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D L Kuchar

Publications and source records attributed to D L Kuchar.

26 records · Page 2Linked to original sources
PubMed1986

Signal-averaged electrocardiogram for evaluation of recurrent syncope.

Signal-averaged electrocardiography (ECG) was performed in 150 consecutive patients presenting with syncope, to determine its diagnostic role in identifying patients with ventricular tachycardia (VT) and in determining their long-term prognosis. Patients also underwent a standardized investigational protocol to independently determine a cause of syncope. Twenty-nine patients had a late potential, 107 had a normal signal-averaged electrocardiogram and 14 had bundle branch block on 12-lead ECG. Signal-averaged ECG identified a late potential in 16 of 22 patients with VT and was normal in 101 of 114 patients in whom syncope was attributed to causes other than VT or remained unexplained (sensitivity 73%, specificity 89%, predictive accuracy 55%). In patients with coronary artery disease, the predictive accuracy increased to 82%. Absence of a late potential identified a group of patients with a very low incidence of VT. During follow-up of 1 to 20 months (median 11), 15 patients (10%) died, 6 suddenly. There was no significant difference in survival or recurrence of syncope between patients with and without a late potential. Signal-averaged ECG can noninvasively identify patients with serious ventricular arrhythmias among an unselected group presenting with syncope.

Adolescent↗
PubMed1986

The prevalence of arrhythmias in hypertrophic cardiomyopathy: role of ambulatory monitoring and signal-averaged electrocardiography.

Hypertrophic cardiomyopathy (HCM) is associated with a high incidence of supraventricular and ventricular arrhythmias. The presence of ventricular tachycardia (VT) in patients with HCM has been associated with a high risk of sudden death. Forty-seven patients with HCM (31 male, 16 female, mean age 47 years) underwent continuous 24-hour ambulatory electrocardiographic (ECG) monitoring. High grade ventricular arrhythmias (modified Lown class 3, 4a, 4b) were found in 20 patients (43%) with VT in 11 (24%). In each case the arrhythmia was asymptomatic. Supraventricular arrhythmias were detected in 16 patients (34%). Signal-averaged electrocardiography in 27 patients showed late potentials in three of 11 patients with repetitive ventricular arrhythmias and was negative in 15 of 16 patients without these arrhythmias. In conclusion, asymptomatic high grade ventricular and supraventricular arrhythmias are common in HCM and are readily detected with continuous electrocardiographic monitoring. Signal-averaged ECG has low sensitivity for the detection of subclinical VT in patients with HCM.

Adolescent↗
PubMed1986

High-frequency analysis of the surface electrocardiograms of patients with supraventricular tachycardia: accurate identification of atrial activation and determination of the mechanism of tachycardia.

Signal processing of the electrocardiogram (ECG) was performed during supraventricular tachycardia (SVT) in 24 patients in an attempt to locate the P wave and to characterize its morphology in three orthogonal planes. In patients with atrioventricular reciprocating tachycardia, a discrete atrial signal could be identified within the ST segment and/or T wave with inferior-to-superior orientation. Atrial activation was identified in patients with primary atrial tachycardia as long as there was a constant relationship between each QRS complex and the preceding atrial signal. Patients with atrioventricular nodal reentrant tachycardia were deduced to have simultaneous atrial and ventricular activation when no atrial signal could be seen elsewhere in the cycle. Mean maximum P wave amplitude was 25.4 +/- 6.3 microV during SVT, with a mean noise level below 1.0 microV. Signal processing of the ECG during SVT enhances the detection of the P wave and the appreciation of P wave morphology, both of which are important factors in the noninvasive determination of the electrophysiologic mechanisms of SVT.

Atrial Flutter↗
PubMed1986

Late potentials detected after myocardial infarction: natural history and prognostic significance.

