ABSTRACTS

PAROXYSMAL A-V NODAL HEENTRANT TACllYCARDIA FOLLClk'NG ATROPINE Masood Akhtar, ?m, Anthony N. Dannto, ~JJ, William Bats-

ford, MD, Anthony N. Caracta, ?ID, leremy N. Ruskin, Ml), Sun H. Lau, MD, U.S. Public Health Service Hospital, Staten Island, E:ew York

It is well known that a crlticnl ;,-V nodal conduction delay is required for the initiation of paroxysmal A-V nodal reentrant txhycardin (PAT). This critical A-V nodal delay can be achieved by appropriately timed pre- mature atria1 beats occurring within the relative re- fractory period of the A-V node or during A-V nodal Wenckebach cycles produced by rapi< atria1 pi:cing. I!<ing His bundle recordings and premature atrial stimalation techniques four patients (pts) were studied before and after small doses (0.5 mg ‘I.V.) of atropine, at cornpar- able preceding atria1 cycle lengths (AI-Al) and atria1 premature coupling intervals (AL-AZ), up to the point oi atria1 refractoriness. Before atropine, 3 pts demon- strated single atria1 echo beats and 1 pt had no atria1 echo beats. After atropine, sustained PAT occurred in all 4 pts. In 3 pts, PAT occurred at the same A-V nodal delay which before atropine produced only single echo beats and in the 4th pt, atropine permitted the attain- ment of a greater and requisite A-V nodal for PAT. PAT due to A-V nodal reentry could be distinguished from sinus tachycardia and sinus node reentrant tachycardia. It is postulated that atropine which shortens the effect- ive and functional refractory periods of.the A-V node and shortens antegrade and retrograde A-V nodal con- duction time caused a critical and necessary balance between conduction within the antegrade and retrograde limbs of the reentrant circuit so that PAT could be sustained.

EVALUATION OF THE EFFECTS OF ANTITHROMBOTIC THERAPY ON

SURVIVAL FOLLOWING AORTOCORONARY BYPASS SURGERY

Mahdi S. Al-Bassam, MO; Robert J. Hall, MO, FACC; Efrain

Garcia, MO, FACC; Robert 0. Leachman, MD, FACC; Louis L.

Leatherman, MD; Grady L. Hallman, MO, FACC; Oenton A.

Cooley, MD, FACC; Texas Heart Institute, St. Luke’s

Episcopal Hospital, Houston, Texas

Various antithrombotic regimes used emperically by vari-

ous consulting Cardiology Sections of this Institute were

evaluated 6 to 40 months postoperatively to determine ef-

fects on late survival (after I month). Coumadin (C) was

favored in the early period while Persantine (P) and as-

pirin (A) were used alone or in combination, more fre-

quently in the last 2 years. Therapeutic regimes were

continued for a sufficient period assuring comparable

patient enlistment into each therapeutic group. Charts,

letters to patients and information from private doctors

were reviewed to collect data on C, P, & A regimes. Of

the 1404 patients operated at this Institute from August

1969 to September 1972, adequate follow-up drug data were

available on 1078 patients, 60 of whom died in the fol-

low-up period. The “life survival curve” (Cutler) of the

1078 subgroup was closely similar to the curve for the

total series of 1404 patients. Therapy prescribed, sing-

ly or in combination, was as follows: C, 557 patients;

P, 430; A, 358; and no C, P, A, 243.

Follow-up C P

6 mo. 99. I% 99.

18 mo. 95.6% 96.6% 30 mo. 93.1% 94.2% 96.2% 89.0% 92.2%

All percentages are related to cumulative survivals.

Higher survival was associated with A alone or in any com-

bination while C and P were close to the average rate of

attrition. No antithrombotic therapy was associated with

a decreased survival in the observed group.

DOSE-RESPONSE EFFECTIVENESS OF PROPRANOLOL FOR THE TREATMENT OF ANGINA PECTORIS Edwin L. Alderman, M.D., F.A.C.C., Mario Lopes, M.D., Donald C. Harrison, M.D., F.A.C.C., Cardiology Division, Stanford University School of Medicine, Stanford CA

A clinical trial of 10 months duration in 17 patients(pts) evaluated the response of angina to propranolol in 4 divided daily doses of placebo, 20, 40 and 80 mg, in rela- tion to drug blood levels. Pts entered the double-blind portion of the study only after the frequency of angina1 episodes was greater than 5/week during a 3 month period of single-blind placebo medication. Pts then entered 4 6-week double-blind periods, receiving each of the 4 dose levels in a random sequence. Angina frequency and nitro- glycerin consumption were recorded by pts on personal diaries collected biweekly. Average exertional angina episodes per week were reduced from 8.222.4 during placebo medication to 5.251.0 (N.S.) while taking 80 mg/day, 4.8 +1.3 (pcO.5) while taking 160 mg/day, and 3.3~1.2(p<.Ol) while taking 360 mg/day. Physician evaluations at bi- weekly intervals and exercise testing during each dose period confirmed the statistical significance of the clinical response. Mild adverse effects were noted in 8 of the 17 pts and in some pts rebound withdrawal symptoms from propranolol occurred. Propranolol blood levels ob- tained between 100 and 180 minutes after the last tablet correlated highly with the dose and the clinical response. Propranolol doses of 80 mg/day were clinically ineffective and generally achieved blood levels below 30 ng/ml,whereas daily doses of 160 and 320 mg achieved blood levels above 40 ng/ml and were effective in reducing angina frequency and nitroglycerin consumption, and in increasing pain-free days and treadmill exercise tolerance.

ENDOMYOCARDIAL BIOPSY: ITS CLINICAL APPLICATION. Ali, N. Ferrans, V.J., Banks, T., and Roberts, W.C. D. C. General Hospital and National Heart & Lung Insti- tute, Bethesda, Maryland.

Fifty patients (pts) with (c) suspected cardiomyopathy (CM) in the presence or absence of a systemic disease were selected for endomyocardial biopsy in an attempt to clarify the etiology of the CM. The primary diagnoses included myocarditis (viral), bacterial endocarditis, sarcoidosis, sickle cell disease, eosinophilic leukemia, systemic sclerosis, myxedema, throtoxicosis and chronic alcoholism. Three techniques were used i.e. Konno's Bioptome in 25 pts, GFB biopsy catheter either alone in 20 or introduced through an end hole catheter in 5. Two to 5 specimens were obtained. Overall success rate was 92%. Complications included ventricular tachycardia (TV) in a pt c sarcoidosis and recurrent VT, ST-T changes in 1 pt and right bundle branch block in 4. All the changes were transient. No other immediate or late complications secondary to the procedure were noted. The structural changes observed were: interstitial fibrosis, cellular hypertrophy and degenerative changes of edema, lipid deposition, myofibrillar loss, sarco- plasmic reticular dilatation & mitochondrial damage. The degree and extent of these changes correlated c the duration and severity of heart disease. No viral particles but nuclear & nucleolar alterations were found in 2 pts from whom Coxsackie B viruses were isolated. Tuboreticular structures were for,nd in a thyrotoxic pt. Alcoholic & non-alcoholic pts c CM could not be distin- guished morphologically.

122 January 1974 The American Journal of CARDIOLOGY Volume 33