(Vi). Ventricular premature contractions were readily produced; ventricular couplets and short runs of ventricular tachycardia were occasionally elicited. The probability of a stretch-induced arrhythmia was determined from multiple alternating sequences in which a stretch of known amplitude (AV) or no stretch was delivered. As AV was increased, the probability of a stretch-induced arrhythmia was low initially, increased sharply after a threshold was exceeded, and approaching 100% with physiological volumes. With V; set to a standard value of 20 ml, corresponding to end-diastolic pressure of 5.3±5.2 mm Hg (mean± SD), the AV resulting in a 50%o chance of a stretch-induced arrhythmia (MV50) was 15.0±+1.6 ml. A decline in AV50 was consistently observed when V; was increased. While AV50 values were remarkably similar (10.7% coeffilcient of variation), the pressure at the time the ventricular premature depolarization was triggered was highly variable for different ventricles; this finding suggests that myocardial strain is more important than absolute level of wall stress in the initiation of these arrhythmias. These results demonstrate that myocardial stretch predictably initiates arrhythmias and that the susceptibility to stretch-induced arrhythmias is enhanced by ventricular dilatation. Thus, ventricular ectopy in patients with regionally or globally dilated hearts may arise, in part, by a mechanism of myocardial stretch. (Circulation 1990;81:1094-1105 It is commonly accepted that serious ventricular arrhythmias are caused by abnormalities in impulse formation and conductionl,2; however, these important electrophysiological mechanisms fail to explain why lethal arrhythmias most commonly arise in patients with severe heart failure and dilated ventricles.3-7 A number of factors predispose such patients to arrhythmias. Structural abnormalities, es-

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The use of laser lead extraction (LLE) to remove pacemaker or implantable cardioverter-defibrillator leads has become increasingly prevalent. This advanced technique has been shown to be highly effective and safe. We report a rare case of severe traumatic tricuspid regurgitation after LLE that led to death.

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