Search

Objectives. We investigated the patterns of perfusion and metabolism in dysfunctional myocardium whose contractility improved with dobutamine.Background. Clinical studies have suggested that dobutamine echocardiography can identify hibernating myocardium, but laboratory studies suggest that reduced perfusion limits the response to dobutamine.Methods. Twenty-five patients with coronary disease and ventricular dysfunction underwent low (5 and 10 μg/kg body weight per min) and high dose (maximum of 50 μg/kg per min) dobutamine echocardiography and positron emission tomography (PET) using nitrogen-13 (N-13) ammonia and fluorine-18 fluorodeoxyglucose (FDG) for imaging of perfusion and metabolism. Wall motion and tracer uptake were scored in 16 left ventricular segments.Results. Perfusion and metabolism were normal in 56.4%, mildly reduced in 29.1% and mismatched (reduced perfusion, preserved FDG uptake) in 14.5% of dysfunctional segments viable on PET. Wall motion improved with dobutamine in 89 dysfunctional segments (62 at low dose, 27 only at peak dose), and 86 of these (97%) were viable on PET. Improvement in wall motion with dobutamine was more common in segments with normal perfusion and metabolism (56.5%) than in those with mildly reduced tracer uptake (28.5%, p < 0.001) and those with mismatch (32%, p = 0.03). All the segments with a biphasic response were supplied by vessels with ≥70% stenosis, and 88% had normal perfusion and metabolism.Conclusions. The majority of viable segments with rest dysfunction had normal perfusion and metabolism, suggesting that myocardial stunning was common. Improvement of wall motion at low and high doses of dobutamine was highly correlated with myocardial viability on PET and was more common in myocardium with normal perfusion. A biphasic response to dobutamine identified segments with normal perfusion and metabolism supplied by severely diseased vessels.(J Am Coll Cardiol 1997;29:55–61)>

Objectives. This study attempted to determine the safety and accuracy of dobutamine stress echocardiograpby for detection of coronary artery disease in patients with dilated cardiomyopathy. Background. Detection of regional wall motion abnormalities at rest does not reliably distinguish ischemic front nonischemic cardiomyopathy. Previous studies have shown that dobutamine stress echocardiography safely and accurately identifies coronary artery disease in patients without dilated cardiomyopathy. Methods. Seventy patients with dilated cardiomyopathy under-went dobutamine stress echocardiography. Echocardiograms were obtained at baseline and at low (5 to 10 μg/kg body weight per min) and peak doses of dobutamine. Rest and stress left ventricular wall motion scores were derived from analysis of regional wall motion. Fifty-four subjects underwent coronary angiography. Results. Dobutamine infusion was terminated after achievement of the target heart rate or maximal protocol dose in 49 patients (70%), ischemia in 12 (17%), arrhythmia in 4 (6%) and side efects in 5 (7%). No patient had prolonged ischemia or sustained arrhythmia. Of those with angiographic studies, 40 had significant coronary artery disease (≥50% diameter stenosis). Use of the change in global wall motion score index from low to peak dose resulted in a sensitivity of 83% for dobutamine stress echocardiography and a specificity of 71% for detection of coronary artery disease. Sensitivity for detection of triple-,double-and single-vessel disease was 100%, 83% and 69%, respectively. Conclusions. Dobutamine stress echocardiography safely provides diagnostic information in patients with dilated cardiomyopathy. This technique has high sensitivity for multivessel coronary artery disease but only moderate specificity.

