but remain controversial.69–73 These criteria are based generally on echocardiography or cardiac MRI findings of an increased ratio of trabeculations to compact myocardium. These criteria have been called into question recently for being non-specific, particularly among black individuals who have relatively greater degrees of myocardial trabeculations and among athletes.74 Abnormal ECG findings in isolated LVNC ECG abnormalities in isolated LVNC are common but nonspecific (figures 17 and 18). In a series of 78 patients with a clinical diagnosis of LVNC, only 13% had a normal ECG.75 The most common abnormalities in this series included repolarisation changes (72%), QT prolongation (52%), ST segment depression (51%), TWI (41%), LVH voltage criteria (38%), IVCD (31%) including LBBB (19%) and RBBB (3%), and LAE (26%).75 Given the overlap of some of these findings with physiological ECG changes found in athlete’s heart, abnormal ECG criteria requiring additional evaluation to rule out an underlying cardiomyopathy are listed in table 1. Evaluation of suspected isolated LVNC Echocardiography is usually the first investigation in the evaluation of ECG abnormalities suggestive of cardiomyopathy. The diagnosis and evaluation of suspected LVNC is quite challenging, and therefore patients should be referred to a cardiovascular specialist familiar with LVNC. Cardiac MRI provides a more detailed and accurate assessment of myocardial trabeculations and is recommended in cases with concerning or borderline findings on echocardiography. A smaller absolute thickness of compacted myocardium and the presence of LV dysfunction favour the diagnosis of LVNC. In select cases, LV angiography may be used to help delineate hypertrabeculation from compacted myocardium. Holter monitoring or more extended ambulatory monitoring for arrhythmias also should be diagnostic evaluation. Other ECG findings possibly suggestive of a cardiomyopathy Several additional ECG abnormalities including RBBB, nonspecific IVCD with QRS duration <140 ms, and isolated (one per tracing) ectopic/premature ventricular contractions (PVCs) have been associated with an underlying cardiomyopathy in non-athletic populations.76–83 However, these findings are also more common in trained athletes without an underlying heart disease than among the general population.26 84–87 Each of these findings, particularly when observed in an asymptomatic athlete with no family history Figure 19. ECG showing complete right bundle branch block with an R0 wave in V1, terminal S wave in V6, and a QRS duration of 128 ms. nummer 4 | september 2013 | Sport & Geneeskunde 35 suggestive of heritable heart disease, has a low-positive predictive value for the cardiomyopathic conditions associated with an increased risk of SCD during exercise. As such, none of these ECG patterns, when found in isolation in asymptomatic athletes, clearly necessitate further evaluation. However, in athletes with cardiovascularrelated symptoms or a family history of sudden death or suspected cardiomyopathy, each of these findings should prompt additional evaluation to evaluate for cardiomyopathy. Right bundle branch block RBBB is defined as a QRS complex ≥120 ms in association with a terminal (final component of the QRS complex) R0 wave in lead V1 and terminal S waves in leads I, aVL and V6 (figure 19). The R0 may extend into lead V2 but is typically absent in other precordial leads. Twaves in typical RBBB are in the same direction as the terminal QRS forces and are thus inverted in leads with an R0 (V1±V2). A QRS complex duration of 100–119 ms with these morphological features is termed an incomplete RBBB. Although RBBB may be present in various forms of heart disease, complete and incomplete RBBB are found commonly among trained athletes without underlying heart disease. This ECG pattern has been shown to reflect the exercise-induced right ventricular remodelling common in endurance sport athletes. 88 In asymptomatic athletes with an isolated complete or incomplete RBBB, no further diagnostic evaluation is required. In contrast, athletes presenting with symptoms suggestive of cardiomyopathy, a family history of sudden death or suspected cardiomyopathy, an RBBB with atypical features (extensive TWIs, ST-segment Pagina 34
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