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Biomedical subjects

A G Morrow

Publications and source records attributed to A G Morrow.

At least 19 recordsLinked to original sources
PubMed1979

Prosthetic aortic valves. Indications for and results of reoperation.

During a 15-year period from January 1962 through December 1976, 42 patients who had undergone a previous aortic valve replacement underwent reoperation. The mean interval between operations was 4.4 years. The indications for reoperation were aortic regurgitation resulting from mechanical malfunction (12 patients), ball variance (15 patients), perivalvular leaks (five patients), prosthetic stenosis (eight patients), anemia (one patient), and recurrent emboli (one patient). The indications were characteristic of a specific valve series. The most common reoperation was aortic valve replacement (29/42), which had a 10.3% operative mortality. Poppet change (10/42) carried a 10% operative mortality and no operative deaths followed suture closure of perivalvular leaks. Eighty-eight percent of patients alive six months after reoperation were New York Heart Association functional class 1 or 2. At last follow-up, 95% of surviving patients were still functional class 1 or 2, with a mean cumulative survival of 4.7 years after reoperation. This experience demonstrates that those patients surviving long enough to undergo reoperation can expect a reasonable operative risk, long-term survival, and excellent clinical improvement.

Anemia↗
PubMed1979

Exercise performance after septal myotomy and myectomy in patients with obstructive hypertrophic cardiomyopathy.

The effect of left ventriculomyotomy and myectomy on exercise capacity and cardiac function in patients with obstructive hypertrophic cardiomyopathy has not previously been determined. In this study, 29 patients were evaluated during graded treadmill exercise before and after operation. Postoperatively, 27 of 29 patients reported symptomatic improvement and had greatly reduced left ventricular outflow gradient. Twenty-five of 28 patients (89 percent) attained higher exercise levels after operation, and this was accompanied by an increase in total body oxygen consumption from 16 to 21 ml/min per kg (P less than 0.005). A significant increase in cardiac index during maximal exercise also accompanied this improved exercise performance (5.0 to 5.7 liters/min per m2, P less than 0.05). The increase in maximal cardiac index was associated with greater desaturation of mixed venous blood (34 to 24 percent, P less than 0.02) in patients with preoperative angina. At a given level of mixed venous oxygen saturation (30 percent), overall mean cardiac index was higher postoperatively (4.6 to 5.2 liters/min per m2, P less than 0.05). These results suggest that, although several mechanisms probably contribute to symptomatic improvement after myotomy and myectomy, enhanced cardiac performance plays an important role in the majority of patients.

Adolescent↗
PubMed1979

Left ventricular function at rest and during exercise after aortic valve replacement in patients with aortic regurgitation.

To determine the effect of aortic valve replacement on reversing abnormalities of left ventricular function in patients with aortic regurgitation, radionuclide cineangiography was used to study 16 sympatomatic patients with aortic regurgitation before and 6 months after aortic valve replacement. Before operation, left ventricular ejection fraction was 46 +/- 3 percent at rest (normal mean +/- standard error of the mean 57 +/- 1 percent; P less than 0.001), and decreased to 37 +/- 4 percent during exercise (normal 71 +/- 2 percent; P less than 0.001). after operation, ejection fraction rose to 58 +/- 4 percent at rest, indistinguishable from the normal value, and during exercise was 53 +/- 4 percent, increased (P less than 0.001) from before operation but significantly (P less than 0.001) subnormal. Thus, aortic valve replacement can improve but usually does not normalize left ventricular function during exercise in symptomatic patients with aortic regurgitation.

Adult↗
PubMed1979

Hemodynamic effects of various modes of cardiac pacing after operation for idiopathic hypertrophic subaortic stenosis.

