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To determine the independent effects of left bundle branch block (LBBB) on global and regional left ventricular (LV) function we performed equilibrium radionuclide angiocardiography at rest in 3 patients with chronic LBBB (group I, mean age 53.6 years and in 6 patients with intermittent LBBB (group II, mean age 41.5 years). All patients were judged to have an apparently normal heart. In 2 of 3 patients of group I a LV ejection fraction lower than 50% was observed, and in all 3 patients septal motion abnormalities were present. In all patients of group II the global LV ejection fraction was normal during normal conduction and decreased during LBBB; the inferoapical regional ejection fraction decreased in 5 of 6 cases and the posterolateral regional ejection fraction in 3 of 6 cases. Moreover, septal hypokinesis was observed both during normal and abnormal conduction in all group II patients. These findings seem to confirm that LBBB, chronic or intermittent, is able to deteriorate LV performance at rest, even in patients with an otherwise normal heart.

Ambulatory electrocardiographic monitoring (AEM) was performed in 22 patients (range 13–62 years; mean age 38.2 ± 12.7) with grades I, II and III of myotonic dystrophy in order to evaluate the occurrence of potentially dangerous cardiac arrhythmias and conduction disturbances. All patients had previously undergone echocardiographic examination to determine whether structure and function abnormalities were present. In 6 patients with normal resting electrocardiogram, AEM revealed: first degree A-V block (4 cases), class IVa Lown ventricular arrhythmias (3 cases) and episodes of atrial fibrillation (4 cases). In 2 of 3 cases with abnormal scalar electrocardiogram new abnormalities (first degree A-V block and further prolongation of P-R interval) were demonstrated by AEM. Only 1 patient had mild signs of left ventricular dysfunction at echo. Disorders of cardiac conduction and rhythm are characteristic of myotonic dystrophy and can predispose to severe cardiac events. In this respect AEM is shown to be an early and sensitive tool in identifying patients at risk.

To determine the occurrence of familial and sporadic forms of hypertrophic cardiomyopathy (HC) 74 first-degree relatives of 21 patients with proven HC were studied by M-mode and two-dimensional echocardiography. A diagnosis of HC was made in 11 relatives (15%) while it was excluded in 61 of them (82%); 2 subjects (3%) were considered neither affected nor unaffected (borderline left ventricular hypertrophy suggestive of HC). Inspection of pedigrees revealed 38% of familial forms of HC with an autosomal dominant pattern of inheritance in 5/8 families (62%). Furthermore, among those relatives judged unaffected by means of full echocardiographic criteria for HC, an attempt was made to find out whether minor changes of left ventricular geometry were present for their possible implications in genetics of HC (latent or potential forms, low phenotypic expression of the disease). Eleven out of 61 unaffected relatives had a left ventricular wall thickness radius ratio > .50 (equivocal hypertrophy), a value that was higher than two standard deviations of the control group. Assessment of clinical significance of borderline and equivocal hypertrophy in relatives of patients with HC is required for a better understanding of genetic transmission of this disease. In this view the occurrence of sporadic and familial forms of HC might be revisited.