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Biomedical subjects

C R Conti

Publications and source records attributed to C R Conti.

At least 289 records · Page 16Linked to original sources
PubMed1983

Effect of glyceryl trinitrate on coronary and systemic hemodynamics in man.

The effects of sublingual and intracoronary nitrates on coronary artery diameter were evaluated in five separate experiments in man. The first three are concerned with sublingual nitrates and the last two with intracoronary nitrates. The data obtained indicate that (1) administration of a fixed dose sublingual nitrate results in an increase in percent coronary artery stenosis compared with control measurements; (2) small doses of sublingual nitrates can dilate coronary arteries without a significant reduction in systemic arterial pressure or increase in heart rate; (3) the magnitude of percent coronary artery dilation after a fixed dose of sublingual nitrate is inversely related to the size of the coronary artery, that is, the smaller the coronary artery diameter the greater the relative dilation after administration of sublingual nitrate; (4) fixed dose sublingual nitrate often dilated coronary stenoses, but the more narrow stenoses were less likely to dilate; (5) the optimal dose of intracoronary nitrate required to produce maximal or near maximal coronary dilation without clinically important systemic hemodynamic effects is in the range of 200 micrograms; (6) intracoronary nitrate is a more potent coronary artery dilator than sublingual nifedipine, when administered as a 10 mg dose.

Administration, Oral↗
PubMed1983

Influence of aortic stenosis on the hemodynamic importance of coronary artery narrowing in dogs without left ventricular hypertrophy.

Coronary hemodynamic effects of controlled left ventricular outflow obstruction stimulating aortic valve stenosis were studied in 20 open-chest dogs, with and without graded coronary artery diameter narrowing. Aortic stenosis was regulated so that a mean left ventricular-aortic pressure gradient of 46 +/- 20 mm Hg (mean +/- standard deviation) was created as both heart rate and stroke volume were unchanged. In addition, during aortic stenosis, mean aortic pressure (105 +/- 17 to 84 +/- 15 mm Hg, p less than 0.05) and diastolic pressure time index/systolic pressure time index ratio (1.2 +/- 0.3 to 0.6 +/- 0.2, p less than 0.05) decreased and end-diastolic left ventricular pressure (7 +/- 4 to 14 +/- 6 mm Hg, p less than 0.05) increased. With no coronary narrowing, mean coronary flow increased during aortic stenosis (53 +/- 23 to 62 +/- 23 ml/min) as the percentage of diastolic flow increased (83 +/- 6 to 89 +/- 4) and endocardial/epicardial ratio decreased (1.14 +/- 0.16 to 0.95 +/- 0.24) (all p less than 0.05). Peak reactive hyperemic flow also decreased (168 +/- 85 to 125 +/- 73 ml/min, p less than 0.05). This value with no coronary narrowing was similar to peak hyperemic flow with 60% narrowing without aortic stenosis. With 90% coronary narrowing, mean coronary flow decreased with or without aortic stenosis. Transmural flow distribution also decreased but was lower during aortic stenosis (0.86 +/- 0.19 to 0.61 +/- 0.25, respectively; p less than 0.05). These data suggest that although mean coronary flow is increased during aortic stenosis, endocardial flow may be limited, and coronary reserve exposed during reactive hyperemia appears decreased. When a coronary artery is narrowed, aortic stenosis has an even more important hemodynamic influence on the coronary circulation.

Acute Disease↗
PubMed1983

Quantitative coronary angiography during intracoronary streptokinase in acute myocardial infarction: how long to continue thrombolytic therapy?

An intracoronary infusion of streptokinase is often administered in patients with acute myocardial infarction. To address the question of how long intracoronary streptokinase should be infused, we studied 13 patients with symptoms and electrocardiographic findings suggesting an evolving myocardial infarction. We used subselective catheterization techniques and made quantitative angiographic measurements of the percentage of reduction of coronary artery (CA) diameter before intracoronary streptokinase therapy, immediately after reperfusion was established, and at the completion of streptokinase infusion. Before intracoronary streptokinase and after intracoronary nitroglycerin, nine patients had 100% obstruction of the CA in the "infarct-related vessel." In seven patients reperfusion was established (25 +/- 21 min, mean +/- SD) at which time CA diameter was reduced by 77 +/- 22%. The streptokinase infusion was then continued until repeated films (every 10 to 15 min) suggested no further change at the site of CA obstruction (93 +/- 68 min). The percentage of CA diameter reduction when streptokinase infusion was discontinued was 55 +/- 32%; this value was less (P less than 0.05) than that observed early after reperfusion. These data show that after initial reperfusion was achieved by the use of intracoronary streptokinase, additional streptokinase lessened the reduction of CA diameter. Residual thrombus may be present at the narrowed CA site early after reperfusion, and further "cleanup" can be achieved by prolonging streptokinase infusion.

