration of dynamic left ventricular
outflow obstruction. When catheterization is necessary, special
care must be taken to avoid recording an artifactual gradient caused
by entrapment of the catheter. Analysis of the recorded arterial
pressure and pressure gradient during a postectopic beat often provides
an important clue. Typically, the arterial pulse pressure is narrower
in the postectopic than in the sinus beat, in contrast to both the
normal and the fixed forms of left ventricular outflow obstruction
(eg, valvular aortic stenosis), when the pulse pressure is wider
in the postectopic beat. Accentuation of the outflow gradient with
the Valsalva maneuver, amyl nitrite inhalation, or isoproterenol infusion provides added confirmation.
Selective left ventricular cine-angiography demonstrates the characteristic anatomic and functional features of HCM. Ventricular geometry is altered, with the cavity assuming a sausage shape in
the right anterior oblique projection. In a few patients, simultaneous
left and right ventricular angiograms have demonstrated a massively
thickened interventricular septum, especially in its midportion.
Such techniques, however, are no longer routinely used because echocardiography provides
a reliable, noninvasive diagnostic tool. Therefore, catheterization-angiography
studies should be reserved for selected patients and used on rare occasions
for diagnostic confirmation.