The hemodynamic effects of varying heart rate and pacing site were studied in 6 patients with idiopathic hypertrophic subaortic stenosis following operative relief of outflow obstruction. Ventricular pacing (117 beats per minute) resulted in a 26% decrease in cardiac output (p less than 0.02), a 54% increase in pulmonary capillary wedge pressure (p less than 0.03), and a 23% decrease in mean blood pressure (p less than 0.05), compared with normal sinus rhythm (88 beats per minute). Slow atrial pacing (112 beats per minute) did not significantly alter any hemodynamic variable compared with normal sinus rhythm. Rapid atrial pacing (143 beats per minute) produced a similar degree of hemodynamic impairment as ventricular pacing. This study demonstrates that ventricular pacing at heart rates commonly used clinically and rapid atrial rates result in a significant fall in cardiac output. Preservation of atrial systole at heart rates that allow adequate diastolic ventricular filling of a hypertrophied, noncompliant ventricle is stressed. In addition, atrial electrodes are useful to record atrial electrograms or induce rapid atrial stimulation to treat supraventricular tachyarrhythmias.

Adult↗
PubMed1979

Congenital cardiac abnormalities in monozygotic twins. Report and review of the literature.

A pair of monozygotic twin girls is reported with concordance for 3 congenital cardiac abnormalities: (1) secundum atrial septal defect, (2) aneurysm of the membraneous ventricular septum, and (3) electrocardiographic frontal plane left axis deviation. A review of the published materials shows a 9.5 per cent incidence of concordance for congenital heart disease among monozygotic twins. In those in whom a precise cardiological diagnosis was made, 15/16 pairs (95%) were concordant for a specific defect, 2 had an additional defect, and only 1 pair had completely dissimilar defects. Concordance for congenital heart disease in monozygotic twins is uncommon, but when it occurs the defects will most often be identical.

Child↗
PubMed1979

Effect of septal myotomy and myectomy on left ventricular systolic function at rest and during exercise in patients with IHSS.

Patients with idiopathic hypertrophic subaortic stenosis (IHSS) have supernormal left ventricular systolic function at rest. Septal myotomy/myectomy reduces outflow obstruction and symptoms. However, it has been proposed that operation causes myocardial damage, with consequent reduction in left ventricular function and potentially deleterious long-term consequences, despite relief of symptoms. To evaluate the effect of myotomy and mylectomy on left ventricular function, we employed noninvasive radionuclide cineangiography at rest and during maximal exercise in21 consecutive patients with IHSS, before and 6 months after operation. In 30 normal subjects, the ejection fraction (EF) was 57 +/- 2% at rest and 71 +/- 2% during exercise. Before operation in patients with IHSS, the EF was supernormal at rest (76 +/- 2%, p less than 0.001), and normal during exercise (71 +/- 3%, NS). All patients improved from NYHA functional class III-IV preoperatively to class I-II postoperatively; the maximal provocable gradient invariably diminished (average, 100 +/- , mm Hg preop, 33 +/- 9 mm Hg postop, p less than 0.001). Postoperatively, the EF at rest was 67 +/- 2%, still supernormal, but less than that noted preoperatively (p less than 0.001). During exercise, the EF was 66 +/- 4%, only mildly diminished (p less than 0.01) from that preoperatively. We conclude that muscle resection during myotomy and myectomy usually does not cause any important impairment of global left ventricular function at rest or during exercise stress.

Adolescent↗
PubMed1979

Selective arterialization of the coronary venous system. Encouraging long-term flow evaluation utilizing radioactive microspheres.

