Hypertrophic cardiomyopathy

ECG 1A: Sinus rhythm; pattern of left ventricular hypertrophy (positive Sokolow index), right bundle branch block (QRS of 125 ms, rSr’ pattern in V1), narrow and deep q waves in leads I and aVL; negative T waves in leads I, II, aVL, V5, V6;

Patient 2: Brother (37 years old) of patient 1;

ECG 1B: Sinus rhythm; bifid P wave in leads I, II, III, aVF, V5, V6; increase in R wave voltage in V2-V6; negative T waves in V4 to V6;

Patient 3: Second brother (32 years old) of patient 1;

ECG 1C: Sinus rhythm; narrow q waves in leads I, II, III, aVF, V4, V5, V6; increase in R wave amplitude in V4, V5, V6;
These three tracings illustrate the different electrical abnormalities that can be observed in patients with hypertrophic cardiomyopathy and show that, for a same mutation, electrocardiographic changes may vary.

Patient 4: 54-year-old patient with hypertrophic cardiomyopathy;

ECG 1D: Sinus rhythm with pathological P wave pattern (prolongation of its duration, clear biphasic pattern); relatively short PR interval with no pre-excitation pattern; left ventricular hypertrophy and lateral repolarization disorders;

Patient 5: 47-year-old patient with asymmetric hypertrophic cardiomyopathy with a considerable increase in septal thickness (48 mm);

ECG 1E: Wide and notched Q waves in leads I, aVL, V5, V6 associated with increased R wave amplitude in V1 and V2; these abnormalities are directly linked to the hypertrophy of the septum;

Comments: Hypertrophic cardiomyopathy is an inherited disorder (even if there are sporadic forms) which is characterized by the presence of hypertrophy that occurs in the absence of contributory factors such as hypertension or aortic stenosis. More than 150 localized mutations in the genes encoding sarcomeric membrane proteins have been described which explains the significant heterogeneity in clinical and electrocardiographic phenotype. Transmission is generally autosomal dominant with variable penetrance. Hypertrophy is most often asymmetric, preferentially affects the interventricular septal wall, although the degree and distribution of the hypertrophy varies from patient to patient and is associated with an abnormal systolic movement of the mitral valve, which can cause a dynamic obstruction, albeit inconsistently, of the left ventricular outflow tract (approx. 25% of cases). A diastolic dysfunction is common resulting from impaired relaxation and filling by a rigid and hypertrophied ventricular myocardium. The change in tissue architecture favors the occurrence of ventricular arrhythmias, with hypertrophic cardiomyopathy representing the first cause of sudden death in young patients.

The diagnosis of hypertrophic cardiomyopathy is suggested by a familial context and signs and symptoms which are confirmed by cardiac ultrasound or MRI. The electrocardiogram is rarely normal, the hypertrophy conferring frequently typical patterns which is an important element of the diagnosis. While electrical abnormalities are the rule, no electrocardiographic sign is pathognomonic and there is no electrocardiographic pattern characteristic of a given mutation. The most frequent electrical signs are abnormalities of the QRS complex with virtually constant left ventricular hypertrophy translated by a marked increase in R wave voltages, abnormal q waves, deep conduction disturbances, and systolic overload-type repolarization disorders.

• Rhythm remains mostly sinus even if episodes of atrial fibrillation are described in approximately 10% of patients generally at advanced stages of the disease;
• Diastolic dysfunction can lead to enlargement of the left atrium (widened P wave) and/or right atrium (increase in voltages);
• Atrioventricular conduction is usually preserved; in less than 10% of cases, the electrocardiogram reveals a prolongation of the PR interval; conversely, a short PR interval with accelerated nodal conduction can be observed;
• Left ventricular hypertrophy is the most frequent electrical sign; it is reflected by the increase in R wave voltage in the left and frontal precordial leads (leads I and aVL) with delayed intrinsicoid deflection; different criteria are used to define and quantify hypertrophy: Sokolow index (SV1 + RV5 or RV6 ≥ 35 mm), R wave in AVL ≥ 12 mm, Cornell index (R wave in AVL + S wave in V3 ≥ 20 mm in women and ≥ 28 mm in men);
• Abnormal, deep, narrow q waves (< 40 ms, dagger-shaped) can mimic a sequela of myocardial necrosis; they are frequent (50% of cases) and reflect hypertrophy of the septum when observed in the posterolateral leads; they can vary both in their topography (sometimes very localized or sometimes diffuse including anteroapical leads) and morphology (sometimes wide and notched);
• Signs of right ventricular hypertrophy are rarer (less than 15% of cases) and result in relatively large R waves in right precordial leads;
• Repolarization disorders are common, with hypertrophy accompanied by ST segment and T wave abnormalities, which sometimes assume a pseudo-ischemic aspect due to the depth and symmetry of the inverted T waves;
• Incomplete left bundle block-type conduction disorders are relatively rare with the exception of left incomplete bundle blocks which may explain the disappearance of the q waves in the lateral territory;

Take-home message: The combination of left ventricular hypertrophy, deep q waves and repolarization disorders should evoke the diagnosis of hypertrophic cardiomyopathy.