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Biomedical subjects

D H Tyras

Publications and source records attributed to D H Tyras.

At least 37 records · Page 2Linked to original sources
PubMed1981

Effect of coronary bypass surgery on survival patterns in subsets of patients with left main coronary artery disease. Report of the Collaborative Study in Coronary Artery Surgery (CASS).

The 3 year cumulative survival rate of 1,492 patients with left main coronary artery disease (50 percent or greater stenosis of luminal diameter) enrolled in the Collaborative Study in Coronary Artery Surgery (CASS) was 91 percent for the surgical group and 69 percent for patients treated medically (p less than 0.0001). Mortality was significantly greater in patients with impaired left ventricular function. The difference between medical and surgical therapy was significant for patients who had normal, moderately abnormal and severely impaired left ventricular function and for patients with stenosis of the left main coronary artery of 50 to 59, 60 to 69, 70 to 79 and 80 percent or greater. Aortocoronary bypass surgery did not significantly improve survival in patient subgroups who had (1) a nonstenotic dominant right or balanced coronary circulation, (2) a stenotic dominant right coronary artery and normal left ventricular function, and (3) left main coronary stenosis of 50 to 59 percent and normal or mildly abnormal left ventricular function. The Cox proportional hazards model was used to select baseline variables that were independent predictors of long-time mortality. The model selected left ventricular score, age, congestive heart failure score, hypertension, percent left main coronary arterial stenosis and coronary arterial dominance as the baseline variables most predictive of long-term survival. A clinical and angiographic prognostic risk index developed from these six baseline variables showed significantly improved survival for the surgical cohort in each of four risk categories. In the best and worst risk category, the 3 year survival rate was 97 and 82 percent, respectively, for the surgical group and 85 and 34 percent, respectively, for the medical group (p less than or equal to 0.0002). The data from this observational study show that coronary bypass surgery prolongs life in most patients with left main coronary artery disease, particularly those who have severe narrowing of the left main coronary artery or impaired left ventricular function. The results permit a better understanding of the natural history of left main coronary artery disease and permit a more accurate estimate of long-term survival for individual patients through the use of a clinical-angiographic risk index.

Cardiac Catheterization↗
PubMed1981

Continuous hydralazine infusion for afterload reduction.

Impedance reduction with a continuous infusion of hydralazine was evaluated in 20 patients following cardiopulmonary bypass. Patients were selected for therapy when the cardiac index (CI) was less than 2.2 L/m2/min, when the systemic vascular resistance index (SVRI) was greater than 2,500 dyne sec cm-5, or when both conditions were present. No other vasoactive or cardiotonic drugs were used intraoperatively or postoperatively. Responses were measured at 15, 30, 60, 120, 180, and 240 minutes and compared with control measurements. Significant responses appeared by 15 minutes in the mean arterial pressure, CI, and SVRI, which were maximal by 2 hours. At 4 hours, the SVRI was 1,520 +/- 276 dyne sec cm-5 (control, 3,235 +/- 222) and pulmonary vascular resistance index, 365 +/- 102 dyne sec cm-5 (control, 592 +/- 71). The CI was 3.20 +/- 0.29 L/m2/min (control, 1.96 +/- 0.16) and mean arterial pressure, 75 +/- 2.3 mm Hg (control, 92 +/- 2.4). Left atrial, pulmonary artery diastolic, and right atrial pressures increased from control but not significantly: 11.4 +/- 0.8 to 13.3 +/- 1.2 mm Hg, 13.6 +/- 1.6 to 17.2 +/- 1.5 mm Hg, and 6 +/- 1.6 to 9.4 +/- 1.7 mm Hg, respectively. In 16 patients, hydralazine was continued for 24 hours and in 11, the transition to oral therapy was made. Hydralazine by infusion effectively reduces after load, avoids the fluctuations of bolus therapy, and allows the transition to oral therapy if needed.

Blood Pressure↗
PubMed1981

Angiographic prevalence of high-risk coronary artery disease in patient subsets (CASS).

