Michael S. Feldman

Nitroglycerin to Unmask Reversible Asynergy Correlation with Post Coronary Bypass Ventriculography

The value of nitroglycerin in determining the potential reversibility of asynergy was examined in 35 patients with coronary heart disease. Ventriculograms performed at rest and after sublingual nitroglycerin were analyzed for (1) location of asynergy relative to distribution of the 3 major coronary arteries and (2) severity of asynergy. Of the 41 hypokinetic zones, 30(73%) improved following nitroglycerin. Of 28 akinetic zones, 16 (57%) improved (7 of the 16 segments becoming normal) following nitroglycerin. None of 7 dyskinetic zones showed change following nitroglycerin. Twelve patients were restudied following coronary bypass surgery. There was an excellent over-all correlation between the segments that responded to nitroglycerin and bypass surgery in those segments with open grafts. Eighteen segments which improved following nitroglycerin had patent postoperative grafts, and in 15 segments there was a corresponding improvement following bypass surgery. Two segments which were unresponsive to nitroglycerin preoperatively had patent postoperative bypass grafts. Neither segment improved despite graft patency. In summary, sublingual nitroglycerin is useful in unmasking residual contractile ability in asynergic zones. A positive response to nitroglycerin appears to be predictive of corresponding beneficial effect from a coronary bypass graft. The data strongly suggest that the use of nitroglycerin to determine residual contractile ability may be of considerable value in better defining the potential risks and benefits of coronary bypass surgery.

Magnetic resonance imaging to evaluate patency of aortocoronary bypass grafts.

To assess the efficacy of magnetic resonance (MR) imaging in evaluating graft patency after coronary bypass surgery, 20 patients who had prior surgery (average 5.5 years, range 1.5 to 14) and recent cardiac catheterization because of chest pain were studied. No patient had surgical intervention or change in symptoms in the time interval between catheterization and MR imaging. These 20 patients had a total of 47 grafts, defined as proximal anastomoses: 20 to the left anterior descending or diagonal artery (LAD), 13 to the left circumflex artery marginal branches (LCX), and 14 to the right coronary artery or posterior descending artery (RCA). The patients underwent cardiac and respiratory gated MR scans in a 0.5 tesla magnet with an echo time of 22 msec and two repetitions in a 128 X 256 matrix. In-plane resolution was 2.7 mm. Every patient had a scan in the transaxial plane and some underwent scanning in the sagittal and coronal planes as well. A graft was considered patent by MR when a signal-free lumen was visualized in an anatomic position consistent with that of a bypass graft, had a lumen larger than the native vessels, was seen on more than one slice, and was seen at a level higher than that of the native vessels. If a known graft was not seen it was considered occluded. The scans were interpreted by consensus of two physicians aware of the operative but not the cardiac catheterization data.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of Nifedipine in Rest Angina Refractory to Propranolol and Nitrates in Patients with Obstructive Coronary Artery Disease

Nineteen patients with recurrent rest angina were given oral nifedipine. All patients had chest discomfort refractory to propranolol and oral or topical nitrates given to tolerance. The addition of nifedipine, 30 to 120 mg daily, abolished rest angina in 14 patients, decreased its frequency in two, and had no effect in three patients. Five of seven patients on long-term nifedipine (mean, 6.2 +/- 3.4 months) remained free of rest pain. Of seven patients who had their nifedipine dose decreased or discontinued, five had recurrent rest angina. Of the 19 patients, 16 had coronary angiography. Five had three- vessel obstructive disease (greater than 75% lesion), six had two-vessel obstructive disease, and five had one-vessel obstructive disease. The remaining three unstudied patients had pathologic Q waves in the ECG. Thus nifedipine appears to be an efficacious agent in the treatment of refractory rest angina in patients with obstructive coronary artery disease.

Transtelephonic monitoring of 25,919 implanted pacemakers.

In order to evaluate the behavior of lithium‐powered cardiac pacemakers, a database 25,919 lithium‐powered pacing systems including 23,517 single and 2,402 dual chambered pacemaker generators were followed in 21,750 patients. Of this group, 11,319 were currently active in addition to 7,560 who died, as well as 2,871 patients who terminated their follow‐up service prior to the end‐of‐life of the pacemaker system. A total of 23,517 single chambered pacemakers were followed for 719,173 months of pacing. The mean time to explant for generator malfunctions was 42 months and for all pacing system malfunctions it was 38 months compared to 31.9 months and 28.6 months, respectively, for the 2,402 dual chambered units that were observed for 38,718 months. In the single chambered units, the most frequent reason for explant was battery exhaustion (37% of explants) followed by lead problems (26%) compared to 49% and 12%, respectively, for the dual chambered units. The incidence rates, defined as a transtelephonic test result, required physician decision for action or clarification of the pacing mode or program parameters and showed a high incidence rate immediately post‐implant; thereafter, there was a relatively trauble‐free period until the 36th month when capture, sensing, and battery problems began to occur at a steady rate reaching 4% at the end of 48 months. Similarly, for dual chambered units, an 8% incidence rate was seen within the first 3 months, followed by a quiescent period until the 28th month when the incidence rate jumped to 16%. An analysis of 28 series of pacemakers, manufactured by 10 different pacemaker companies in which projected longevity data was available, indicated that an average of only 63% of the projected longevity of the units was realized for single chambered pacemakers. It is concluded that the actual longevity of single chambered units is less than the projected one originally stated and the present data derived from cumulative survival of dual chambered pacemakers does not suggest a brighter outlook, but rather portends an even higher frequency of pacemaker incidence and failure rate.

The use of echocardiography in determination of reversible posterior wall asynergy

Recent studies have indicated that nitroglycerin can be delineate potentially reversible asynergic zones depicted ventriculographically. To assess the ability of the echocardiogram to detect reversible asynergy, posterior wall motion was assessed in 19 patients both echocardiographically and ventriculographically before and after nitroglycerin. Thirteen of the 19 patients demonstrated abnormal posterior wall motion both by echocardiography and ventriculography while six were normal by both techniques. In 4 of the 13 asynergic areas, posterior wall excursion improved following nitroglycerin (from 0.99 +/- .07 to 1.30 +/- .07 cm. by echocarciography (p less than .025) with a corresponding improvement in hemiaxis shortening from 12.0 +/- 6.1 per cent to 29.0 +/- 6.7 per cent (p less than .02). In contrast, in nine patients in whom inferior segment hemiaxis shortening was unchanged following nitroglycerin, posterior wall excursion by echocardiography was similarly not improved (1.01 +/- .03 cm. before and 1.02 +/- .03 cm. after nitroglycerin). The effect of nitroglycerin on posterior wall velocity paralleled changes in posterior excursion. The six patients with initially normal posterior excursion showed no significant change by either echocardiography or ventriculography following nitroglycerin. Thus, the echocardiogram is of considerable value in detecting both the presence and potential for improvement of asynergic posterior wall segments.