William S. Stoney

Prophylaxis of atrial fibrillation with magnesium sulfate after coronary artery bypass grafting

Ninety-nine consecutive consenting patients were prospectively entered into a randomized, double-blind, placebo-controlled trial to determine the efficacy of postoperative magnesium therapy on the incidence of cardiac arrhythmias after elective coronary artery bypass grafting. No patient had documented or suspected arrhythmias preoperatively. Forty-nine patients received 178 mEq of magnesium given over the first 4 postoperative days, and 50 patients received only placebo. The clinical characteristics of both groups were similar. The preoperative mean serum magnesium concentration was similar in both study (1.90 mEq/L) and placebo (1.90 mEq/L) groups. The mean postoperative serum magnesium concentration in study patients was significantly elevated over postoperative days 1 through 4 when compared with preoperative levels (p less than 0.001). The postoperative mean serum magnesium concentration in control patients declined and remained significantly depressed through postoperative day 3 (p less than 0.001), but increased to preoperative levels by postoperative day 4. The mean serum magnesium concentration was significantly greater in the study patients as compared with the control patients over postoperative days 1 through 4 (p less than 0.001). Although there was no significant difference between groups with respect to episodes of ventricular arrhythmias, there was a significant decrease in the number of episodes of atrial fibrillation in the group receiving magnesium therapy (p less than 0.02). There were no recognized adverse effects of magnesium therapy. Prophylactic magnesium administration seems to lessen the incidence and severity of atrial fibrillation after coronary artery bypass grafting.

The Incidence of Venous Thrombosis Following Long-Term Transvenous Pacing

Long-term cardiac pacing with permanent transvenous electrodes has achieved wide acceptance with only occasional reports of venous obstruction and edema. To determine the incidence of venous abnormalities associated with transvenous electrodes, 34 venograms were obtained in 32 patients paced 18 months or longer. Eleven venograms demonstrated severe obstruction with collateral circulation communicating with the opposite cervical and innominate venous channels; 7 of these showed total occlusion. Seven venograms revealed no obstruction. The remaining 16 venograms showed venous stenosis without collaterals. It is concluded that venous abnormalities associated with permanent transvenous pacing occur commonly but are not usually associated with arm or facial edema.

A comparison of morphologic and angiographic findings in long-term internal mammary artery and saphenous vein bypass grafts☆

Internal mammary artery grafts are currently considered the conduits of choice for myocardial revascularization. Comparisons of long-term morphologic changes in internal mammary artery grafts and saphenous vein grafts and correlation with premortem angiography have not been reported. Eighteen internal mammary artery and 15 saphenous vein grafts that had been in place for 12 to 118 months (mean 56) in 18 patients were removed either surgically or at necropsy and examined histologically. Premortem angiograms were performed within 1 month of histologic study in 15 of these patients. Fibrointimal proliferation was more frequent in internal mammary artery than in saphenous vein grafts 8 [( 44%] of 18 versus 4 [27%] of 15; p = NS). In contrast, atherosclerosis was common in saphenous vein grafts but was extremely rare in internal mammary artery grafts (10 of 15 versus 1 of 18; p = 0.01). A good correlation was noted between the degree of narrowing estimated by angiographic and histologic measurements in both internal mammary artery grafts (d = 0.90) and saphenous vein grafts (d = 0.71). Accelerated atherosclerosis did not occur in internal mammary artery grafts, but was common in saphenous vein grafts. Fibrointimal proliferation was commonly associated with graft narrowing in internal mammary artery grafts and may be an important factor in late graft closure. This study also confirms that internal mammary artery grafts have greater longevity compared with saphenous vein grafts.

Videothoracoscopy improved technique and expanded indications

Current videoendoscopic technology and percutaneous techniques of exposure and dissection have been successfully applied to abdominal surgery with favorable results. Application of this technology to our practice of thoracoscopy is the basis of this report. Videothoracoscopy has been performed in 39 patients for the following indications: chronic pleural effusion, interstitial lung disease, mediastinal lymphadenopathy in lung cancer, persistent air leak after decortication, mediastinal mass, recurrent spontaneous pneumothorax, hydropneumothorax with persistent air leak, and pleural-based mass. The technique we employ includes lateral decubitus positioning and double-lumen endotracheal intubation with ipsilateral lung collapse. The videoscope, retractors, and instruments are introduced through separate 10-mm incisions. Percutaneous manipulation of instruments and the videoscope is guided by images produced on television screens without dissection, and if resection is performed, the incision is enlarged to allow specimen retrieval. Procedures performed using this technique include pleural biopsy, partial pleurectomy, lysis of adhesions, lung biopsies, staging lymph node biopsy, lung nodule biopsy, pleural-based mass resection, and mediastinal mass biopsy and resection. This videoendoscopic technique greatly improves visualization of thoracic anatomy, facilitating thoracoscopy and enhancing exploration of the chest. It is preferred over conventional thoracoscopy and, in some patients, reduces the magnitude of operation by avoiding thoracotomy.

