PubMed Health⌕ Search

Biomedical subjects

B Avitall

Publications and source records attributed to B Avitall.

42 records · Page 3Linked to original sources
PubMed1977

Dispersion of effective refractory period during abrupt reperfusion of ischemic myocardium in dogs.

Dispersion of the effective refractory period was measured in anesthetized dogs using a computerized system and bipolar epicardial electrodes or, alternatively, transmural plunge electrodes. Measurements were made at 1 minute intervals during short (5 minute) and long (15 minute) periods of coronary arterial ligation and for 3 to 5 minutes after release of the ligatures. Both transepicardial and transmural temporal dispersion of refractoriness correlated well with the increased vulnerability to spontaneous ventricular fibrillation during short periods of ligation and the relative electrical stability observed toward the end of the longer periods of ligation. During reperfusion, transmural dispersion increased somewhat after ligature release in the longer-term experiments but the increase did not appear adequate to explain the associated large incidence of spontaneous arrhythmias after release. Effective refractory periods measured at one nonischemic and five ischemic electrode sites at intervals as short as 20 seconds revealed abrupt shortening of the refractory period at all ischemic sites during the 1st minute of reperfusion, resulting in a large but short-lived electrical gradient between the ischemic and nonischemic myocardium. This increased dispersion between the ischemic and nonischemic myocardium occurred at a time of maximal vulnerability to reperfusion arrhythmias. However, this increased dispersion was greater after the 5 minute than after the 15 minute periods of ligation and thus does not fully explain the greater incidence of reperfusion arrhythmias after ligature release in the longer-term studies. Although arrhythmias of acute ischemia are associated with increased dispersion of refractoriness within theischemic segment and reperfusion arrhythmias with dispersion between ischemic and nonischemic segments, other electrophysiologic alterations probably play an important role in the genesis of the arrhythmias of reperfusion.

Animals↗
PubMedDate not supplied

Heterotopic heart transplantation: electrophysiologic changes during acute rejection.

To identify electrophysiologic (EP) measurements sensitive to heart transplant rejection, heterotopic thoracic heart transplantation was performed in 11 dogs. Endocardial biopsies were performed daily for up to 9 days, and the severity of rejection was classified as mild, moderate, or severe. Late diastolic thresholds; refractory periods of the left ventricle and right atrium; and conduction times from the right atrium to left atrium, left ventricle to right ventricle, and right atrium to right ventricle were measured daily in transplanted and recipient hearts. The amplitude of the left atrium and right ventricular electrograms was recorded daily. In the recipient hearts no significant EP changes were observed after the second postoperative day. Left ventricular and right atrial refractory periods in both hearts did not change. In the transplanted hearts the conduction times of the right and left atria (but not the conduction time of the left to right ventricles) and right atrium to right ventricle identified moderate rejection; right atrial diastolic threshold was a marker only for severe rejection. Amplitudes of the left atrial and right ventricular electrograms decrease significantly only with severe rejection. At postmortem histologic evidence for rejection was greater in the atria than the ventricles. EP changes in the atria and atrioventricular conduction are more sensitive indicators of acute rejection than ventricular EP changes and correlate with the histologic grade of rejection. None of the measurements evaluated, however, was shown to be a sensitive marker of mild rejection.

Acute Disease↗
PubMedDate not supplied

Rationale, development, and clinical outcomes of a multidisciplinary amiodarone clinic.

OBJECTIVES: To review the rationale and development of a multidisciplinary amiodarone clinic, and document the clinical outcomes resulting from its implementation. METHODS: A clinic was established to provide an ambulatory setting in which patients receiving amiodarone could be followed according to published guidelines by a multidisciplinary team of cardiovascular health care specialists. Patients receiving amiodarone were referred to the clinic by their primary physicians. A data base containing each patient's medical history, current drug therapy, and baseline laboratory values was developed during the initial visit. Liver function tests, thyroid function tests, and chest radiographs were performed every 6 months, and pulmonary function tests were scheduled on an annual basis. Dosage adjustments were performed in select patients. RESULTS: Since November 1996, 60 patients have been referred to the amiodarone clinic. Mean length of follow-up before and after referral was 16.3+/-25.5 and 9.2+/-5.5 months, respectively. Laboratory tests were performed according to accepted guidelines in 14 (23%) patients before referral compared with 54 (90%) patients after enrollment (p<0.001). Previously unrecognized adverse events were detected in 21 (35%) patients, including pulmonary fibrosis, QT prolongation, liver enzyme elevation, hypothyroidism, hyperthyroidism, and asthma exacerbation. Amiodarone was discontinued in six patients, four of whom had suspected pulmonary toxicity. The dose of amiodarone was adjusted in 29 (48.4%) patients. CONCLUSION: Many patients receiving amiodarone are not being followed according to published recommendations. Implementation of a specialized, multidisciplinary amiodarone clinic improves outcomes by monitoring for early detection of drug-related toxicities and by facilitating proper dosage modifications.

Adult↗