Search PubMed⌕ Search

Biomedical subjects

C R Conti

Publications and source records attributed to C R Conti.

At least 343 records · Page 19Linked to original sources
PubMed1980

Effects of transient regional ischemia on left ventricular diastolic function.

Simultaneous left ventricular echograms and high-gain pressure recordings were made during 30 s of regional myocardial ischemia induced by snare occlusions of the proximal left anterior descending (LAD) or left circumflex (LCx) coronary arteries in open-chest dogs. Left ventricular diastolic diameter (d) and pressure (p) were measured during slow filling. A normalized (for diameter D) distensibility estimate (DE = delta d/delta p/D) was calculated, as were slow filling slopes (SFSs) of the septum and posterior wall. After occlusion, significant (p less than 0.05) decreases of DE and anterior and posterior left-ventricular-wall mid-diastolic normalized slow-filling slopes (ASFS/D and PSFS/D) were observed. Correlations were noted between percentage decreases of DE and ASFS/D (r = 0.69, p less than 0.0001) and PSFS/D (r = 0.62, p less than 0.0001). No significant differences between decreases of DE and SFS were noted between ischemic and non-ischemic regions. Transient regional myocardial ischemia was associated with a generalized alteration in left ventricular filling patterns in mid-diastole.

Animals↗
PubMed1980

Platelet function studies in coronary artery disease. VII. Effect of aspirin and tachycardia stress on aortic and coronary venous blood.

The effects of orally administered aspirin (650 mg) on platelet aggregation patterns and counts in aortic and coronary venous blood were evaluated in patients with coronary artery disease. Studies were conducted at rest and during the stress of tachycardia. Before administration of aspirin, platelet aggregation and counts were lower (p less than 0.01) in coronary venous blood than in aortic blood. The stress of tachycardia resulted in increased (p less than 0.01) platelet aggregation only in coronary venous blood. After administration of aspirin, differences in platelet aggregation and counts between coronary venous and aortic blood at rest were eliminated, and the tachycardia-associated increase in coronary venous blood platelet aggregation was significantly reduced. These observations suggest that aspirin influences and abolishes the changes that occur in blood platelet function as platelets traverse the atherosclerotic myocardial vascular bed. The absence of an increase in platelet aggregation during the stress of tachycardia after administration of aspirin may have important pathophysiologic and therapeutic implications.

Adult↗
PubMed1980

Acute haemodynamic effects of oral prazosin in severe mitral regurgitation.

Acute haemodynamic effects of single dose oral prazosin were studied in eight patients with mitral regurgitation. Heart rate, mean systemic arterial pressure, pulmonary arterial pressure, left ventricular filling pressure, and forward cardiac output were measured in all patients. At peak effect, prazosin reduced mean systemic arterial pressure (95 +/- 4 to 86 +/- 4 mmHg), pulmonary arterial pressure (45 +/- 6 to 23 +/- 4 mmHg), and left ventricular filling pressure (30 +/- 4 to 21 +/- 3 mmHg). Pulmonary and systemic vascular resistance also fell (316 +/- 49 to 208 +/- 43 dynes s cm-5 and 2132 +/- 148 to 1491 +/- 94 dynes s cm-5, respectively). Forward cardiac index increased from 1.89 +/- 0.12 to 2.43 +/- 0.13 l/min per m2 and stroke volume from 43 +/- 5 to 57 +/- 6 ml/beat after prazosin. The onset of these changes occurred between 15 and 30 minutes, peaked between 45 and 60 minutes, and persisted for six hours. These data indicate that in patients with mitral regurgitation oral prazosin promptly improves cardiac performance (judged by increased forward cardiac output and reduced left ventricular filling pressure) as systemic and pulmonary vascular resistance are reduced.

Adult↗
PubMed1980

Detection and management of the asymptomatic patient with coronary artery disease.

A clinician is faced with several dilemmas when evaluating the asymptomatic individual. The first dilemma relates to 'who should be evaluated'. Generally the first step in evaluation is the exercise stress test (fig. 2). The following are guidelines that can be used to systematically evaluate the individual asymptomatic patient who presents with a 'positive exercise stress test' (fig. 3). An ambulatory ECG can be performed to evaluate the occurrence and frequency of asymptomatic ST segment depression and the response to nitrates. Isotope angiography and exercise 201Tl perfusion studies may provide additional information relating to the physiologic significance of asymptomatic ST segment depression. If these studies are negative and the patients' 'positive stress test' was obtained at a high cardiac workload coupled with rapid normalization of the ST segment after exercise, and there was no change in the ST segment depression after nitroglycerin, a reasonable case can be made to simply observe the patient. If the exercise test is 'positive' at a low cardiac workload, associated with prolonged ST segment depression and/or a 'positive' exercise thallium or positive exercise angiography, or there was change in the ST segment depression after nitroglycerin or a lifethreatening arrhythmia developed, coronary angiography seems warranted.

Aged↗
PubMed1980

Use of vasodilators in congestive heart failure.

