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Biomedical subjects

C L McIntosh

Publications and source records attributed to C L McIntosh.

At least 37 records · Page 2Linked to original sources
PubMed1990

Comparative assessment of chordal preservation versus chordal resection during mitral valve replacement.

Left ventricular function often deteriorates after mitral valve replacement for mitral regurgitation. It has been postulated that disruption of the mitral valve apparatus at operation is a major mechanism of postoperative dysfunction. The hypothesis tested in this investigation was that chordal preservation results in more favorable left ventricular function. Sixty-nine patients with isolated mitral regurgitation who underwent mitral valve replacement were studied before and 6 months after operation by treadmill exercise testing, catheterization, echocardiography, and radionuclide angiography. Nine patients underwent mitral valve replacement with preservation of the entire mitral apparatus and five with preservation of the posterior leaflet and attached chordae. The remaining 55 had mitral valve replacement with complete excision of the native valve. Preoperatively, there were no differences among groups in age, gender, exercise capacity, cardiac index, rest or exercise ejection fraction, fractional shortening, or pulmonary artery pressures. There were four perioperative deaths (7%) and eight late deaths among the 55 patients with chordal resection but no early or late deaths of patients whose chordae were preserved (p = 0.05). In patients in whom the chordae were excised, exercise capacity, left ventricular systolic dimensions, and cardiac index did not improve after mitral valve replacement, and left ventricular function deteriorated, as evidenced by a reduction of both the resting and exercise ejection fractions (from 46% +/- 13% to 31% +/- 13%, p = 0.0001, and from 49% +/- 12% to 37% +/- 14%, p = 0.0007, respectively) and fractional shortening (from 34% +/- 10% to 26% +/- 14%, p = 0.0001). In contrast, exercise capacity improved after mitral valve replacement in patients in whom the entire apparatus was spared (by 4 +/- 3 minutes, p = 0.05), left ventricular systolic dimensions decreased (from 44 +/- 8 to 36 +/- 9 mm, p = 0.03), and left ventricular function was maintained or improved, as evidenced by preservation of the resting ejection fraction (preoperative, 50% +/- 14%; postoperative, 54% +/- 11%; p = no significant difference), exercise ejection fraction (46% +/- 16% versus 52% +/- 9%, p = no significant difference), fractional shortening (from 31% +/- 9% to 28% +/- 9%, p = no significant difference), and an increase in the cardiac index (from 2.0 +/- 0.3 to 2.7 +/- 0.5 L/min/m2, p = 0.05). No statistically significant differences between posterior chordal resection only and preservation of the entire apparatus were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

The results of operation in patients with hypertrophic cardiomyopathy and pulmonary hypertension.

The clinical course and hemodynamic results in patients undergoing operation for obstructive hypertrophic cardiomyopathy with preoperative pulmonary arterial hypertension were unknown. The hypothesis tested in this retrospective study was that operative relief of left ventricular outflow tract obstruction resulted in a substantial reduction in pulmonary artery pressures and mitral regurgitation without necessitating mitral valve replacement. Patients were included if their preoperative pulmonary systolic pressure was greater than 35 mm Hg and if they were without concomitant cardiac disease, with the exception of mitral regurgitation. Since 1962, 49 patients who fit our criteria underwent left ventricular myotomy and myectomy with 98% follow-up. Mean follow-up was 7.9 +/- 0.7 (mean +/- standard error of the mean) years with a range of 0.8 to 18.4 years. Early hospital mortality rate was 12% (n = 6); two deaths from low cardiac output and four from arrhythmia. There were 43 (88%) hospital survivors and 18 late deaths. Actuarial survival rate after operation was 87% +/- 5% (n = 31) at 5 years and 55% +/- 8% (n = 9) at 10 years. Thirty-nine of 43 survivors (91%) returned 9 +/- 1 months postoperatively for follow-up evaluation including cardiac catheterization. The majority (83%) were in New York Heart Association functional class I or II postoperatively. Cardiac catheterizations indicated a fall in pulmonary arterial systolic pressure from 62 +/- 3 (range = 36 to 105) to 38 +/- 2 (range = 21 to 65) mm Hg (p = 0.0001) with no difference in right atrial pressure or cardiac output. Pulmonary arterial wedge mean pressure decreased from 24 +/- 1 to 16 +/- 5 mm Hg (p = 0.0002) and preoperative mitral regurgitation improved or was abolished in 85% of patients studied (n = 13). Rest and maximal provocable left ventricular outflow tract gradients decreased from 81 +/- 7 and 103 +/- 5 to 14 +/- 3 and 45 +/- 8 mm Hg, respectively (p = 0.0001). Comparison of the above-mentioned patients, operated on since 1982, with a preoperatively matched group who underwent mitral valve replacement in the same interval showed no statistically significant difference in mortality, morbidity, hemodynamic outcome, or functional outcome with a mean follow-up of 2 years. We conclude that a consistent, significant reduction (mean = 40%) in preoperative pulmonary arterial systolic pressure, clinical symptoms, and mitral regurgitation occurs with relief of outflow tract obstruction by left ventricular myotomy and myectomy and that pulmonary hypertension and mitral regurgitation are not indications for mitral valve replacement in these patients.