BackgroundRadiofrequency catheter ablation is standard treatment for children with re-entrant supraventricular tachycardias. Autonomic changes have been noted after such ablation for atrioventricular nodal re-entry tachycardia, but not as well documented with atrioventricular re-entry over an accessory pathway.Methods and resultsIn 10 normal paediatric volunteers and 12 children referred for electrophysiologic testing and radiofrequency ablation of supraventricular tachycardia, non-invasive autonomic function tests and tilt-table testing were performed, and the variability in 24-h heart rate was analysed. Patients with supraventricular tachycardia underwent these tests both 24–72 h before and 24 h after ablation. Patients with tachycardia underwent additional autonomic testing to assess the sensitivity of baroreceptors and the intrinsic heart rate with autonomic blockade immediately before and after ablation. One non-invasive autonomic function test, namely handgrip, demonstrated significant differences (p < 0.05) in diastolic blood pressure before and after ablation, though these values did not differ from controls. Significant decreases were noted in two indexes of the variability of heart rate before and after ablation (p < 0.05). Certain tilt test variables also demonstrated significant differences between controls and those with tachycardia subsequent to ablation. Intracardiac testing demonstrated changes (p < 0.05) in sinus cycle lengths, effective refractory periods and/or blood pressures at baseline and during testing of the sensitivity of baroreceptors before and after ablation. These changes were consistent with increased sympathetic or decreased parasympathetic tone. With autonomic blockade, these differences were abolished.ConclusionsCatheter ablation of accessory pathways in children was associated with changes consistent with increased sympathetic or decreased parasympathetic tone. These autonomic changes persisted 24 h after the ablation procedure.

Ventricular tachycardia induced by programmed electrical stimulation during amiodarone therapy often does not preclude a good clinical response. The purpose of this study was to determine whether use of discriminant analysis could distinguish patients who remained asymptomatic from those who subsequently developed symptomatic ventricular tachycardia or cardiac arrest. Studies were performed in 37 patients with sustained ventricular tachycardia who still had ventricular tachycardia induced during programmed electrical stimulation during amiodarone therapy. The mean follow-up time was 14.1 ± 1.3 months (± SEM). Twenty-three patients remained asymptomatic, whereas 14 patients had symptomatic recurrence of their ventricular tachycardia.In patients with recurrence of arrhythmia compared with asymptomatic patients, administration of amiodarone caused a longer ventricular effective refractory period (296 ± 8 versus 271 ± 7 ms, p < 0.05) and a greater change in corrected QT [QTc] interval (90 ± 18 versus 44 ± 9 ms, p < 0.02), but no difference in the decrease in premature ventricular complexes after treatment with amiodarone. During amiodarone therapy, nonbundle branch reentrant repetitive ventricular responses were induced by a single ventricular extrastimulus during sinus rhythm in 9 of 14 patients with recurrent arrhythmias compared with 2 of 21 asymptomatic patients (p = 0.001). Also, less aggressive pacing techniques were required to induce ventricular tachycardia in 9 of 14 symptomatic patients compared with 4 of 23 asymptomatic patients (p < 0.02). A discriminant analysis using the presence of nonbundle branch reentrant repetitive ventricular responses, change in method of ventricular tachycardia induction and either the change in QTcinterval or ventricular effective refractory period correctly identified clinical outcome in 90% of the patients, and all patients with recurrent arrhythmias were classified correctly. It is concluded that electrophysiologic testing during amiodarone therapy can provide data that identify patients who appear to be at risk for development of ventricular tachycardia after hospital discharge.

Antiarrhythmic therapy in 506 consecutive patients undergoing 1,268 antiarrhythmic drug trials for ventricular tachycardia or ventricular fibrillation was reviewed for evidence of arrhythmogenic drug effect defined as the occurrence of a new form of ventricular tachyarrhythmia temporally associated with initiation of drug therapy or dosage increase. Arrhythmogenic effects occurred in 6.9% of patients and 3.4% of drug trials. This ranged from a high of 11.8% caused by encainide to none occurring with procainamide, tocainide or beta-adrenergic blocking drugs. The incidence of arrhythmogenesis was significantly greater in patients whose presenting arrhythmia was sustained ventricular tachycardia than it was in those who presented with nonsustained ventricular tachycardia or ventricular fibrillation (p = 0.02). Decreased systolic function measured echocardiographically at the base of the left ventricle was associated with an increased incidence of arrhythmogenic effects (p = 0.006) whereas global left ventricular ejection fraction was not. Age, gender, cardiac diagnosis, location of prior myocardial infarction and New York Heart Association functional class for heart failure were not related to the occurrence of drug-induced arrhythmias. These findings emphasize the need for in-hospital cardiac monitoring during initiation of antiarrhythmic drug therapy for ventricular tachyarrhythmias.

