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Biomedical subjects

C R Conti

Publications and source records attributed to C R Conti.

At least 397 records · Page 22Linked to original sources
PubMed1978

Pulsatile flow characteristics of aortic valve porcine heterografts in man.

Pulsatile flow characteristics in the ascending aorta were examined in 14 patients 12 months after aortic valve replacement with the glutaraldehyde-fixed porcine aortic heterograft. Analysis of the velocity signals permitted measurement of peak velocity, maximal acceleration, stroke volume, and ejection time in addition to the standard measurement of systolic aortic valvar gradient. Angiographic techniques permitted visualization of a pattern of blood flow in the ascending aorta. Valvar aortic gradients were minimal, and, when the phasic ascending aortic blood flow velocity parameters were compared to those in a group of eight patients with normal aortic valves, these characteristics of flow were nearly indistinguishable. This remarkable similarity to the flow characteristics of normal valves may be important to long-term performance of a prosthetic aortic valve. Our results suggest that the glutaraldehyde-fixed porcine heterograft warrants serious consideration when selecting a substitute aortic valve for man.

Animals↗
PubMed1977

Input impedance of the systemic circulation in man.

To determine the systemic input impedance, pulsatile pressure and flow were measured in the ascending aorta in 16 human subjects who were undergoing diagnostic cardiac catheterization. Blood flow was measured with a catheter-tip electromagnetic velocity meter, and pressure with an external transducer connected with the fluid-filled lumen of the catheter. Five subjects were found to have no evidence of cardiovascular disease (group A, mean age 32 +/- 2 years, mean aortic pressure 97 +/- 4 mm Hg). Seven had clinical and angiographic signs of coronary arterial disease, and mean pressures less than 100 mm Hg (group B, mean age 48 +/- 2 years). Four subjects had signs of coronary disease and mean pressures greater than 100 mm Hg (group C, mean age 48 +/- 3 years). The frequency spectra of impedance were qualitatively similar in all three groups and resembled those previously observed in the canine aorta. Characteristic impedance was lower in the normal subjects (group A, average 53 dyn sec cm-5) than in the subjects with coronary artery disease (groups B and C, average 129 dyn sec cm-5). Among the subjects with coronary disease, characteristic impedance was higher in the hypertensive subjects (group C, average 202 dyn sec cm-5) than in those with lower mean pressures (group B, average 95 dyn sec cm-5). External left ventricular work per unit time (hydraulic power) averaged 1715 milliwatts (mW) in group A, 1120 mW in group B, and 2372 mW in group C. Cardiac outputs were within normal limits in all subjects, but tended to be lower in group B than in group C. These results suggest that the subjects of group C were better able to meet the increased energy demands imposed by an abnormally high aortic input impedance. Further investigation is needed to learn whether the high impedances in subjects with coronary disease represent an increase with age and transmural pressure alone, or whether some additional factor is involved. The data on relatively normal subjects permit a tentative definition of the normal limits for aortic input impedance in man: 26-80 dyn sec cm-5.

Adult↗
PubMed1976

Constrictive pericarditis.

Constrictive pericarditis, although still a relatively rare disease, continues to be a clinical problem that most practicing cardiologists may encounter. A major clinical clue to diagnosis is the continued elevation of the central venous pressure after adequate diuresis. The diagnosis is further supported by (1) prominent X and Y descents in the jugular venous pulse, (2) a relatively normal or only slightly enlarged cardiac silhouette in a patient with congestive heart failure, (3) pericardial calcification or significant congestive failure especially when the right sided signs predominate without obvious cause. When the disease is suspected, appropriate investigation should be undertaken using both the noninvasive and the catheterization studies. If the diagnosis is supported, then the choice of therapy at present is based primarily on severity of symptoms with surgical removal of the constricting pericardium being the therapy of choice in patients unable to be managed medically.

Adolescent↗
PubMed1975

The "angina-producing" myocardial segment: An approach to the interpretation of results of coronary bypass surgery.

The first 153 cases of saphenous vein aortocoronary bypass surgery performed at The Johns Hopkins Hospital were reviewed. Eighty-eight percent of the 140 late survivors reported significant symptomatic improvement. Seventy-one unselected patients consented to complete reevaluation at a mean interval of 6.1 months postoperatively. Vein bypass patency in this group was 66 percent. Eighty-two percent of these 71 patients had improved performance on electrocardiographic stress testing. There were no significant differences between hemodynamic status on pre- and postoperative studies regardless of the status of vein bypass patency. Repeat coronary angiography revealed a 30 percent incidence of new total occlusions of the intrinsic coronary circulation. Segmental wall motion on ventriculography was improved in 12 percent, unchanged in 50 percent and decreased in 38 percent of the segments analyzed. Localized electrocardiographic changes compatible with myocardial damage developed in the immediate postoperative period in 45 of these patients (63 percent); in 38 of the 45, these changes corresponded to new angiographic abnormalities. Physiologic mechanisms underlying symptomatic improvement were sought by identification of an "angina-producing" myocardial segment. In most instances, alleviation of angina could be related to either: (1) a patent bypass graft into an unchanged intrinsic coronary artery with presumed increased blood flow to the distal coronary segment, or (2) occlusion of the bypass graft and the corresponding coronary artery with probable infarction of previously ischemic myocardium. Current criteria for the selection of patients undergoing coronary bypass surgery are reviewed in the light of these findings. It is concluded that relief of disabling angina is the major indication for surgery. Prevention of myocardial infarction and improvement in left ventricular function are at present less reliable objectives.

Angina Pectoris↗