The prevalence of coronary artery stenoses greater than or equal to 70% or left main stenosis greater than or equal to 50% was evaluated in 20,391 patients who underwent angiography in the Coronary Artery Surgery Study from 1975-1979. After the patients with unstable angina or myocardial infarction were excluded, the disease prevalence in the 8157 patients with definite angina, probable angina, and nonspecific chest pain was 93%, 66% and 14% in men and 72%, 36% and 6% in women (p less than 0.001). The age and sex of the patients and character of chest pain were important determinants of disease prevalence and severity. Left main or three-vessel coronary disease occurred in more than 50% of middle-aged men and older women with definite angina and in more than 50% of men who had probable angina and were older than 60 years of age. In contrast, left main coronary disease occurred in less than 2% of 1282 men and less than 1% of 1397 women with nonspecific chest pain regardless of age. In this latter patient subset, less than 5% of men and less than 1% of women in each decade under 60 years had left main or three-vessel coronary artery disease. Thus, high-risk coronary disease is common in middle-aged patients with definite angina and older patients with probable angina, but is rare in patients with nonspecific chest pain. Indications and guidelines for diagnostic noninvasive tests and coronary angiography could be based on these results.

Adult↗
PubMed1981

Left main equivalent: results of medical and surgical therapy.

Stenosis of at least 50% of both the left anterior descending and circumflex coronary arteries proximal to their major branches has sometimes been called left main equivalent (LME) disease. During a 4-year interval, 189 LME patients were identified as surgical candidates by angiographic criteria. Coronary artery bypass grafting (CABG) was performed in 119 patients; 70 patients were managed nonoperatively. Treatment assignment was nonrandom. During the same interval, 203 patients with significant left main coronary artery (LMCA) stenosis and 742 patients with three-vessel disease without LMCA or LME stenosis underwent CABG. Follow-up is 99.2% complete at an average of 48 months (range 24--73 months). Operative mortality was significantly higher among LMCA patients (4.0%) than among LME surgical patients (0.8%) (p less than 0.05). Cumulative 5-year survival was better among LME surgical patients (98.2 +/- 1.3%) than among LME medical patients (75.9 +/- 5.7%) (p less than 0.0001) or LMCA surgical patients (92.8 +/- 2.1%) (p less than 0.03). All operative patient groups had a significantly lower incidence of myocardial infarction (10.3--13.4%) than the LME medical patients (25.7%) (p less than 0.05). Relief of angina was also significantly better in the operative groups (61--67.6%) than in LME medical patients (36%) (p less than 0.005). Major differences exist between LME and LMCA patients; LME is more properly considered a variant of multivessel coronary artery disease. Results of medical and surgical therapy suggest that patients with LME disease should be strongly considered for early operative therapy.

Aged↗
PubMed1980

Operative risk factors in patients with left main coronary-artery disease.

To identify the factors associated with operative mortality, we evaluated clinical, angiographic, and surgical variables in 1172 patients with left main coronary-artery stenoses of at least 50 per cent, who underwent coronary-bypass procedures in the Collaborative Study in Coronary Artery Surgery (CASS). The operative mortality was 4.2 per cent overall and was less than 3 per cent in seven of the 15 participating hospitals. Historical variables associated with an increase in operative mortality were age, female sex, and duration and severity of angina. Other variables associated most closely with poor survival were urgency of operation, left coronary-artery dominance, severity of left main coronary-artery stenosis, and impairment of left ventricular contraction. The results of this multicenter study show that aortocoronary bypass surgery in patients with left main coronary-artery disease can be performed with a low mortality and that patients at high risk can often be identified before surgery.

Age Factors↗
PubMed1980

Clinical experience with cold blood as the vehicle for hypothermic potassium cardioplegia.