Adult↗
PubMed1983

Comparison of the effects of nitroprusside and nitroglycerin on coronary size.

Nitroglycerin and nitroprusside are known to differ in their relative degree of systemic arterial and venous dilation. Nitroglycerin has been shown to be a potent large-vessel coronary dilator, but the effects of nitroprusside on coronary artery size are unclear. Accordingly, we studied coronary artery angiographic responses to both nitroprusside and nitroglycerin in 12 patients. Diameters Of left coronary artery segments were measured by quantitative angiography before and during an intravenous infusion of nitroprusside and after sublingual nitroglycerin when both drugs were administered in doses adjusted to achieve reductions in aortic pressure. Dilation of the left coronary artery was observed after nitroprusside and after nitroglycerin. Degrees of dilation were similar in the various left coronary artery segments after either nitroprusside or nitroglycerin. In general, segments located more proximally dilated less than those located more distally after either agent. We conclude that both nitroprusside and nitroglycerin are potent dilators of large epicardial and of smaller intramuscular coronary artery segments. The magnitude of dilation of all measured left coronary artery segments appeared remarkably similar with nitroprusside and nitroglycerin given in doses that produced a similar reduction in aortic pressure.

Angiography↗
PubMed1983

Electrocardiographic changes with coronary artery spasm.

The presence or absence of important ECG changes (e.g., ST elevation or depression greater than or equal to 1 mm) was evaluated in 79 consecutive patients with coronary artery spasm. In eight of these patients ECG changes usually did not accompany episodes of rest angina. Evaluation before, during, and after cardiac catheterization included multiple ECGs and ambulatory monitoring during angina. Our observations suggest that the ECG may not always be a sensitive indicator of coronary spasm. Thus the diagnosis of transient myocardial ischemia secondary to coronary spasm should not necessarily be excluded because of a lack of ECG changes during rest angina.

Aged↗
PubMed1983

Clinical outcome after treatment of rest angina with calcium blockers: comparative experience during the initial year of therapy with diltiazem, nifedipine, and verapamil.

The clinical outcome after the initial year of therapy with either diltiazem (D), nifedipine (N), or verapamil (V) was examined in 45 patients with rest angina. Age, frequency of angina, duration of symptoms, and ejection fraction were similar in all three treatment groups. Coronary artery disease was present in 60% of patients (5 of 13 given D, 8 of 16 given N, and 14 of 16 given V). Coronary spasm was suspected (ST elevation with angina) or documented (angiographically) in 35 (78%) patients. Twenty-nine (64%) patients had greater than 50% decrease in angina without a coronary event (9 taking D, 11 taking N, and 9 taking V). Coronary events (sudden death, infarction, and hospitalization for unacceptable angina control or bypass surgery) occurred in 13 (29%) patients (two taking D, four taking N, and seven taking V). To achieve these responses, 20 (44%) patients required additional antianginal drugs (long-acting nitrates, beta blockers, or other calcium blockers). Four of these 20 patients were taking D, nine were taking N, and seven were taking V. Seventeen (38%) patients experienced a side effect (none taking D, 6 taking N, and 11 taking V). Although rest angina can be controlled in the majority of patients during the initial year of treatment with calcium blockers, additional therapy is often required. Furthermore, the clinical course of patients presenting with rest angina remains unpredictable, even during calcium blocker treatment. Morbid events continue to occur, related in part to the extent of coronary artery disease.

Adult↗
PubMed1983

Long-term responses to nifedipine in patients with coronary spasm who have an initial favorable response.

