Termination of ventricular tachycardia. Evaluation of a new pacing method.

Ventricular extrastimuli or rapid ventricular pacing used to terminate ventricular tachycardia (VT) may be ineffective or may accelerate VT. Therefore, a new method to facilitate termination of VT and decrease the incidence of acceleration was evaluated. The new method utilized rapid ventricular pacing at cycle length 10 to 100 ms shorter than VT cycle length with the introduction of 1 or 2 ventricular extrastimuli.

The incidence and clinical significance of epicardial late potentials in patients with recurrent sustained ventricular tachycardia and coronary artery disease.

Seventy-eight patients with ventricular tachycardia associated with coronary artery disease underwent intraoperative mapping while in sinus rhythm to evaluate the frequency and significant of late potentials. In 30 of these patients, the surface ECG was subjected to signal averaging to correlate the incidence and duration of low-amplitude, delayed electrograms with the presence of late potentials recorded during epicardial mapping. One to four epicardial late potentials were observed in nine patients (11.

Electrophysiologic study for ventricular arrhythmia: effect on total and myocardial-specific creatine kinase activity.

To determine the potential for myocardial injury during electrophysiologic study for ventricular arrhythmia, total creatine kinase and creatine kinase B-subunit enzyme activity were serially measured after the procedure in 24 patients. During electrophysiologic study 14 of the 24 patients had sustained ventricular tachycardia or fibrillation, 4 patients had nonsustained ventricular tachycardia, and 6 patients had no ventricular arrhythmia induced. Cardioversion was necessary because of hemodynamic collapse in 9 of the 14 patients with sustained ventricular tachycardia or ventricular fibrillation.

Amiodarone for control of sustained ventricular tachyarrhythmia: clinical and electrophysiologic effects in 51 patients.

We evaluated the electrophysiologic effects of amiodarone and its ability to control ventricular arrhythmia in a selected group of 51 patients with refractory sustained ventricular arrhythmia. Amiodarone in doses of 400 to 800 mg/day prolonged refractoriness in the atria, atrioventricular (AV) node, and ventricle as well as conduction through the AV node and His-Purkinje system. Although it had no effect on measurements of sinus nodal function (sinus nodal recovery time and sinoatrial conduction time), it prolonged the sinus cycle length and 2 patients required a permanent pacemaker for symptomatic sinus bradycardia.

Arrhythmia prophylaxis using propranolol after coronary artery surgery.

Sixty patients undergoing coronary artery bypass grafting operations with cold potassium cardioplegia as the method of myocardial preservation either received low-dose oral propranolol (10 mg every 6 hours; 28 patients) or served as controls (32 patients). The study period began after extubation and ended at the time of hospital discharge. On the fourth postoperative day, 24-hour Holter monitoring was performed to assess additional subtle differences in arrhythmias.

Electrocardiographic changes following endocardial resection for ventricular tachycardia.

The ECG changes resulting from endocardial resection, with or without aneurysmectomy and coronary artery bypass grafting (CABG), are reported in 82 patients. Angiographic and surgical features and peak creatine kinase (CK) levels are correlated with ECG findings. Twenty-three of 82 patients (28%) had the following ECG changes postoperatively: decreased ST segment elevation = 3 (4%), loss of R wave amplitude = 4 (5%), increased R wave amplitude = 5 (6%), new Q wave = 4 (4%), axis shift greater than or equal to 45 degrees = 6 (7%), and new bundle branch block = 6 (7%).

Reproducibility of equilibrium radionuclide ventriculography in patients with coronary artery disease: response of left ventricular ejection fraction and regional wall motion to supine bicycle exercise.

To evaluate the reproducibility of ejection fraction (EF) and regional wall motion (RWM) analyses by rest and exercise equilibrium radionuclide ventriculography (RNV) in the presence of coronary artery disease (CAD), 18 patients underwent two maximum, multistage supine bicycle exercise studies separated by an interval of 2 weeks. There were no significant differences in EF between the two studies, both at rest (56.0 +/- 13.

Disturbance of pulmonary prostaglandin metabolism in fetuses of alloxan-diabetic rabbits.

[14C]Arachidonic acid conversion in lung homogenates of 28-day fetuses from control and alloxan-diabetic rabbits was studied. The major metabolites were 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid and prostaglandin E2. Small amounts of 6-ketoprostaglandin F1 alpha, prostaglandin F2 alpha, and thromboxane B2 were also observed.

Ventricular activation during ventricular endocardial pacing. II. Role of pace-mapping to localize origin of ventricular tachycardia.