Intermittent cold ischemic arrest was compared with hypothermic potassium cardioplegia using cold blood as the vehicle in two consecutive series of patients having isolated coronary bypass grafting. Between January 1, 1977, and June 30, 1977, 196 patients were operated on using cold ischemic arrest. The incidence of perioperative infarction was 14.3%, and mean total myocardial ischemia time was 42 +/- 1.2 minutes. From July 1, 1977, to June 30, 1978, there were 428 operations done using cold blood with potassium. The incidence of perioperative infarction was 5.6% (p less than 0.005), and the mean total myocardial ischemic time was 80 +/- 2.1 minutes. In the five years prior to this study, the incidence of perioperative infarction was constant at 13% while operative mortality was declining from 5 to 1% and the need for postoperative myocardial support was declining also. Use of cold blood potassium cardioplegia compared with cold ischemic arrest for myocardial protection during coronary artery operations has significantly reduced the incidence of perioperative infarction while doubling cross-clamp time.

Aspartate Aminotransferases↗
PubMed1980

The effect of coronary artery bypass on longevity. A surgeon's viewpoint.

Enthusiasm for new therapeutic modalities frequently results in a ground swell of overuse, which recedes to leave a trough of negativism before a definitive level is established. In the case of CABG, the ground swell has become a 10-year flood tide, without an ebb, although ripples have marred the surface. It is generally agreed that suitable control populations are needed to determine the role of a therapy and that the best controls would arise from randomized prospective trials. At present, the best randomized trial is the VA study which has shown that operation does not enhance longevity for single vessel disease, but clearly does for left main coronary disease. In those individuals with two- and three-vessel disease, the VA study has not shown that surgical therapy is better than medical treatment. However, three other studies containing patients selected by the VA criteria indicate that operation provides significantly greater longevity for patients in these two categories. Acceptance of this position requires acknowlegement of the validity of the VA study and the comparison of extramural concurrent surgical series.

Coronary Artery Bypass↗
PubMed1980

The rationale for operative therapy of symptomatic single-vessel coronary artery disease.

During an 8 year interval, 184 patients with symptomatic single-vessel disease underwent coronary artery bypass grafting (CABG). There were no operative deaths and only one late cardiac death (5 year cumulative survival 97.9%). At 48 months mean follow-up, 91% are angina free or improved. The low incidence of perioperative and late myocardial infarction (MI) and the preservation of ventricular function seen on follow-up catheterization suggest that coronary bypass operations yield significant benefits in severely symptomatic patients with single-vessel disease. Evidence is presented which supports the idea that single-vessel coronary artery disease may be a unique manifestation of coronary atherosclerosis and not one stage in a continuum.

Angiocardiography↗
PubMed1980

Bypass grafts to the left anterior descending coronary artery: saphenous vein versus internal mammary artery.

During the interval 1972 to 1977, of 1,522 patients undergoing isolated coronary artery bypass grafting (CABG), 1,459 received grafts to the left anterior descending coronary artery (LAD). Internal mammary artery (IMA) was used in 765 patients and reversed saphenous vein graft (SVG) in 694 patients. Choice of bypass graft was nonrandom. Clinical follow-up is available in 98% of patients. Angiography has been obtained in 69% of eligible patients at 1 month, 65% at 1 year, 62% at 3 years, and 63% at 5 years. There was no difference in operative mortality rates (IMA 1.4%, SVG 1.9%) or 5 year actuarial survival rates (IMA 87.6%, SVG 88.7%). Graft flows were consistently higher at operation with the SVG, but patency rates at each interval were significantly higher with the IMA. Perioperative and late myocardial infarction occurred significantly less often in IMA patients. Superiority in IMA graft patency became apparent after an initial "learning curve" of 2 years of experience. Maintenance and/or restoration of normal left ventricular function was more common in IMA patients operated upon after the initial 2 year experience. IMA grafts are recommended for LAD bypass when the LAD is 2.0 mm in diameter or less. Early results with sequential SVG to the LAD suggest that this may be a realistic alternative to the IMA and may approach the 1 year IMA graft patency rate of 92.6%.

Angina Pectoris↗
PubMed1979

Long-term results of myocardial revascularization.

