Biomedical subjects
Publications and source records attributed to B C Morton.
Combined forms of left ventricular outflow obstruction are being recognized with increasing frequency. A patient who had coarctation of the aorta, valvular aortic stenosis, and fixed and dynamic subvalvular obstruction is described. The importance of recognizing multiple levels of obstruction in such patients is emphasized.
Hemodynamic monitoring in the critically ill patient requires the use of sophisticated electronic devices. To use this equipment one should have a general understanding of the principles involved and the requirements of a reliable system. This communication serves to explain the requirements of the various components of a hemodynamic monitoring system and to demonstrate how they interact to produce accurate and safe electronic signals from mechanical wave forms obtained from the patient.
In 16 patients who underwent endarterectomy of the left anterior descending (LAD) coronary artery combined with saphenous vein bypass grafting between Aug. 1, 1976 and July 31, 1978, the results of preoperative and postoperative angiography were comparable. Most patients had obstruction or severe stenosis of the proximal LAD coronary artery together with a poor runoff as demonstrated angiographically. Eighteen vein grafts were placed in the LAD artery and 15 (83%) were satisfactorily patent. Six of 18 grafted arterial segments became occluded distal to the site of graft insertion, but in most cases there was sufficient proximal runoff to maintain graft patency. In this study intraoperative measurements of graft flow were predictive of graft or distal vessel patency, or both. Careful postoperative assessment of the results of this technique seems warranted.
The influence of smoking, hyperlipidemia, and glucose intolerance on graft patency and rate of progression of obstructive disease in the native circulation was assessed in 99 patients 1 1/2 years after aortocoronary bypass grafting. There were 24 patients in whom none of these risk factors was identified. There were 42 patients with one, 29 with two, and four with three risk factors. Overall graft patency rate was 74%. Graft patency was not significantly influenced by any of these factors either singly or in combination. Progression of obstructive disease in both proximal and distal segments of grafted vessels and in nongrafted vessels was not significantly increased by the presence of one, two, or three risk factors. Over all, there was progression in 56% of segments proximal to grafts, in 8% distal to grafts, and in 14% of nongrafted vessels. Longer term studies will be required to establish any adverse influence of these risk factors on saphenous vein bypass grafts and native circulation.
During a 5-year period (Apr. 14, 1970 to Apr. 14, 1975) 930 patients underwent aortocoronary bypass grafting; the procedure was done as an emergency in 141. Of the entire group 3.3% died at operation, 1.6% died in hospital and 5.8% died later; of the patients undergoing emergency grafting 12.1% died at operation and 5.7% died later. From a detailed analysis of the first 600 patients it was found that both operative and late mortality were clearly related to two factors: severe left ventricular dysfunction at the time of operation and inadequate surgical treatment because of insertion of insufficient numbers of grafts or because of poor blood flow through the grafts.
Myocardial infarction has been noted as a frequent complication of coronary artery surgery in many review series, although its causes are uncertain. Follow-up of 100 patients at 19.7 months (mean) after coronary bypass surgery identified 15 patients with perioperative myocardial infarction as judged by new, significant Q waves after surgery. There were no significnat differences in age, preoperative anginal class, previous infarction, presence of hypertension, hyperlipidemia, or frank glucose intolerance compared with the 85 patients without infarction. Nor was there a significnat difference in coronary artery score, left ventricular end-diastolic pressure, cardiac index, or presence of collaterals. Cardiopulmonary bypass time, duration of anoxic arrest, and number of vessels grafted did not differ. Perioperative infarction always occurred in the territory of a grafted vessel and not in comparably compromised, nongrafted areas. In 13 cases new Q waves appeared in the first 24 hours, and myocardial infarction was not clinically suspected. Eight of the 15 grafts at risk were patent at late follow-up. Mean ejection fraction was not significantly changed postoperatively, but affected segmental wall motion declined in most cases. Five patients with perioperative infarction but no patent grafts improved by only 1 NYHA class (mean), but ten patients with infarction and one or more grafts patent improved by 2.9 NYHA classes (mean). Perioperative infarction could not be correlated with currently recognized patient and operative risk factors. The consistent anatomical relationship suggested that the grafting procedure itself was critical to the occurrence of distal segmental infarction.
One hundred patients were evaluated 12 to 43 months after saphenous vein bypass surgery. The rate of progression of obstructive disease in the native vessels and changes in collateral circulation were analyzed in detail. Fifty-five per cent of preoperatively patent vessels showed progression proximal to the site of graft insertion, 40% proximal to patent grafts; there was distal progression in only 7% of grafted vessels. The progression rate for nongrafted vessels was 14%. Patent grafts were associated with a high rate of disappearance of collaterals to the grafted vessels, while occluded grafts were associated with preservation of collaterals or appearance of new collaterals. Progression of obstructive disease in the native circulation and changes in collaterals did not prevent symptomatic improvement (93% of patients were symptomatically improved).
The availability of newer and more expensive low osmolar contrast agents for cardiac angiography has forced a comparison with the standard ionic contrast agents. The milder hemodynamic effects of low osmolar agents make them the contrast of choice for the sickest patients; however, the existence of a reduction in the rate of anaphylactoid reactions or death during catheterization seems more doubtful. Guidelines for the selective use of the agents in the cardiac catheterization laboratory are offered, based on one hospital's experience of more than 20,000 procedures.
The morphologic effects of percutaneous transluminal coronary artery balloon angioplasty (PTCA) on atherosclerotic vessels is described in six patients who died at varying intervals after the procedure (four early and two late). In the early group (less than one week post PTCA) one patient died because of electromechanical dissociation during emergency PTCA for evolving infarct; in the three other patients PTCA was performed for left main occlusion and cardiogenic shock with deaths 3, 24 and 25 h after PTCA. The two late deaths were patients who died one and nine months after PTCA from unrelated causes. There were 12 sites of balloon inflation in the six patients, all in left main, isolated marginal or left anterior descending arteries. Post mortem examinations, with in toto serial sectioning of the ballooned coronary arteries, revealed a number of local morphologic changes. Plaque fractures and disruptions of the arterial wall to variable depths were observed. At four sites these fractures were through media, and at one site was associated with a large dissection. These cases had only small epicardial hemorrhages or reactive adventitial changes associated with these deep fractures. Four of the six patients had intramural arterial emboli (athero/thrombo/calcium/foreign body). These findings confirm that a large part of the effect of PTCA is due to physical disruption of plaque and underlying native vessel.