The risk of developing spontaneous ventricular tachycardia (VT) and/or sudden death ("arrhythmic events") was prospectively assessed in 165 patients who survived acute myocardial infarction. Signal-averaged electrocardiograms (ECGs) were performed before hospital discharge and then serially at regular intervals over the following year. In addition, 24 hr Holter monitoring was performed and left ventricular ejection fraction was determined. Sixty-five patients (group 1) had abnormal signal-averaged ECGs (voltage in the last 40 msec of the filtered QRS less than 20 microV or filtered QRS duration greater than 120 msec), 92 had normal signal-averaged ECGs (group 2), and eight had bundle branch block (excluded from analysis). In group 1, spontaneous normalization of the voltage in the last 40 msec of the QRS complex occurred in 30% of patients after 12 months, although total filtered QRS duration did not change overall. During follow-up of up to 20 months (median 11), seven patients died suddenly and six presented again with spontaneous, symptomatic VT. Eleven of 65 (17%) group 1 patients had an arrhythmic event compared with one of 92 patients (1%) in group 2 (p less than .001). The sensitivity of the signal-averaged ECG as a predictor of arrhythmic events was 92% with a specificity of 62%. Patients with subsequent arrhythmic events had considerably lower voltage in the last 40 msec of the QRS (11.0 +/- 8.3 vs 32.0 +/- 21.9 microV; p less than .001) than those without such events, and longer filtered QRS complexes (121 +/- 14 vs 105 +/- 12 msec; p less than .001). Multivariate logistic regression determined that the signal-averaged ECG provided independent prognostic information from the presence of complex ventricular ectopy and the degree of left ventricular dysfunction assessed at the time of hospital discharge. Signal-averaged ECGs provide important prognostic information in identifying patients at risk of arrhythmic events after myocardial infarction. Dynamic changes in the terminal QRS voltage are observed during the first year after myocardial infarction.

Death, Sudden↗
PubMed1985

High dose furosemide in refractory cardiac failure.

High dose furosemide is commonly used in renal failure to induce diuresis but rarely employed in cardiac failure. As furosemide elimination depends largely on renal excretion, drug accumulation with attendant side-effects would be expected to occur more commonly with renal failure than with cardiac failure. Response to a combination of thiazide diuretics and lower doses of furosemide is often unpredictable, ineffective and sometimes hazardous. High dose furosemide (greater than or equal to 0.5 g day-1) was administered for at least four weeks in 24 patients with severe cardiac failure refractory to a lower dose and to other conventional therapy. Mean maintenance dose of furosemide was 0.7 g day-1 and the maximum dose of furosemide averaged 1.3 g day-1. A peak dose of 8 g day-1 was used successfully in one patient. Improvement was observed in all patients when dosage was increased to and above 0.5 g day-1. There were no major side-effects although new-onset gout (4) and tinnitus (1) were reported; hypokalaemia was readily controlled with spironolactone or potassium supplements. Average duration of therapy was 12 months with a maximum of 33 months. High dose furosemide is logical and effective therapy (with other measures) for severe cardiac failure and relatively safe when administered cautiously. The maximum safe dose is probably no less than that used in renal failure.

Blood Pressure↗
PubMed1985

Pacemaker reversion for suspected supraventricular tachycardia.

Overdrive atrial pacing was employed in twelve patients with suspected supraventricular tachycardia resistant to drug therapy. Eleven of these patients reverted to sinus rhythm with pacing either immediately or after a short episode of atrial fibrillation. In one patient, recordings from the atrial electrode indicated that a broad complex tachycardia was of ventricular rather than supraventricular origin. No complications were encountered and the procedure was well tolerated in all. Overdrive pacing is suggested as a safe alternative to DC cardioversion in drug-resistant supraventricular tachycardia, particularly in the presence of digitalis, in the elderly and in patients with chronic lung disease.

Adult↗
PubMed1985

The role of signal averaged electrocardiography in the investigation of unselected patients with syncope.

The cause of syncope is often not determined, despite extensive investigations, yet it is important to identify the high risk group who may be in danger of sudden death due to ventricular arrhythmias. Recent studies have shown that the signal averaged electrocardiogram (SA ECG) can identify low amplitude signals in the terminal portion of the QRS and ST segment (late potentials) recorded from the body surface, which represent areas of delayed conduction in small areas of diseased myocardium in patients with ventricular tachycardia (VT). Sixty-five consecutive patients presenting to hospital with syncope were prospectively evaluated to determine a cause of syncope; this included quantitative analysis of the terminal QRS complex using SA ECG. A cardiac cause of syncope was assigned to 49% of patients, a non-cardiac cause to 20%, and no cause was found in the remaining 31%. Initial history and physical examination established a diagnosis in 14% of patients. A prior history of heart disease was an important indicator to a cardiac cause for syncope. Continuous electrocardiographic monitoring was diagnostic in 23% and the yield for electrophysiological testing (in a selected subgroup) was 40%. Ancillary cardiac and neurological investigations were of little diagnostic value, although they were useful in defining the severity and extent of clinically suspected conditions. SA ECG identified a late potential in 11 of 13 patients with VT, but was normal in all except three of the remaining patients who were not considered to have VT (sensitivity 85%, specificity 94%). We conclude that high frequency analysis of the signal averaged ECG is a reliable non-invasive indicator of syncope due to VT.

Adolescent↗