During 1970 to 1977, among 1,733 patients who underwent isolated coronary bypass grafting, the operative mortality was 2.5 percent. Actuarial 5 year survival is 88.1 percent. At an average follow-up of 46 months (range 13 to 108), 90 percent of patients remain angina-free or with symptomatic improvement. The 5 year survival rate of patients with single vessel coronary artery disease is 97.9 percent. In patients with multivessel disease, operative survival appears to be favorably influenced by the presence of normal preoperative ventricular function. Late survival is significantly better in patients with multivessel disease with normal preoperative ventricular function or with complete revascularization. Risk of perioperative myocardial infarction has been appreciably reduced by the introduction of cold potassium chloride cardioplegia. Late myocardial infarction has occurred at an average annual risk of 1.46 percent. These data show that long-term survival and a small incidence of late myocardial infarction after myocardial revascularization are more likely in patients who undergo complete revascularization before significant left ventricular myocardial damage has occurred.

Adult↗
PubMed1979

Cold blood as the vehicle for potassium cardioplegia.

Cold blood with potassium, 34 mEq/L, was compared with cold blood and with a cardioplegic solution. Three groups of 6 dogs had 2 hours of aortic cross-clamp while on total bypass at 28 degrees C with the left ventricle vented. An initial 5-minute coronary perfusion was followed by 2 minutes of perfusion every 15 minutes for the cardioplegic solution (8 degrees C) and every 30 minutes for 3 minutes with cold blood or cold blood with potassium (8 degrees C). Hearts receiving cold blood or cold blood with potassium had topical cardiac hypothermia with crushed ice. Peak systolic pressure, rate of rise of left ventricular pressure, maximum velocity of the contractile element, pressure volume curves, coronary flow, coronary flow distribution, and myocardial uptake of oxygen, lactate, and pyruvate were measured prior to ischemia and 30 minutes after restoration of coronary flow. Myocardial creatine phosphate (CP), adenosine triphosphate (ATP), and adenosine diphosphate (ADP) were determined at the end of ischemia and after recovery. Changes in coronary flow, coronary flow distribution, and myocardial uptake of oxygen and pyruvate were not significant. Peak systolic pressure and lactate uptake declined significantly for hearts perfused with cold blood but not those with cold blood with potassium. ATP and ADP were lowest in hearts perfused with cardioplegic solution, and CP and ATP did not return to control in any group. Heart water increased with the use of cold blood and cardioplegic solution. Myocardial protection with cold blood with potassium and topical hypothermia has some advantages over cold blood and cardioplegic solution.

Adenosine Diphosphate↗
PubMed1979

Ventricular function and the native coronary circulation five years after myocardial revascularization.

Of 531 patients who underwent coronary artery bypass grafting during 1970 to 1973, 181 were restudied by ventriculography and by graft and coronary angiography at least 5 years following operation. Five patterns of postoperative ventricular function were identified: improved ventricular function resulting in normal left ventricular (LV) function; normal ventricular function that was unchanged; abnormal ventricular function that improved but did not reach normal; abnormal ventricular function that remained unchanged; and deterioration of LV function. Patients who regained (40) and those who retained normal ventricular function (49) comprise 49% of the series and patients with deterioration of ventricular function, only 20%. Graft patency and angina relief were significantly better in those with normal LV function than in those with LV deterioration. Progression of disease in grafted coronary arteries was similar in all groups, but was significantly higher in ungrafted coronary arteries (61.3%) in the patients showing deterioration than in either the improved patients or those with an unchanged normal LV (33.3% each) (p less than 0.05). The high incidence of progression of disease in ungrafted coronary arteries in the group with deterioration suggests that low graft patency and deterioration of ventricular function in this group might both be related to intrinsic acceleration of coronary atherosclerosis unrelated to operative intervention.

Angina Pectoris↗
PubMed1979

Supraventricular tachyarrhythmias after myocardial revascularization: a randomized trial of prophylactic digitalization.