Twenty-six patients with angina and coronary spasm participated in a randomized crossover trial comparing nifedipine with isosorbide dinitrate. Eighteen patients had a short-term beneficial response to nifedipine, and 14 of these were followed up for an average period of 9.4 months. During follow-up study, nifedipine was the primary therapy in these 14 patients, but other drugs were added when clinically necessary to control angina. There was an overall 86% beneficial response rate (greater than 50% decrease in angina frequency). However, 2 patients had a large increase (greater than 10 times) and 4 patients had a slight increase (transient) in angina frequency over the long term compared with the short-term response. The other 8 patients had a similar angina frequency compared with the short-term response. Of the 12 patients with a good response (transient slight increase or no change), 8 (67%) required additional drug therapy to maintain angina control. Nifedipine was discontinued in 2, and the dose was decreased in 3 of the 14 patients because of adverse effects. Three patients had a marked increase in angina at 9, 14, and 3 months, requiring hospitalization; 1 patient had coronary bypass for symptom control. Thus, patients with coronary spasm selected because of a favorable short-term response to nifedipine were effectively treated over the long term with nifedipine; however, additional therapy was often needed to control symptoms. Adverse effects were common, but simple reduction of nifedipine dose usually diminished the unwanted effects of the drug.

Angina Pectoris↗
PubMed1983

Coronary arterial aneurysm formation after balloon angioplasty.

The mechanism of coronary stenosis dilatation by percutaneous transluminal coronary angioplasty (PTCA) is incompletely understood. Five men who developed coronary arterial aneurysms at the site of PTCA are described. All patients were in New York Heart Association functional class III or IV at the time of PTCA. In 2 patients acute myocardial infarction was evolving and both had acute coronary occlusion. The other 3 patients had angiographic evidence of intimal disruption or acute coronary reocclusion as a result of PTCA, one of whom had undergone emergency coronary artery bypass grafting. Three patients received intracoronary streptokinase during PTCA. One patient was asymptomatic and 4 were symptomatic when the aneurysms were identified between 11 days and 4 months after PTCA. Other than the complex course and anatomy of these patients before and immediately after PTCA, no other features distinguished them from others undergoing this procedure.

Aged↗
PubMed1983

Influence of acute aortic insufficiency on the hemodynamic importance of a coronary artery narrowing. II. Various magnitudes of aortic insufficiency.

Coronary hemodynamic effects of controlled acute aortic insufficiency were studied in 40 open chest dogs with and without graded coronary diameter narrowing. An adjustable basket device was used to regulate aortic insufficiency, creating three groups: group 1, mild to moderate aortic insufficiency (regurgitant fraction less than 50%); group 2, moderately severe aortic insufficiency (regurgitant fraction greater than 50%); and group 3, aortic insufficiency with mean aortic pressure restored to control levels. Mean coronary blood flow was similar to control values in group 1, but was higher in groups 2 and 3. The endocardial/epicardial flow ratio was similar with and without aortic insufficiency. With graded coronary narrowing greater than 80%, coronary flow and endocardial/epicardial flow ratio decreased with or without aortic insufficiency. However, endocardial/epicardial flow ratio usually decreased more during aortic insufficiency. Peak reactive hyperemic flow after release of a 10 second coronary occlusion also decreased during aortic insufficiency. The amount of decrease compared with control values was related to the magnitude of aortic insufficiency. This value with no coronary narrowing in group 1 was similar to peak reactive hyperemic flow with a 60% coronary narrowing during the control period. In group 2, peak reactive hyperemic flow was similar to that with an 80% coronary narrowing during the control period. Restoring mean aortic pressure to control values in group 3 did not restore peak reactive hyperemic flow to control values. These data suggest that coronary flow reserve assessed with coronary narrowings or during reactive hyperemia is decreased during aortic insufficiency. The decrease in coronary flow reserve was more pronounced as the magnitude of aortic insufficiency increased.

Animals↗
PubMed1983

Regional coronary venous flow responses to transient coronary artery occlusion in human beings.