The long-term effectiveness of a retrograde coronary venous bypass graft (CVBG) to an ischemic left ventricle was evaluated in 18 dogs. A saphenous vein was interposed between the aorta and left anterior descending (LAD) vein. The LAD vein was ligated cephalad to the CVBG to prevent an arteriovenous fistula. The LAD artery was ligated at its origin to create anterior wall ischemia. Operative graft flow averaged 53 ml. per minute. The 14 surviving dogs were catheterized 3 to 5 months later. Ten of the 14 CVBG's were patent angiographically. The chests were opened and graft flow now averaged 50 ml. per minute. 141Ce microspheres were injected into the left atrium to measure myocardial flow to the anterior wall. In the 10 dogs with patent grafts, transmural flow was 39 +/- 1 (S.E.M.) ml. per 100 Gm. of tissue per minute. The endocardial/epicardial flow ratio was 1.4/1, indicating that retrograde venous perfusion effectively delivered blood to the subendocardium. After ligation of the CVBG, microsphere measured flow dropped to 15 +/- 1 ml. per 100 Gm. per minute. In 15 control dogs, anterior wall flow was 100 +/- 3 ml. per 100 Gm. per minute, decreasing to 13 +/- 2 ml. 45 minutes after ligation of the LAD artery and vein. None of the eight control dogs with simple ligation of the LAD artery and vein survived more than 5 days. Histologic examination of the anterior wall of the left ventricle, the area served by the CVBG's for 3 to 5 months, disclosed no evidence of venous sclerosis or thrombosis and no evidence of interstitial edema or hemorrhage. Thus a CVBG permitted long-term survival in an otherwise nonviable anatomic preparation. Moreover, restoration of flow with a CVBG was effective because it perfused all layers of the myocardium, especially the subendocardium--the crucial layer of myocardial muscle.

Animals↗
PubMed1979

Evaluation of right atrial-pulmonary artery conduits for tricuspid atresia. Experimental study.

Blood flow through right atrial-pulmonary artery (RA-PA) conduits was investigated. Experiments were designed to evaluate the pumping function of the right atrium, effects of the atrial versus ventricular pacing site, the necessity of a valve within the conduit, and the effect of positive-pressure ventilation on conduit flow. Twenty foxhounds were subjected to silicone patch closure of 90 percent of the tricuspid valve orifices to create stenosis. Ten dogs successfully underwent RA-PA shunting with a conduit with paralled limbs, one containing a prosthetic valve. The proximal main pulmonary artery was ligated to ensure total diversion of blood via the conduit. Valved and nonvalved conduit flow was significantly correlated with right atrial pressure (RAP): r = 0.95, p less than 0.05; r = 0.98, p less than 0.01, respectively. There was no significant effect of increasing heart rate (p = 0.19), atrial versus ventricular rhythm (p = 0.28), or the presence of a valve (p = 0.63). Increasing tidal volume resulted in increasing tidal conduit flow (expiration-inspiration) (r = 1.0, p less than 0.01), but mean flow was unaffected. Therefore, RAP is the most important factor influencing conduit flow. The absence of a valve, ventricular rhythm, and tachycardia did not significantly alter flow in this acute experimental model.

Animals↗
PubMed1978

Abnormal right ventricular size and ventricular septal motion after atrial septal defect closure: etiology and functional significance.

Postoperative echocardiogram often demonstrate persistent right ventricular dilatation and paradoxic ventricular septal motion after repair of an atrial septal defect. To determine the prevalence, causes and significance of these echocardiographic abnormalities, 31 patients were studied with catheterization and echocardiography before and after repair of an atrial septal defect. Before operation, every patient manifested right ventricular dilatation, and all but one had abnormal septal motion. After operation, right ventricular dilatation was noted in 24 (77%) and abnormal septal motion in 21 (68%) patients despite the absence of residual left to right shunting in 30 (97%). These echocardiographic abnormalities could be correlated with age at operation and length of postoperative follow-up study but did not correlate with the degree of preoperative right ventricular enlargement or with shunt size or right ventricular pressure before or after operation. There was no associated functional deficit as demonstrated by the normal maximal oxygen consumption in all 13 patients who underwent treadmill exercise testing 5 to 38 months after operation; these patients included 9 with persistent right ventricular enlargement and abnormal septal motion.

Adolescent↗
PubMed1978

Ventricular pseudoaneurysm after transaortic septal myotomy for hypertrophic subaortic stenosis.

Clinical and morphological features are described in a man in whom a pseudoaneurysm arising from the ventricular septum developed after transaortic septotomy for hypertrophic subaortic stenosis. Pseudoaneurysm of the left ventricle or ventricular septum has not been described previously in a patient with hypertrophic cardiomyopathy in whom only the transaortic approach was utilized for septotomy or septectomy or both. In addition, no previous studies have reported pseudoaneurysm arising from the ventricular septum.