Intraoperative pace-mapping has been proposed as a method of identifying the origin of ventricular tachycardia; however, both epicardial activation and electrocardiographic configuration have limitations in localizing the origin of ventricular tachycardia. Because most ventricular tachycardias associated with ischemic heart disease appear to arise near the endocardium, this study evaluated the ability of bipolar catheter endocardial pacing at or near the endocardial site of origin of spontaneous ventricular tachycardia to mimic the QRS configuration of the spontaneous tachycardia. Twelve patients were studied who had ventricular tachycardia whose origin was determined with catheter endocardial mapping.

Ventricular activation during ventricular endocardial pacing: I. Electrocardiographic patterns related to the site of pacing.

The QRS configuration produced by pacing at multiple left ventricular endocardial sites was evaluated in eight patients with (group 1) and six patients without (group 2) left ventricular wait motion abnormalities. Pacing was performed at a total of 122 sites, 4 to 13 sites in each patient. The QRS configuration resulting from apical pacing locations was compared with that at basal, septal to lateral and inferior to superior locations.

Long-term results of endocardial resection for sustained ventricular tachycardia in coronary disease patients.

Sixty patients with recurrent sustained ventricular tachycardia (VT) refractory to medical therapy underwent subendocardial resection. There were 52 men and 8 women, ranging in age from 39 to 74 years, all of whom had coronary disease. Each patient had had a prior infarction 1 week to 11 years prior to surgery and 52 had left ventricular aneurysms.

Noninvasive detection and localization of coronary stenoses in patients: comparison of resting dipyridamole and exercise thallium-201 myocardial perfusion imaging.

Two noninvasive tests to detect and localize coronary stenoses were compared in a fully blinded protocol. Thallium201 myocardial perfusion imaging (MPI) following maximal treadmill exercise and pharmacologic coronary vasodilation with intravenous dipyridamole (DP) was performed in 33 patients. Thallium201 imaging defects in six myocardial perfusion regions were correlated with stenoses in their respective vascular distributions.

Role of programmed stimulation in assessing vulnerability to ventricular arrhythmias.

Programmed electrical stimulation can now be safely performed in humans for the evaluation of therapy for recurrent ventricular tachyarrhythmia. Such studies may also eventually be found useful in predicting the risk of developing life-threatening ventricular tachyarrhythmias. The repetitive ventricular response phenomenon has been evaluated.

Termination of ventricular tachycardia with ventricular stimulation: salutary effect of increased current strength.

The effect of increased stimulus current strength on the right ventricular effective refractory period during sustained ventricular tachycardia and on the ability of single premature right ventricular stimuli to terminate ventricular tachycardia was evaluated. Studies were performed during 53 episodes of sustained ventricular tachycardia in 25 patients. Forty-four of 53 episodes were slowed by pharmacologic therapy.

Role of catheter mapping in the preoperative evaluation of ventricular tachycardia.

Although surgery is an accepted mode of therapy for refractory ventricular tachycardia, routine aneurysmectomy has yielded unpredictable results. This is believed to have occurred because there was no documentation that the arrhythmia actually arose from resected aneurysmal tissue. Catheter endocardial mapping has been used to localize preoperatively the area of origin of the arrhythmia.

Intravenous dipyridamole combined with isometric handgrip for near maximal acute increase in coronary flow in patients with coronary artery disease.

Twenty-four patients with coronary artery disease were studied during cardiac catheterization to determine the effects of sustained isometric handgrip exercise and intravenous dipyridamole and their combination on coronary and systemic hemodynamics and measured coronary luminal caliber. During 4 to 5 minutes of 25 percent maximal handgrip, blood pressure and heart rate increased 24 and 19 percent, respectively, coronary sinus flow increased to 1.7 x baseline value, and epicardial coronary arteries constricted to increase predicted flow resistance by 40 percent in 36 diseased arterial segments.

Anatomic and electrophysiologic correlates of ventricular tachycardia requiring left ventricular stimulation.

In 108 patients with reproducible initiation of ventricular tachycardia by programmed ventricular stimulation, the ventricular tachycardia was initiated only by left ventricular stimulation in 12 (11 percent). Programmed ventricular stimulation included single and double extrastimuli extrastimuli at three cycle lengths and bursts of rapid pacing to cycle lengths of 250 ms. Clinical, electrocardiographic, angiographic, hemodynamic and electrophysiologic data were available in 74 of 96 patients with ventricular tachycardia initiated by right ventricular stimulation (Group A) and in all 12 patients with ventricular tachycardia initiated only by left ventricular stimulation (Group B).