A Visual Guide to ECG Interpretation

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A VISUAL GUIDE TO ECG INTERPRETATION

Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy (HCM) is an autosomal dominant genetic disorder most often caused by mutations in genes that encode proteins in the cardiac sarcomere. In some cases, this cardiomyopathy is caused by other genetic disorders such as Friedrich ataxia (Fig. 9.4).

Hypertrophic Patterns Hypertrophy is frequently diffuse but can be limited to segmental areas of the left ventricle. There is no classic hypertrophic pattern.

Dominant and partially unopposed LV activation

ECG Findings

Thickened septum

Deep Q waves in II, III, aVF, V5, and V6, especially in patients who are in teenage years, may be the most specific finding in HCM. LVH and its associated repolarization abnor malities are the two most common abnor malities. 5 The magnitude of voltage does not predict the extent of hypertrophy. 6 Giant negative T waves in the precordial leads occur when hypertrophy is localized in the apex.

LV free wall

Q Waves

V6

Left Ventricular Hypertrophy

Left-to-right septal depolarization

RV free wall B FIGURE 9.4 ( A ) Vector forces in hypertrophic cardiomyopathy. ( B ) Resultant QRS morphology. A

Giant TWI

Patients may be asymptomatic or may complain of dyspnea on exertion, angina, presyncope, or syncope. Syncope may result from outflow tract obstruction or dysrhythmias.

Clinical Presentations

Clinical Complications

Occur in up to 38% of patients. 7

Supraventricular Dysrhythmias

Ventricular Dysrhythmias

Asymptomatic nonsustained ventricular tachycardia occurs in 25% of adult with HCM. 7,8

Structural abnormalities of the mitral valve apparatus are common in HCM. Abnormal papillary muscle and mitral valve leaflets contribute to left ventricular outflow tract obstruction. Obstruction can also occur in the left ventricular midcavity. Diastolic dysfunction is common in patients with HCM, and Doppler imaging is recommended as a routine diagnostic study in patients with HCM. 9 Some patient with apical or distal LVH may develop apical scarring or aneurysm. This may cause coved ST segment elevation in the lateral precordial leads. Copyright © 2021 Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited.

Outflow Tract Obstruction

Diastolic Dysfunction

Apical Aneurysm

Infective Endocarditis

Occurs in patients with outflow tract obstruction. Antibiotic prophylaxis is recommended for invasive procedures.

ICDs are recommended for secondary prophylaxis in patients who survive VF or sustained VT. Primary prevention of sudden cardiac death with an ICD is reserved for patients who are considered high risk based on 48-hour ambulatory ECG monitoring, 2D Doppler echocardiogram, and history. 9

Sudden Cardiac Death