“…In most patients the balloon deformity has little haemodynamic consequence but the condition has been associated with ventricular and supraventricular arrhythmias (Hancock and Cohn, 1966;Kreisman et al, 1971;Gooch et al, 1972;Sloman, Wong, and Walker, 1972;Jeresaty, 1973;Rizzon et al, 1973;DeMaria et al, 1974;Gulotta et al, 1974;Schaal, Fontana, and Wooley, 1974;Winkle et al, 1975), and sudden death has been reported in 9 patients (Hancock and Cohn, 1966;Barlow et al, 1968;Trent et al, 1970;Jeresaty, 1973;Marshall and Schappell, 1974;Rakowski et al, 1975). The incidence of the lesion is not known accurately but in a recent necropsy series the abnormality was detected in 0'33 per cent of the population studied (Rizzon et al, 1973), and clinical reports have suggested incidences from 6 to 10 per cent (Markiewicz et al, 1975;Brown, Kloster, and DeMots, 1975;Procacci et al, 1975).…”