ABSTRACTS

left ventriculography, coronary blood flow, myocardial lactate extraction, and coronary sinus : arterial creatine phosphokinase (CPK) gradients were studied immedi- ately before surgery. Coronary arteriography demon- strated 3-vessel obstruction (>50%) in 11 of 15. Cor- onary blood ilow, using a constant antipyrine infusion method, showed abnormally low values, averaging 78 cc/100 g per min 4 21 (normal 92-120). Myocardial lac- tate production was observed in 13 of 15. Lactate pro- duction occurred at rest in 3 and during controlled tachycardia (lOO-120imin) in 10. A coronary sinus : ar- terial CPK gradient was observed in all cases. Two to 7 days after surgery, restudy showed coronary blood flow to increase from 78 to 135 cc/100 g per min (P <O.Ol). Myocardial lactate extraction was normal in all cases (mean 28.9%) despite controlled tachycardia at 140/min. Clinical observations (2 weeks-7 months) in the 13 survivors showed these patients to be free of coronary pain, arrhythmia or heart failure. This study suggests that early surgical intervention with coro- nary revascularization, when myocardial infarction is clinically progressive, may be effective in reducing mortality and morbidity by limiting the extent of in- farction.

Indirect Assessment of Coronary Artery Bypass Grafts

JAMES T. WILLERSON, MD*; ELDRED D. MUNDTH, MD; ROBERT E. DINSMORE, MD; H. WALKER; MORTIMER J. BUCKLEY, MD; W. GERALD AUSTEN, MD, FACC; GORDON S. MYERS, MD, FACC; C. A. SANDERS, MD, Boston, Massachusetts

Fifty-seven patients (mean age 50 2 1.4 SE) were studied before and after coronary artery bypass graft surgery (CABG) utilizing indirect techniques. Fifty had at least 1 myocardial infarction preoperatively. Phonocardiograms, carotid arterial tracings, apex car- diograms and electrocardiograms were obtained pre- operatively in all and 2 weeks after CABG (49) and 2 to 4 months after CABG (32). Cardiac catheterization and angiographic studies demonstrated significant (>70% narrowing) 3-vessel coronary artery disease (CAD) in 13, 2-vessel CAD in 35 and l-vessel CAD in 9. There was generalized reduction in left ventricular (LV) contractility in 8 and marked reduction in 1 or more localized areas in 36. Only 1 patient preoperatively had significant mitral regurgitation (MR) .

Fourth heart sounds (S4’s) were present preopera- tively in 56, 2 weeks after CABG in 47 of 49 studied (no significant difference, NS), and 2 to 4 months after CABG in 31 of 32 studied (NS). Third heart sounds (S3’s) were present in 30 preoperatively, in 30 of 49 2 weeks post-CABG (NS), and in 20 of 32 at 2-4 months (NS). In 9 new S3’s developed 2 weeks after CABG but in 9 the pre-CABG S3’s disappeared. Before CABG, 10 had systolic murmurs compatible with but not specific for MR, 2 had paradoxically split second heart sounds (Sz’sj at rest, and 37 had early systolic sounds suggesting early clicks or split first heart sounds. There was no significant change in the inci- dence of systolic murmurs, splitting of S2’s or early systolic sounds after CABG.

These studies demonstrate the following: (1) CABG’s do not in the relatively early postoperative period completely reverse areas of reduced LV compli- ance which are responsible for the genesis of S4’s; (2)

the influence of CABG is more variable regarding pres- ence or absence of S3’s, but a few patients acquire new S3’s in the early post-BABG period; and (3) early sys- tolic sounds are relatively common in patients with CAD, whereas paradoxical splitting of S2’s are uncom- mon at rest. Neither changed significantly after CABG.

Protective Zone for Ventricular Fibrillation

MARSHALL WOLF, MD*; EDUARDO SEROPPIAN, MD, FACC; BERNARD LOWN, MD, FACC; JOHN TEMTE, MD, PhD; ARTHUR GARFEIN, MSEE; R. VERRIER, PhD, Boston, Massachusetts

The ventricular vulnerable period (VP) is a 20 to 40 msec interval during ventricular repolarization when a 0.5 to 1.0 watt set discharge (S,) can precipitate ven- tricular fibrillation (VF). Termination of VF even if attempted within seconds requires large energies (50- 100 watt set). We have observed that VF produced by S1 is prevented if a second 0.5-1.0 watt set pulse (S,) , is coupled to S1. To be effective, S, must be delivered within a critical interval of time following Si, which we define as the protective zone (PZ) . S2 is ineffective in preventing VF if delivered before or after the PZ. This PZ has been observed in each of 30 mongrel dogs with both transthoracic (underdamped capacitor) and endocardial (right ventricular unipolar square wave) discharges. The PZ begins 10 to 40 msec after the end of the VP and has a duration of 25 to 90 msec. The duration of the PZ varies inversely with heart rate (60 to 300 beats/min). For a given heart rate, the time of onset of the PZ (inner boundary) is fixed in the cardiac cycle and is independent of the location of S, in the VP. In contrast, the outer boundary of the PZ main- tains a constant relation to S1. It is suggested that the PZ reflects the disparity in the duration of repolariza- tion of the ventricular myocardium and the specialized conducting system.

Effects of Conditioning on Plasma Catecholamine Levels During Exercise in Patients with Coronary Artery Disease

STEVEN WOLFSON*; ANTONIO E. ACOSTA; LESLIE I. ROSE; ALFRED F. PARISI; KARL ENGELMAN, San Antonio, Texas, and Philadelphia, Pennsylvania

_As an index of adrenergic activity during exercise (Ex) , arterial plasma catecholamine (Cat) levels were measured before and after a program of physical con- ditioning (Cond) . All 7 patients studied had a positive Ex test, and either angina or a remote myocardial in- farction. They were tested on a bicycle ergometer to angina or fatigue, and then trained on the bicycle for 10 to 18 weeks, 3 to 5 days/week. Cat levels were de- termined by a double-isotope derivative method. A Cond effect, with increased predicted max VOz (PMVO.,), was seen in 5. During Ex at 400 to 700 kpm/min, heart rate (HR) decreased from 147.3 + 6.5 to 126.7 2 6.4 P <O.OOl, whereas Cat decreased from 1.60 -C 0.27 to 0.73 2 0.07 CLg/liter, P <O.Ol. The 2 patients who did not undergo Cond did not man- ifest decreased HR, or increased PMV03, and Cat levels were slightly higher after training. At peak achieved work load, Cond patients had decreased HR and Cat after Cond; patients without Cond showed slight increases of each after training. These responses were significantly different, P <0.02. However, all pa-

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