Objectives.This study sought to evaluate the delivery efficiency, intramural retention and antirestenotic efficacy of soluble colchicine or a colchicine analogue delivered into the arterial wall after angioplasty as well as the efficacy of these medications after prolonged local release from biodegradable microparticles.Background.Local delivery of pharmacologic agents is a potential treatment for restenosis. However, the delivery efficiency of the technique and the choice of agent to modulate cellular proliferation are unknown. It was hypothesized that restenosis would be unaffected by colchicine or a hydrophobic colchicine analogue with short intramural retention, whereas it would be reduced after prolonged local release.Methods.Rabbit atherosclerotic femoral arteries underwent angioplasty followed by local delivery. Delivery efficiency and intramural retention of 3H-colchicine were evaluated. The effect of agents in soluble formulation or released from microparticles on angiographic and morphometric restenosis was evaluated at 2 weeks and compared with that in the control groups (angioplasty only and local infusion of carrier solution).Results.Delivery efficiency was 0.01% and intramural retention

Transthoracic echocardiographic examination of the proximal left coronary system was performed in 59 patients who had dilated cardiomyopathy to determine if this technique could distinguish between ischemic and nonischemic dilated cardiomyopathy. With use of annular array transducers (3.5 or 5 MHz) and digital image processing, echocardiographic visualization of the coronary arteries was successful in 55 (93%) of 59 patients. As assessed by coronary angiography, 32 subjects had ischemic cardiomyopathy and 27 had nonischemic cardiomyopathy.Twenty-seven (84%) of the 32 patients who had coronary artery disease and 24 (89%) of the 27 patients with nonischemic cardiomyopathy were correctly identified. The accuracy of coronary echocardiography was 86% in the entire study group and 93% when patients with inadequate studies were excluded. All subjects who had ischemic cardiomyopathy had evidence of disease by coronary echocardiography or segmental wall motion abnormalities. Multivariate analysis permitted correct classification of 93% of all subjects based on the results of the coronary echocardiogram, evaluation of segmental wall motion and a history of prior myocardial infarction. The correct diagnosis was made in 86% when the results of coronary echocardiography were excluded from analysis using all other echocardiographic and clinical variables.Transthoracic coronary echocardiography can be performed with a high degree of success in patients with dilated ventricles and the technique can reliably distinguish between ischemic and nonischemic dilated cardiomyopathy.

The utility of exercise echocardiography for the diagnosis of coronary artery disease has been demonstrated in populations consisting largely of men with a high prevalence of disease. To determine the diagnostic value of exercise echocardiography in women, 57 women who presented with chest pain were studied with coronary cineangiography and echocardiography combined with either treadmill (n = 38) or bicycle exercise (n = 19). Significant coronary artery disease (greater than or equal to 50% reduction in luminal diameter) was present in 28 (49%) of 57 patients, including 16 (84%) of 19 who had typical angina, and 12 (32%) of 38 who had atypical chest pain. The overall sensitivity and specificity of echocardiography were both 86%. Exercise echocardiography correctly determined the presence or absence of coronary artery disease in 32 (84%) of 38 patients who had atypical chest pain and in 17 (89%) of 19 who had typical angina (p = NS). The exercise electrocardiogram (ECG) was nondiagnostic in 17 patients (30%) who had rest ST segment depression or ST depression with exercise that could also be induced by hyperventilation or changes in position. The correct diagnosis was made by echocardiography in 14 (82%) of 17 patients with a nondiagnostic exercise ECG. In conclusion, exercise echocardiography has a clinically useful level of sensitivity and specificity for the detection of coronary artery disease in women. The technique provides diagnostic information in women presenting with atypical chest pain and in those who have a nondiagnostic exercise ECG.