Internal Mammary Artery Grafts: Technical Factors Influencing Patency

Eight hundred fourteen patients with internal mammary artery (IMA) coronary artery bypass grafts have been restudied 961 times with coronary arteriography, primarily to evaluate the patency of the grafts in the setting of symptomatic coronary occlusive disease. Their records were reviewed to assess graft patency as related to the technical aspects of coronary artery bypass surgery. Patency was evaluated using life-table analysis of the data. The method of harvesting the IMA played no role in patency. The left anterior descending coronary artery was the recipient coronary artery with the highest patency rate. The left IMA had a significantly higher patency rate than the right IMA. As a group, the IMAs had a significantly higher patency rate than saphenous vein grafts. However, there was no difference between right IMA grafts and saphenous vein grafts. The mammary artery grafts that remained patent throughout the study had a significantly higher blood flow after bypass than did those that became occluded (43.0 +/- 0.9 versus 28.9 +/- 1.8 ml/min; p less than .001).

Balloon Catheter Occlusion of the Ascending Aorta

Dense calcification of the ascending aorta predisposes to aortic injury and distal embolization when the aorta is cross-clamped or partially clamped in the performance of cardiac operations. We occluded the ascending aorta with a Foley balloon catheter in 2 patients undergoing aortocoronary bypass grafting. The technique used is described in this report.

Cloth disruption in the Starr-Edwards composite mitral valve prosthesis.

Abstract Two cases of seat cloth wear in the Model 6310 composite cloth-covered Starr-Edwards mitral valve prosthesis are reported. In both patients a hemodynamically significant paravalvular leak was present directly opposite the area of cloth wear. It is postulated that the poppet is deflected so as to seat abnormally under these circumstances, striking the struts and cloth directly opposite the leak. An aggressive attitude toward replacement of the 6310 Starr-Edwards mitral prosthesis in the presence of a paravalvular leak is suggested.

Urgent operation for acquired ventricular septal defect.

Recent experience suggests that ventricular septal defect (VSD) secondary to myocardial infarction constitutes an indication for urgent operation. Acquired VSD at St. Thomas Hospital, Nashville, was reviewed to substantiate the obsolescence of protracted medical therapy designed to allow a late, technically less demanding, repair. Twenty-two acute VSDs (less than four weeks following onset of murmur) have been treated since 1970. Five patients died during medical therapy. Two patients survived for more than four weeks without operation. One never manifested significant cardiac decompensation. The other was operated on at 33 days, after progressive deterioration. No technical advantage from the delay was apparent, although survival was achieved. Ten of IS patients (67%) operated on during the first four weeks survived. Fourteen had reached a level of marked instability prior to operation. Of the five deaths, four were technical and were the product of an initial lack of recognition of the necessity for patch replacement of the interventricular septum. The prosthetic patch is now considered essential to minimize suture-line stress in necrotic muscle. Potentially, only one of 15 patients operated on early using current methods would have expired. This experience supports an aggressive surgical approach to any unstable patient with postinfarction VSD. Early repair requires specific techniques. Results of early operation using these techniques are dramatically superior to past efforts designed to delay definitive repair.

Further evaluation of the surgical treatment of obstructive disease of the left main coronary artery.

A protocol for the operative management of two patient groups with left main coronary artery disease has been evaluated. The period prior to and during induction of anesthesia is managed without using aortic balloon counterpulsation. Of the 86 patients undergoing coronary artery bypass for left main coronary artery disease from 1970 to 1973, there was a surgical mortality of 8.1%. Follow-up of the survivors from 48 to 87 months revealed three coronary and five non-coronary related deaths with survival to seven years of 75.6 ± 5%. If the operative mortality is excluded, there is an observed survival to seven years of 82.4 ± 4.8%, almost the same as a “normal” population of similar age and sex. Utilizing the same protocol, 90 similar patients undergoing coronary artery bypass in 1976 had an operative mortality of 4.4%. The deaths were not related to induction of anesthesia. The perioperative infarction rate (2%) and postoperative cardiac enzyme determinations were no greater in a random group having the same operation for less severe forms of coronary artery disease during the same time period. This method of management for patients with significant left main coronary artery disease is judged superior to other more complex techniques.