Blood Pressure↗
PubMed1989

Methylene blue for neutralization of heparin.

Patients with protamine allergy present a difficult dilemma when reversal of heparin is required for excessive bleeding. Premedication with steroids and antihistamines has not been shown to effectively prevent anaphylactic reactions in patients with hypersensitivity to protamine. Other heparin antagonists are either not available or are too toxic for human use. This report describes a patient in whom methylene blue was used effectively to neutralize heparin and decrease bleeding due to heparinization. In vitro testing was then done to further define the interaction of heparin and methylene blue. This testing demonstrated that methylene blue neutralized heparin levels of 1 u/ml as well as 10 u/ml. Methylene blue acted as an anticoagulant when present at levels of 3000 micrograms/ml. However, it acted as a coagulant when present in intermediate levels of 800 micrograms/ml and 1600 micrograms/ml. The plasma levels necessary for neutralization of heparin levels of 1 unit/ml (the levels achieved in patient therapeutically anticoagulated) are easily achieved using doses routinely used in treatment of methemoglobinemia. Although the toxicity of methylene blue has been well defined at the lower doses of 2-4 mg/Kg, work still needs to be done to determine safety of the drug at the higher doses necessary to neutralize heparin levels achieved in bypass patients.

Adult↗
PubMed1989

Effect of left ventricular septal myectomy on concurrent mitral regurgitation.

To assess the impact of left ventricular septal myectomy (Morrow procedure) performed for obstructive hypertrophic subaortic stenosis on co-existing mitral regurgitation, we examined the preoperative and postoperative left ventriculograms of 35 patients (13 of them women) who underwent left ventricular septal myectomy alone or with concomitant operation. The mean age was 45 +/- 3 years (range, 19 to 74 years). Patients underwent left ventriculography at an average of 15 +/- 3 months postoperatively (range, 1 to 78 months). Severity of mitral regurgitation was evaluated by two teams of reviewers. Mitral regurgitation due to catheter entrapment or to premature ventricular contraction or other arrhythmia was excluded. Overall, 51% of patients showed improvement in the severity of mitral regurgitation, and all those with more severe mitral regurgitation (ie, 3+) demonstrated improvement. The population was subdivided for analysis into those with coronary artery disease requiring bypass grafting at the time of left ventricular septal myectomy (n = 7, 20%) and those without coronary artery bypass grafting. Among the 7 patients undergoing bypass grafting, 71% demonstrated improvement in the degree of mitral regurgitation as compared with only 46% of those without bypass grafting (p less than 0.005 by X2 analysis). Significant reductions in peak gradients at rest and in response to provocation, and in New York Heart Association functional class, also occurred in both groups.

Adult↗
PubMed1989

Clinical and hemodynamic results after mitral valve replacement in patients with obstructive hypertrophic cardiomyopathy.

