11/14. Afterdepolarizations as a mechanism for the long qt syndrome: electrophysiologic studies of a case.A young woman with palpitation and syncope was found to have ventricular tachyarrhythmia and a congenital long QT interval. The QT interval was shortened and the arrhythmia suppressed by propranolol. Electrograms recorded at various sites in both ventricles revealed a distinct diastolic slow wave that followed the T wave and measured 1.1 mV. Epinephrine infusion and emotion augumented this diastolic wave and induced ventricular ectopic complexes arising from this potential. Similar endocardial recordings in eight patients without a long QT interval showed diastolic slow waves that never exceeded 0.28 mV. In normal canine myocardium, afterdepolarizations can be induced by norepinephrine and blocked by propranolol. These findings suggest that the long qt syndrome is associated with abnormally large afterdepolarizations in ventricular myocardial cells, which are enhanced by beta-adrenergic stimulation to attain threshold and produce firing.- - - - - - - - - - ranking = 1keywords = motion (Clic here for more details about this article) |
12/14. Total disconnection of the right ventricular free wall: surgical treatment of right ventricular tachycardia associated with right ventricular dysplasia.arrhythmogenic right ventricular dysplasia is a myopathy that affects the right ventricular free wall (RVFW) and gives rise to recurrent reentrant ventricular tachycardia (VT). Because the entire right ventricle is potentially arrhythmogenic, ablating a single site of VT may not eliminate the arrhythmia. We developed an operation to confine any arrhythmic activity arising from the right ventricle to that chamber: total disconnection of the RVFW from the left ventricle. We performed RVFW disconnection in two patients with refractory VT associated with arrhythmogenic right ventricular dysplasia. At least two sites or origin of morphologically distinct VT were identified in the RVFW in each patient. RVFW disconnection was carried out under normothermic cardiopulmonary bypass. An encircling incision was made along the attachment of the RVFW to the aortoventricular unit and the tricuspid annulus; the right coronary artery and its RVFW branches were left intact. Electrical activity of the two chambers became dissociated, and VT arising from the RVFW was confined to that chamber. Postoperatively, there was no clinical evidence of hemodynamic impairment (follow-up 4 months and 3 months). Left ventricular function was unchanged and right ventricular flow was maintained by atrial contraction and motion of the septum toward the RVFW during left ventricular systole. One patient had incessant right ventricular tachycardia confined to the RVFW for 3 weeks. We conclude that RVFW disconnection is feasible and applicable to patients with refractory VT originating in the diffusely diseased RVFW.- - - - - - - - - - ranking = 1keywords = motion (Clic here for more details about this article) |
13/14. Cardiac manifestations of malignant hyperthermia susceptibility.malignant hyperthermia is a disease resulting from defective cellular membranes, usually presenting as drug-induced pyrexic crises. We describe four patients with life threatening ventricular arrhythmias or chest pain in the absence of pyrexic crises. Three presented with life threatening arrhythmias and the fourth with severe atypical chest pain. Two patients had a family history of multiple sudden deaths. Resting CKs were elevated in three patients while CK-MB was elevated in one. Resting ECGs were abnormal in three. Three patients had recurrent ventricular tachycardia, two had recurrent ventricular fibrillation and multiple cardiac arrests. cardiac catheterization showed abnormal left ventricular wall motion in two and minimal mitral valve prolapse in one while all had normal coronary arteries. thallium-201 myocardial imaging demonstrated large perfusion defects in the patient with electrocardiographic Q waves and normal coronary arteries. Myocardial involvement has been demonstrated by clinical, electrocardiographic, hemodynamic, angiographic and myocardial imaging abnormalities. Malignant arrhythmias occurred in these patients in the absence of pyrexic crises or drug admininstration. Abnormal calcium release in the myocardium, as documented in skeletal muscle membranes, may be a unifying concept for the various manifestations described.- - - - - - - - - - ranking = 1keywords = motion (Clic here for more details about this article) |
14/14. Echocardiographic features of second degree atrioventricular block.Echocardiographic studies demonstrated abnormalities of motion of the pulmonary valve, the aortic root and valve, the mitral and tricuspid valves, the left ventricle, and the left atrium in two patients with second-degree atrioventricular block. During Wenckebach 3:2 atrioventricular conduction, ventricular beats exhibited alternately long and short periods of systolic opening of the pulmonary and aortic valves and alternately large and small left ventricular stroke volumes. During 4:3 and 3:2 Wenckebach atrioventricular conduction, the left ventricular stroke volume was directly proportional to the preceding end-diastolic volume. During 2:1 atrioventricular conduction, the blocked atrial contractions may produce movements of the left atrial wall, thereby revealing the true atrial rate when the blocked P waves are obscured in the electrocardiogram by their superimposition on preceding T waves.- - - - - - - - - - ranking = 1keywords = motion (Clic here for more details about this article) |
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