Andersons pediatric cardiology 1650

ejection murmur that reflects the degree of subaortic obstruction As discussed earlier, the auscultatory finding in HCM may be modified through physiologic manipulation Decreases in ventricular volume or blood pressure as well as increases in contractility (e.g., Valsalva, exercise) may increase the murmur's intensity, while manipulations producing the opposite effects may reduce the murmur (e.g., squatting) Electrocardiography The 12-lead ECG is commonly abnormal in patients with HCM; however, the findings may be nonspecific and lead to confusion in specific population such as highly trained athletes.236 Increased left ventricular voltage may be present, but the finding is variable and inconsistently related to the degree of ventricular hypertrophy (sensitivity 30% to 40% in phenotype-positive patients).237,238 Nonvoltage abnormalities are more common, including pathologic Q-waves, left-axis deviation, ST-T wave abnormalities, and t-wave inversion These are more common than hypertrophy and show better sensitivity and specificity for the presence of phenotypic disease, but they are not predictive of clinical outcome (Fig 61.2).237,238 Giant T-wave inversion may be seen in apical HCM FIG 61.2 Electrocardiographic patterns in hypertrophic cardiomyopathy (A) 12-lead echocardiogram (ECG) from an 8-year-old with hypertrophic obstructive cardiomyopathy Note the Q-waves in the inferior and lateral precordial leads, ST-segment abnormalities, and voltage criteria for biventricular hypertrophy (B) 12-lead ECG from a 14-year-old with hypertrophic obstructive cardiomyopathy Note the diffuse ST- and T-wave abnormalities and evidence of hypertrophy The ECG may also provide diagnostic insight into the cause of ventricular hypertrophy A short-PR and ventricular preexcitation pattern may be seen in patients with Pompe disease, PRKAG2, and Danon disease as well as mitochondrial disease A short PR without preexcitation may also be present in patients with Fabry disease, whereas older patients may develop PR prolongation and atrioventricular block Extreme hypertrophy may be seen in both Pompe and Danon disease Atrioventricular conduction delay may be seen in mitochondrial disease and PRKAG2 disease Ambulatory electrocardiography (typically every 1 to 2 years) is recommended for patients at the time of initial evaluation and for the detection of asymptomatic atrial and ventricular arrhythmia as well as to help guide decisions on implantable cardioverter-defibrillators (ICD) candidacy.6,7,239 Echocardiography Assessment of myocardial dimension and hypertrophy is required to make the diagnosis of HCM (as defined by a z-score greater than +2) and to help distinguish nonpathologic ventricular hypertrophy (e.g., athlete's heart) Although the early definitions of HCM required asymmetric septal hypertrophy (1.3 : 1, septal-to–free wall ratio), the development of cross-sectional imaging has revealed that the pattern of hypertrophy can be quite variable (e.g., asymmetric anteroseptal hypertrophy, concentric hypertrophy, apical hypertrophy) (Fig 61.3) The variable nature of hypertrophy underscores the importance of adequate visualization of all cardiac segments to rule out segmental hypertrophy FIG 61.3 Echocardiographic patterns of hypertrophic cardiomyopathy (A) Parasternal long-axis view of a 13-year-old with severe asymmetric septal hypertrophy (B) Parasternal short-axis view of the same patient (C) Parasternal short-axis view from a 12-year-old with concentric left ventricular hypertrophy (D) Parasternal short-axis view from a 14-year-old with an eccentric distribution of left ventricular hypertrophy There may be a systolic intracavitary gradient in selected patients, whereas dynamic outflow tract obstruction with systolic anterior motion of the mitral valve may be suggested by two-dimensional echocardiography and confirmed using M-mode echocardiography (Fig 61.4) Turbulent flow and dynamic obstruction in the LVOT may also be visualized by fluttering of the leaflets and