Mitral valve replacement has been performed in patients with obstructive hypertrophic cardiomyopathy if: (1) the interventricular septum is smaller than 18 mm in the region of usual resection; (2) atypical septal morphology is encountered; (3) a previous left ventricular myomectomy has been performed but residual major obstruction and symptoms persist; or (4) intrinsic mitral valve disease exists. Since 1983, mitral valve replacement has been performed in 58 patients with obstructive HCM only. Thirty-three female patients (mean age, 47.9 years) and 25 men (mean age, 45.7 years) met criteria 1 through 3 for mitral valve replacement. Patients with intrinsic mitral valve disease (criterion 4) were omitted from this study. All patients were in New York Heart Association functional class III or IV and had failed optimal medical therapy. Low-profile mechanical prostheses and bioprostheses were implanted, and the early mortality (less than 30 days or in the hospital) was 8.6% (5/58). Six patients (11.3%) died late, 3 suddenly of probably arrhythmia, 2 of respiratory failure, and 1 of an anticoagulant-related complication. After mitral valve replacement, 40 (83%) of 48 patients surviving operation and returning for evaluation were in functional class I or II, whereas 8 patients were in functional class III. Hemodynamic data obtained 6 months postoperatively showed that pulmonary artery wedge pressure was normal (13.7 +/- 4 mm Hg [+/- standard deviation]), left ventricular end-diastolic pressure had decreased (10.9 +/- 3.4 mm Hg), cardiac index was maintained (2.6 +/- 0.6 L/min/m2), and resting and provoked gradients were unremarkable. Mean follow-up was 24.2 months, actuarial survival was 86% at 3 years, and survival free from thromboembolism, anticoagulant-related complication, reoperation, and congestive heart failure for the same interval was 68%. Complications such as ventricular septal defect and complete heart block are avoided in patients undergoing mitral valve replacement, but device-related and cardiac-related complications can add to the morbidity and mortality in these patients in the long term.

Adult↗
PubMed1989

Enhanced regional left ventricular function after distant coronary bypass by means of improved collateral blood flow.

To determine whether coronary artery bypass surgery can improve function in left ventricular regions not amenable to direct revascularization, 24 patients with multivessel coronary artery disease were studied by radionuclide angiography and coronary arteriography before and 6 months after coronary artery bypass surgery. All had proximal stenosis of the left circumflex artery or a major obtuse marginal branch. Left ventricular regional function was assessed by dividing the left ventricular region of interest into 20 sectors; the 8 sectors corresponding to the posterolateral free wall were used to assess function in the left circumflex artery distribution. Change in function in the left anterior descending territory was not analyzed because of the non-specific septal hypokinesia that develops postoperatively. For the total group, coronary artery bypass surgery significantly increased both global left ventricular ejection fraction during exercise (43 +/- 13% to 50 +/- 14%, p less than 0.001) and the change in ejection fraction from rest to exercise (-7 +/- 10% to 0 +/- 6%, p less than 0.001). Such improvement was observed in 9 of 10 patients with all stenoses bypassed, and to an equivalent degree in 9 of 10 patients in whom the left circumflex artery either could not be bypassed or the bypass graft was occluded (but bypass grafts to other coronary arteries were patent). Similarly, regional ejection fraction in posterolateral segments during exercise also increased comparably after operation in patients with a patent (from 57 +/- 18% to 70 +/- 19%, p less than 0.001) or nonpatent (from 51 +/- 14% to 68 +/- 14%, p less than 0.001) left circumflex graft.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Results of operation for coexistent obstructive hypertrophic cardiomyopathy and coronary artery disease.