In order to select the proper vasodilator agent for the treatment of congestive heart failure, the underlying etiology and pathophysiology of heart failure must be understood since they are important determinants of the response to the particular vasodilator being used. Short-term studies are impressive. Most patients respond dramatically to vasodilators. Long-term studies are not available at this time. When they become available, the clinical usefulness of this group of drugs will be put in proper perspective.

Cardiac Output↗
PubMed1980

Use of catheter-tip velocity--pressure transducer to evaluate left ventricular function in man: effects of intravenous propranolol.

A catheter-tip velocity transducer with two high-fidelity pressure manometers was used to evaluate the left ventricular (LV) hemodynamic effects of intravenous propranolol (10 mg). Nine patients without clinical evidence of heart failure were studied. Pulsatile ascending aortic blood flow velocity and pressure and LV pressure were measured continuously during drug administration. Beat-to-beat changes in stroke volume index, stroke work index, LV end-diastolic pressure, maximum blood flow velocity and acceleration, and maximum LV dP/dt were determined. Propranolol produced a decrease in maximum blood flow velocity (from 58 +/- 4.7 to 42 +/- 5.1 cm/sec, p less than 0.002), and acceleration (from 1181 +/- 130 to 847 +/- 117 cm/sec2, p less than 0.002, max dP/dt (from 1361 +/- 70 to 1146 +/- 63 mm Hg/sec, p less than 0.002), stroke volume index (from 47 +/- 3.0 to 38 +/- 3.2 ml/m2, p less than 0.002) and total stroke work index (from 702 +/- 33 to 603 +/- 44 mJ/m2 p less than 0.04), with little change in mean aortic pressure, peak systolic pressure and LV end-diastolic pressure. Depression in myocardial function was detectable within 1 minute after initiation of propranolol and persisted when negative chronotropic effects were eliminated by atrial pacing. The multisensor catheter technique allows rapid and safe detection of changes in cardiovascular function during propranolol administration in conscious man.

Adult↗
PubMed1980

Vascular load defined by the aortic input impedance spectrum.

The load that the arterial system places upon the myocardium during ventricular ejection is of primary importance in the consideration of ventricular function. This dynamic load can be characterized by the total aortic input impedance spectrum obtained from Fourier analysis of pulsatile pressure and flow waves recorded in the ascending aorta. Certain indices derived from the impedance spectrum provide quantitative and qualitative information about this dynamic load in terms of peripheral arteriolar dimensions (resistance), aortic wall stiffness (compliance), and wave reflections (reflectance). Studies in isolated heart preparations and intact dogs have shown that increases in resistance (decrease in arteriolar caliber) or aortic stiffness (decrease in aortic compliance) independently influence an increase in peak left ventricular pressure and a decrease in stroke volume. An increase in wave reflections also has the potential to reduce stroke volume while increasing peak pressure. Recent human studies have shown that in heart failure patients the components of the dynamic vascular load are also elevated compared to subjects without heart failure. Infusion of the vasodilator sodium nitroprusside abruptly reduces these components of vascular load as ventricular stroke output is enhanced. Thus, there is sufficient evidence to indicate that changes in the mechanical properties of the arterial tree influence the opposition to ventricular outflow. Since these properties can be described by the aortic input impedance spectrum, this function can be used to define the external load imposed on the ventricle by the vascular system.

Animals↗
PubMed1980

Effect of graded narrowing of left main coronary artery on left ventricular function.

The relationship between left ventricular function and coronary blood flow was studied in 16 chloralose-anesthetized dogs with an intact coronary circulation and left ventricle. Left ventricular dimensions, hemodynamic function indices, and coronary blood flow were measured simultaneously as the origin of the left coronary artery was narrowed by a calibrated snare. With a left coronary blood flow reduction of 17% (average), left ventricular minor axis diameter increased and maximum aortic blood flow acceleration and maximum rate of rise of left ventricular pressure decreased. Other measured indices of ventricular function did not change significantly. Larger coronary flow decrements caused a decrease in aortic systolic and diastolic pressures, stroke volume and cardiac output and an increase in heart rate and left ventricular end-diastolic pressure. These results confirm a close relationship between left ventricular function and blood supply.

Animals↗
PubMed1979

Intracardiac M-mode echocardiography for continuous left ventricular monitoring: method and potential application.

Because no accurate and readily applied method exists for continuous recording of left ventricular cavity dimensions and wall motion in man, we designed a catheter-mounted echocardiographic probe. The purpose of this report is to describe the instrumentation, technique, limitations, complications and preliminary observations employing the probe in humans. The echo transducer built into a cardiac allowed positioning in the right heart under fluoroscopy. The echo signals permitted continuous left ventricular cavity measurements at rest and during maneuvers. Our results suggest that intracardiac echo may be able to provide clear definition of motion patterns of the mitral valve and left ventricular walls. The ultrasonic catheter is an instrument that potentially offers a new technique for continuous monitoring of left ventricular size and motion.

Cardiac Catheterization↗