Aortic Valve↗
PubMed1978

Long-term clinical course and symptomatic status of patients after operation for hypertrophic subaortic stenosis.

Long-term results of operation for IHSS were reviewed in 124 patients operated upon between 1960 and 1975. Most patients improved symptomatically and manifested marked reduction in LV outflow gradient at rest postoperatively. However, ten (8%) patients died of causes related to operation, 14 (12%) had persistent or recurrent severe functional limitation, and 11 (9%) died up to 13 years postoperatively due to hypertrophic cardiomyopathy. Overall annual mortality rate was 3.5% and was 1.8% for late deaths alone. Of 11 late postoperative deaths, six were sudden and five were due to chronic heart failure. Atrial fibrillation was significantly more common in patients who died late postoperatively than in survivors. Nine of the 11 late deaths had associated medical problems that may have contributed to their outcome. In conclusion, long-lasting clinical improvement occurred in most patients who survived operation for IHSS. However, 12% of patients deteriorated clinically over the 5.2 year average follow-up, and there is continued, small annual mortality.

Adolescent↗
PubMed1978

Delayed cardiac tamponade associated with prophylactic anticoagulation in patients undergoing coronary bypass grafting. Early diagnosis with two-dimensional echocardiography.

Pericardial tamponade occurring late in the hospitalization of a patient who has undergone a heart operation can be life threatening. Recognition of this insidious, but treatable, complication is difficult. Three patients experienced delayed tamponade while receiving warfarin prophylactically following coronary arter bypass. Two-dimensional echocardiography was useful in recognizing the effusion (and thus aided the diagnosis of tamponade) in each patients. The question of whether prophylactic antiocagulatin should be employed for patients undergoing coronary artery bypass procedures is also considered in light of both the present experience and collected reports from the literature.

Adult↗
PubMed1977

Aortic valve replacement in the elderly. Encouraging postoperative clinical and hemodynamic results.

Seventy-three patients aged 60 and over and 277 patients under 60 years of age underwent isolated aortic valve replacement (AVR) for aortic stenosis, regurgitation, and mixed disease from 1966 through 1975. Cardiac catheterization was performed five to nine months following operation in 77% of these patients. Follow-up averaged 55 months per patient. The hospital mortality in the elderly group was 2.7%, compared to 5.8% in the younger group. The late cardiac mortality was 21% and 19%, respectively. There was significant improvement (P less than .001) in the left ventricular end-diastolic pressure, cardiac index, and functional class in each of the three disease groups in the younger as well as the elderly patients. More important, the magnitude of improvement in each of these variables in patients over and under 60 years of age was not significantly different. Increasing longevity will make cardiac operations more common in the older population. These findings indicate that AVR carries the same low risk and brings about a similar improvement in left ventricular pump function in patients older and younger than 60.

Aged↗
PubMed1977

Effects of operation on left atrial size and the occurence of atrial fibrillation in patients with hypertrophic subaortic stenosis.

The relation between left atrial size and atrial fibrillation was examined in 37 patients who had left ventriculomyotomy and myectomy at the National Heart and Lung Institute. Atrial fibrillation was present in 11 of 27 (41%) patients with an echocardiographically measured left atrial dimension greater than 45 mm. No patient with a left atrial dimension less than 45 mm had atrial fibrillation pre or postoperatively. Eleven of 13 patients less than 40 years of age with an abnormal preoperative left atrial dimension had a 10% or greater reduction in left atrial dimension postoperatively. A group of 21 patients 40 years of age or older had an abnormal left atrial dimension preoperatively, and no significant change postoperatively. These results indicate that left ventriculomyotomy and myectomy can produce a significant decrease in left atrial size in younger patients with idiopathic hypertrophic subaortic stenosis. It is hoped that the decrease in atrial size may reduce the risk of atrial fibrillation in these patients.

Adult↗