This study describes the operative management and outcome of 28 patients with obstructive hypertrophic cardiomyopathy and hemodynamically significant coronary artery disease. Each patient underwent coronary artery bypass grafting and concomitant left ventricular myotomy-myectomy or mitral valve replacement. The mean age at operation was 59 years (range 42 to 74). Five patients (18%) died as a result of operation, four in the immediate postoperative period and one at 2 months postoperatively. Three patients died after the immediate postoperative period of causes unrelated to the operation. The mean follow-up period for the 20 currently surviving patients was 4.8 years (range 4 months to 10.8 years). Nineteen of these patients have experienced substantial functional improvement; all are currently asymptomatic or only mildly symptomatic. Twenty-one patients underwent cardiac catheterization before and after operation; each experienced relief of left ventricular outflow tract obstruction after operation. Twelve patients had a preoperative outflow gradient greater than or equal to 50 mm Hg (average 86 +/- 7) under basal conditions, which decreased to 3 +/- 1.8 mm Hg postoperatively (p less than 0.001). Nine patients had a severe preoperative gradient only with a provocative maneuver (average 93 +/- 6 mm Hg), which decreased to 24 +/- 8 mm Hg postoperatively (p less than 0.001). Five of the 24 patients undergoing left ventricular myotomy-myectomy incurred an iatrogenic ventricular septal defect. This operative complication occurred primarily in patients with a relatively thin ventricular septum (less than 20 mm) and contributed importantly to postoperative death in two of the patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Amiodarone-induced complications after cardiac operation for obstructive hypertrophic cardiomyopathy.

The occurrence of unanticipated and seemingly unexplicable major complications of hepatic, pulmonary, and cardiac dysfunction after palliative operation for obstructive hypertrophic cardiomyopathy prompted a review of 71 sequential patients. Fifty-five patients had been treated preoperatively with beta-blockers, calcium-channel inhibitors, or both, and 16 had received amiodarone for six to 566 days (mean time, 210 days) at total doses ranging from 8 to 175 g (mean dose, 82 g) and had drug-free intervals prior to operation of zero to 457 days (mean time, 91 days). Comparisons were made between the two treatment groups and between those with and without major complications within the amiodarone-treated group. Preoperative cardiac studies, sex, age, functional class, and type of operation were not related to outcome for the entire patient cohort. In amiodarone-treated patients, the major findings were as follows: a 50% incidence of hepatic dysfunction with a tenfold increase in concentrations of serum glutamic-oxaloacetic transaminase and serum glutamic-pyruvic transaminase; a 25% incidence of pulmonary dysfunction necessitating a fourfold increase in the number of days of ventilator support; and a 19% incidence of low cardiac output syndrome with two deaths. Only 44% of the amiodarone-treated group had no serious complications. The incidence of major complications of the liver, lungs, and heart was 2%, 0%, and 2%, respectively, in patients not treated with amiodarone. Abnormal preoperative pulmonary function studies were predictive of prolonged postoperative ventilatory support. Discontinuation of amiodarone for several months prior to operation appeared to reduce the incidence of major complications. The necessary drug-free interval required preoperatively could not be determined from this retrospective experience.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Effect of surgical reduction of left ventricular outflow obstruction on hemodynamics, coronary flow, and myocardial metabolism in hypertrophic cardiomyopathy.

To assess the impact of operative reduction of left ventricular outflow obstruction in hypertrophic cardiomyopathy, measurements of great cardiac vein flow, oxygen and lactate content, left ventricular pressures, and cardiac index were measured at rest and during pacing stress in 20 consecutive patients (13, myotomy-myectomy; six, mitral valve replacement; one, both myotomy-myectomy and mitral valve replacement) who underwent both preoperative and postoperative studies. All had angiographically normal epicardial coronary arteries. Operation resulted in reduction in outflow gradient (64 +/- 38 to 4 +/- 7 mm Hg, p less than 0.001) and in left ventricular systolic pressure (186 +/- 32 to 128 +/- 22 mm Hg, p less than 0.001) and was associated with reduction in great cardiac vein flow (101 +/- 26 to 78 +/- 16 ml/min, p less than 0.001) and oxygen consumption in the anterior left ventricle and septum (11.9 +/- 4.1 to 8.4 +/- 1.9 ml O2/min, p less than 0.001) in the basal state. During rapid atrial pacing, 13 of 20 patients experienced chest pain postoperatively, whereas all 20 developed chest pain during preoperative pacing, with an improvement in pacing anginal threshold (or heart rate 150 if no chest pain was experienced) of 16 +/- 18 beats/min (p less than 0.001). The peak great cardiac vein flow (161 +/- 41 to 131 +/- 45 ml/min, p less than 0.025) and myocardial oxygen consumption (19.4 +/- 6.1 to 14.3 +/- 5.5 ml O2/min, p less than 0.005) during pacing, which correlated directly with the severity of the basal left ventricular gradient (p = 0.011 and p = 0.002, respectively), were also reduced by surgery. Lactate metabolism during pacing changed from net production before surgery to net consumption after operation (-17 +/- 47.6 to 4.4 +/- 29.8 mumol/min, p less than 0.01), with six of 20 patients producing lactate after surgery compared with 13 of 20 before surgery (p = 0.06). The six patients with the highest peak great cardiac vein flow (greater than 175 ml/min) during preoperative pacing had greater symptom and metabolic benefit during pacing after surgery compared with the 14 patients with lower peak coronary flow. Postpacing left ventricular end-diastolic pressure (30 +/- 7 to 23 +/- 7 mm Hg, p less than 0.001) and pulmonary artery wedge pressure (24 +/- 6 to 20 +/- 5, p less than 0.001) were reduced after surgery.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1988