The success of prophylactic digitalization in reducing the incidence of supraventricular tachyarrhythmias (SVT) was studied in 140 randomly grouped, consecutive patients undergoing myocardial revascularization operations. The test group received either 1 or 1.5 mg. of digoxin the day before operation and were maintained postoperatively on 0.25 mg. of digoxin daily. There was a significant increase (p less than 0.05) in the incidence of SVT in the treated patients (17 of 61 or 27.8 percent) vs. the untreated patients (nine of 79 or 11.4 percent). There was no significant difference in SVT with the two digitalization dosage levels (31.6 percent with 1 mg. vs. 21.7 percent with 1.5 mg.). Prophylactic digitalization demonstrates no benefit in the prevention of SVT following myocardial revascularization and may, in fact, predispose the patient to these arrhythmias.

Coronary Artery Bypass↗
PubMed1978

Paraplegia following intraaortic balloon assistance.

In a patient receiving intraaortic balloon counterpulsation following myocardial revascularization, paraplegia developed two days post-operatively. Postmortem examination demonstrated a dissecting hematoma of the thoracic aorta and spinal cord infarction. The neurological deficit is thought to be due to embarrassment of spinal cord blood supply, and mechanisms of injury are discussed.

Acute Kidney Injury↗
PubMed1978

Myocardial revascularization in women.

During the period January, 1970, through June, 1977, 1,541 patients underwent coronary artery bypass grafting; 241 of them were women (15.6%). Operative mortality rates for the entire study were 2.4% in men and 3.7% in women, but they showed a marked decline in women during 1975 to mid-1977, with only 2 deaths in 140 patients (1.4%). Women comprised a larger percentage of patients (16.7%) in these later years. Women were slightly older, received fewer grafts, had better preservation of ventricular function on preoperative studies, and had more severe anginal symptoms than men. Patency rates were significantly lower in women at 1 month, 1 year, and 3 years. Five-year survival was not significantly different between women (88.3%) and men (93.5%). Many of these findings may be explained on the basis of women having smaller coronary arteries than men. These favorable results differ from earlier reports of higher mortality rates in women and indicate that myocardial revascularization should not be withheld from female patients.

Age Factors↗
PubMed1978

Late sequelae of perioperative myocardial infarction.

The late suquelae of myocardial injury occurring at the time of direct myocardial revascularization are unknown. Fifty of 500 consecutive patients undergoing aortocoronary bypass grafting developed both electrocardiographic and enzymatic evidence of myocardial injury. They were matched with 50 patients of similar age, sex, history of previous infarction, severity of angina, degree of coronary arteriosclerosis, and level of ventricular function as determined by preoperative angiographic studies. The conduct of the operation was identical in each group except for prolongation of total cross-clamp time in those patients with myocardial injury. The total number of vessels grafted, the conduit used, and the operative mean graft flow were similar. Results of treadmill stress testing at 24 to 36 months were not significantly different between groups. Angina status, long-term survival, graft patency, and ventricular function were not adversely affected by intraoperative myocardial injury. However, postoperative ventricular function and stress test performance were related to graft patency.

Adult↗
PubMed1978

Myocardial revascularization: a rebuttal of the cooperative study.

From January 1972 through December 1974, at Saint Louis University Medical Center (SLU), 345 patients similar to those of the VA Cooperative Coronary Artery Study received CABG. Operative mortality was SLU 2.3%, VA 5.6% (p < 0.05). Perioperative myocardial infarction rate was SLU 8.4%, VA 18% (p < 0.005). One year graft patency was SLU 87%, VA 71%; all grafts patent SLU 76%, VA 54%; at least one graft patent SLU 96%, VA 89%. SLU angina pectoris relief at five years was 90%. SLU patients free of myocardial infarction five years postoperatively was 83%. Comparative cumulative four year survivals were: [Table: see text] Cumulative four-year survival in 272 SLU patients (79%) completely revascularized was 94%, compared to SLU entire group of 95%, VA medical 86% (p < 0.002) and VA surgical 85% (p < 0.002). Comparing 1972-74 SLU results to VA medical and surgical groups, CABG prolonged life in patients with double and triple vessel disease and in those completely revascularized.

Adult↗