Coronary hemodynamic responses to transient coronary artery occlusion in 21 patients were investigated by using regional coronary venous thermodilution to measure regional coronary venous flows. Transient coronary artery occlusion was produced by coronary artery spasm (13 patients) or balloon inflation during coronary angioplasty (8 patients). The left anterior descending coronary artery was transiently occluded in 12 patients, the right coronary artery in 8 patients and the left circumflex artery in 1 patient. During transient coronary occlusion, regional venous flow decreased in 20 of the 21 patients (79 +/- 31 to 53 +/- 29 ml/min, mean +/- standard deviation [SD]; probability [p] less than 0.05) corresponding to the left ventricular region perfused by the occluded artery. Regional coronary resistance increased in all 21 of these regions (1.42 +/- 0.75 to 2.26 +/- 1.45 mm Hg/ml per min, p less than 0.05). Simultaneously measured blood flow and resistance in the left ventricular region supplied by the nonoccluded arteries did not change significantly (62 +/- 27 to 64 +/- 29 ml/min and 1.85 +/- 0.93 to 1.81 +/- 0.98 mm Hg/ml per min, respectively). Coronary hemodynamic changes were similar during transient coronary occlusion, whether produced by coronary spasm or by balloon inflation. However, the presence of angina, reversible electrocardiographic abnormalities and an increase of the left ventricular filling pressure were more common during coronary spasm (p less than 0.05 for all). Regional coronary hemodynamic changes during transient occlusion of the anterior descending, circumflex or right coronary artery were similar. These data show that coronary occlusion decreases regional left ventricular flow in the region perfused by the affected artery. The method of coronary occlusion or the coronary artery affected during occlusion did not seem to elicit different responses.

Adult↗
PubMed1983

Comparison of early and long-term results with intraoperative transluminal balloon catheter dilatation and coronary artery bypass grafting.

Twenty-six patients with chronic stable angina underwent intraoperative coronary artery balloon catheter dilatation and concomitant coronary artery bypass grafting (CABG). In one patient (3.8%) the catheter could not be passed through the arterial narrowing, and in two patients (8%) early angiographic evidence for arterial damage was detected. Postoperative angiographic data were available in 85% of patients early (mean 10 days) and in 50% of patients late (mean 12 months). Early results showed one perioperative myocardial infarction, 100% relief of angina, and no operative mortality. Compared to preoperative studies, of 23 angiographically visualized distal narrowings dilated in an antegrade fashion, 12 (52%) were unchanged, two (9%) were worse, and nine (39%) were improved. Those arterial segments with discrete distal narrowings (n = 13) had better angiographic results than those with diffuse distal narrowings (n = 9). In 49% of the former and in 22% of the latter arterial narrowings, improvement (increased luminal diameter) was documented postoperatively. In addition, there were four proximal narrowings which were dilated in a retrograde fashion; three were unchanged and one was improved compared to preoperative studies. Only one of 27 dilated segments (3%) was totally occluded postoperatively. Late results showed two patients (8%) developed recurrent chest pain and one patient (4%) died related to congestive heart failure. The two patients who had angiographically documented coronary arterial intimal injury showed evidence of resolution at late study. In 13 distal narrowings, six (46%) were unchanged, three (23%) were worse, and four (31%) were improved compared to the preoperative appearance. In 10 distal narrowings visualized both early and late postoperatively, nine were unchanged and one was worse. In summary, coronary artery balloon catheter dilatation during CABG is relatively safe and is associated with acceptable clinical results. Angiographic evidence for improvement is less than symptomatic relief postoperatively. Therefore, objective evaluation may be necessary for accurate determination of operative results. The need for a national registry related to intraoperative angioplasty is probably warranted.

Angina Pectoris↗
PubMed1982

Short- and long-term responses to diltiazem in patients with variant angina.

Short- and long-term effects of diltiazem on angina frequency were studied in 12 patients with variant angina (pain at rest with S-T elevation). Each patient first entered a double-blind short-term trial. Either diltiazem, in two dosage schedules (120 and 240 mg/day), or placebo was administered in a randomized double-blind program over 10 weeks. Significant decreases in frequency of angina were observed when diltiazem treatment periods were compared with placebo periods. Six patients were asymptomatic, one had 50 percent or greater decrease, and two had a smaller decrease in angina frequency. Two patients showed no important improvement during short-term diltiazem therapy. One patient experienced ventricular fibrillation in the placebo period and was advanced to treatment with open label diltiazem before responses could be ascertained in the double-blind trial. All other patients were then advanced to open label diltiazem therapy and followed up for an average of 16 months (range 8 to 23). Responses during the short-term trial accurately predicted responses during long-term therapy. Of the six patients who were asymptomatic during short-term therapy, five remained asymptomatic and one had rare episodes of angina. One other patient continued to have a good response (50 percent or greater decrease in angina frequency) and two other patients had a partial response. The two patients who did not respond during short-term therapy did not respond during long-term therapy.

Adult↗