The effect of coronary artery bypass grafting on left ventricular systolic function at rest: evidence for preoperative subclinical myocardial ischemia.

Successful coronary artery bypass grafting (CABG) improves exercise-induced left ventricular (LV) dysfunction in patients with coronary artery disease (CAD), but its potential for improving resting LV function remains controversial. To assess the influence of CABG on LV function at rest, 31 CAD patients without previous myocardial infarction were studied before and 6 months after CABG by radionuclide angiography after all cardiac medicines were withdrawn. No patient had angina or ischemic electrocardiographic changes at rest. In 27 patients with patent bypass grafts, CABG significantly increased LV ejection fraction during exercise (47 +/- 11% before to 63 +/- 9% after operation, p less than 0.001), indicating reduction in exercise-induced LV ischemia. Moreover, LV ejection fraction at rest also increased (55 +/- 9 to 60 +/- 8%, p less than 0.001), with 20 of 27 patients manifesting an increase compared with preoperative values. Eleven of these 20 patients had apparently normal LV function at rest (ejection fraction and regional wall motion) before CABG. LV regional ejection fraction was computed by dividing the LV region of interest into 20 sectors. Regional analysis indicated that improved ejection fraction at rest after CABG occurred in regions developing ischemia during exercise before CABG. In 4 patients with occluded grafts, the ejection fraction at rest was unchanged by CABG globally (59 +/- 8 to 58 +/- 9%, difference not significant) and regionally. Thus, LV global and regional function at rest improved after successful CABG, even in patients with normal global LV ejection fraction and no visually detectable wall motion abnormality before surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Long-term serial changes in left ventricular function and reversal of ventricular dilatation after valve replacement for chronic aortic regurgitation.

In most patients with aortic regurgitation, valve replacement results in reduction in left ventricular dilatation and an increase in ejection fraction. To determine the relation between serial changes in ventricular dilatation and changes in ejection fraction, we studied 61 patients with chronic severe aortic regurgitation by echocardiography and radionuclide angiography before, 6-8 months after, and 3-7 years after aortic valve replacement. Between preoperative and early postoperative studies, left ventricular end-diastolic dimension decreased (from 75 +/- 6 to 56 +/- 9 mm, p less than 0.001), peak systolic wall stress decreased (from 247 +/- 50 to 163 +/- 42 dynes x 10(3)/cm2), and ejection fraction increased (from 43 +/- 9% to 51 +/- 16%, p less than 0.001). Between early and late postoperative studies, diastolic dimension and peak systolic wall stress did not change, but ejection fraction increased further (to 56 +/- 19%, p less than 0.001). The increase in ejection fraction correlated with magnitude of reduction in diastolic dimension between preoperative and early postoperative studies (r = 0.63), between early and late postoperative studies (r = 0.54), and between preoperative and late postoperative studies (r = 0.69). Late increases in ejection fraction usually represented the continuation of an initial increase occurring early after operation. Thus, short-term and long-term improvement in left ventricular systolic function after operation is related significantly to the early reduction in left ventricular dilatation arising from correction of left ventricular volume overload. Moreover, late improvement in ejection fraction occurs commonly in patients with an early increase in ejection fraction after valve replacement but is unlikely to occur in patients with no change in ejection fraction during the first 6 months after operation.

Adult↗