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eFigure 10–28. First-degree atrioventricular (AV) block. The PR interval is prolonged to 0.28 s. The laddergram beneath the ECG illustrates the three levels of AV conduction: the atrium, the AV node, and the ventricles, with the delay in AV conduction represented as occurring in the AV node. Reproduced with permission from Jason E. Roediger, CCT, CRAT. ECG Guru Instructor Resources. https://www.ecgguru.com/blog-ecg-challenge-week-june-24-%E2%80%93-july-1-2012-pinpoint-primary-disturbance. A 12 lead electrocardiograph shows the rhythmic tracing observed in a case of first degree A V block.

Current Medical Diagnosis & Treatment 2025 > Chronic Stable Angina Pectoris (Chronic Coronary Syndromes)

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eFigure 10–41. Type I second-degree AV block—classic Wenckebach. There is progressive PR prolongation until failure of conduction. The incremental increase of the PR interval (Δ) is less with each successive complex, which explains the progressively shorter R-R intervals. The R-R interval containing the nonconducted P wave (1340 msec) is less than twice the baseline P-P interval (1600 msec). Note the mathematical relationship between this interval and the Δ measurement, 1340 = 1600 − (120 80 60). (Reproduced with permission from Zimmerman FH. Atrioventricular Conduction Abnormalities. ECG Core Curriculum. New York, NY: McGraw Hill, LLC; 2023.) An electrocardiogram and a laddergram reveal a type 1 second degree atrioventricular block.

Current Medical Diagnosis & Treatment 2025 > Acute MI with ST-Segment Elevation

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eFigure 10–42. Mobitz type II second-degree AV block. Intermittently P wave fails to conduct but not preceded by prolongation of PR interval. (Reproduced with permission from Vijayalakshmi IB, Rao PS, Chugh R, eds. A Comprehensive Approach to Congenital Heart Disease. Jaypee Brothers Medical Publishers; 2013.) A 12 lead electrocardiograph shows the rhythmic tracing as observed in a case of type 2 second degree A V block.

Current Medical Diagnosis & Treatment 2025 > Acute MI with ST-Segment Elevation

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eFigure 12–6. Short PR. Normal P wave with PR interval < 0.12 sec. A 31-year-old woman came to the emergency department following an episode of syncope consistent with vasovagal type. She has no history of palpitation or documented tachycardia. Her previous ECG had similar pattern. The possible etiologies of short PR interval are rapid conduction in an anatomically normal AV node, conduction through fast pathway, paranodal fiber, conduction bypasses most or all of the AV node, and small, underdeveloped AV node. Lown-Ganong-Levine syndrome includes (1) PR interval < 0.12 second, (2) normal P wave, (3) normal QRS duration, and (4) documented paroxysmal supraventricular tachycardia. A 12 lead electrocardiograph shows a rhythmic tracing with a short P R interval in lead 2.

Current Medical Diagnosis & Treatment 2025 > PSVT Due to Accessory AV Pathways (Preexcitation Syndromes)

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eFigure 12–7. A: ECG at initial preparticipation physical evaluation (preablation) demonstrates a WPW pattern. Red arrows identify the characteristic delta wave and short PR interval. B: Postablation ECG. WPW pattern has been extinguished. Note the absence of a delta wave and normalization of the PR interval. New T wave inversion in the inferior leads is a result of the ablation therapy that typically resolves over time. WPW, Wolff-Parkinson-White. (Reproduced with permission from Rao AL, Salerno JC, Asif IM et al. Evaluation and management of Wolff-Parkinson-White in athletes. Sports Health. 2014;06(04):326–332.) A 12 lead electrocardiograph shows a rhythmic tracing with a classic W P W pattern. A 12 lead electrocardiograph shows the rhythmic tracing observed post ablation.

Current Medical Diagnosis & Treatment 2025 > PSVT Due to Accessory AV Pathways (Preexcitation Syndromes)

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eFigure 12–7. A: ECG at initial preparticipation physical evaluation (preablation) demonstrates a WPW pattern. Red arrows identify the characteristic delta wave and short PR interval. B: Postablation ECG. WPW pattern has been extinguished. Note the absence of a delta wave and normalization of the PR interval. New T wave inversion in the inferior leads is a result of the ablation therapy that typically resolves over time. WPW, Wolff-Parkinson-White. (Reproduced with permission from Rao AL, Salerno JC, Asif IM et al. Evaluation and management of Wolff-Parkinson-White in athletes. Sports Health. 2014;06(04):326–332.) A 12 lead electrocardiograph shows a rhythmic tracing with a classic W P W pattern. A 12 lead electrocardiograph shows the rhythmic tracing observed post ablation.

Current Medical Diagnosis & Treatment 2025 > PSVT Due to Accessory AV Pathways (Preexcitation Syndromes)

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