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Biomedical subjects

C R Conti

Publications and source records attributed to C R Conti.

At least 253 records · Page 14Linked to original sources
PubMed1985

Reproducibility of left ventricular area and volume measurements using a computer endocardial edge-detection algorithm in normal subjects.

The variability of serially recorded 2-dimensional echocardiograms in normal subjects was determined. During a 2-week period, 10 normal subjects underwent echocardiography 5 times, in 2 laboratories, with use of different ultrasonographs. The video recordings were analyzed using a computer image analysis system (Quantic 1200) to provide standardized left ventricular short-axis areas and area ejection fraction (EF). Left ventricular volumes and volume EF were calculated. The 95% confidence limits of the percent difference for end-diastolic area and volume between 2 samples in a given subject were +/- 16.8 and +/- 16.7%, respectively. The limits for end-systolic area and volume were +/- 15.8 and +/- 17.0%, respectively. The 95% confidence limits for differences of area and volume EF between 2 recordings were +/- 12.8 and +/- 9.7%, respectively. No correlation was found between clinical grade (image quality) and the variability of area measurements. A good correlation (r = 0.98) was found between area and volume EF for any given subject over the 5 observations. These confidence limits are narrower than those previously recorded.

Adult↗
PubMed1985

The healing process in normal canine arteries and in atherosclerotic monkey arteries after transluminal laser irradiation.

To evaluate the healing response of both normal and atherosclerotic arteries to laser radiation, 7 mongrel dogs and 4 hypercholesterolemic atherosclerotic monkeys underwent catheterization with a right Judkins catheter-optical fiber system designed to maximize arterial wall injury. Argon laser radiation was then delivered to the abdominal aorta and iliofemoral arteries. In the 11 animals, a total of 917 sites were irradiated in 33 arteries. Angiography did not reveal dissection or aneurysm formation; occlusive thrombosis was found in 2 arteries. Perforation of the arterial wall was a frequent complication. In animals killed between 1 hour and 4 days, light and electron microscopy of lased sites showed craters filled with a coagulum of blood and cellular debris with only a few adherent platelets. Healing occurred with a minimal inflammatory response and involved both fibroblasts and smooth muscle cells. Reendothelialization was seen in all animals killed between 7 and 14 days after lasing and was complete by 30 to 60 days. Within this period, no accelerated atherosclerosis was seen at lased sites in the hypercholesterolemic monkeys. It is concluded that transluminal lasing of normal arteries in dogs and in atherosclerotic arteries of monkeys is followed by healing and reendothelialization within a few weeks.

Angiography↗
PubMed1985

Coronary hemodynamic responses during spontaneous angina in patients with and patients without coronary artery spasm.

The mechanisms of spontaneous angina were evaluated during cardiac catheterization in 13 patients who had angina occurring without provocation at rest. Left ventricular and systemic hemodynamics, coronary venous flows (thermodilution technique), electrocardiogram and coronary angiograms were recorded before and during spontaneous angina. Angiography during spontaneous angina showed that 5 patients had coronary spasm (group I) and 8 patients did not (group II). In group II there was a preponderance of multivessel coronary artery disease. Left ventricular end-diastolic pressure increased in all patients in both groups during spontaneous angina. In group I, 4 patients had transient ST elevation and 1 patient had peaked T waves during angina. Transient ST depression occurred during spontaneous angina in all group II patients. Group I patients had decreased coronary sinus flow (4 of 5 patients) or decreased regional flow (5 of 5) during spontaneous angina. Coronary resistance and ratio of double product to coronary blood flow increased in all patients. In group II, coronary hemodynamic responses during spontaneous angina varied. Coronary venous flows, coronary resistance and ratio of double product to coronary blood flow showed no uniform pattern. Thus, patients with severe coronary artery disease can have spontaneous angina without angiographic findings of coronary spasm. After analysis of angiograms and coronary hemodynamics in these patients, no apparent uniform mechanism for spontaneous angina was found.

Aged↗
PubMed1985

A comparative study of laser beam characteristics in blood and saline media.

Little information is available concerning the influences on laser radiation exerted by the various media through which lasing is done. The effects of saline solution and blood on argon laser beam divergence and projection were studied. In addition, the resulting effects on arterial tissue were evaluated after lasing through these media. This was performed with the fiber tip held in various positions relative to the arterial wall. The presence of blood, even in a diluted form, increased beam divergence and reduced forward projection. Perpendicular lasing through saline solution resulted in crater diameters similar in size to the core diameter of the fiber used irrespective of energy levels (424 +/- 97 microns at energy = 2 W X 5 seconds and 490 +/- 80 microns at energy = 2 W X 10 seconds). In contrast, lasing through blood produced much wider craters that increased in size with the higher energy level (878 +/- 215 microns at 2 W X 5 seconds and 1,294 +/- 314 microns at 2 W X 10 seconds). Arterial wall damage could also be inflicted at a greater distance when lasing through blood than through saline solution. Lasing arterial tissue through blood with the fiber tip held parallel to and in contact with the arterial wall resulted in wide craters when lasing was performed in a "static" as well as a "dynamic" fashion. Lasing through saline solution in these positions produced no visible damage to the arterial wall. These results provide some guidelines that may be useful in the clinical application of Argon laser revascularization.

Arteries↗
PubMed1985

Effects of age on ventricular-vascular coupling.

The effects of age on the interrelation between the physical properties of the arterial tree (aortic input impedance) and left ventricular performance (cardiac output) were studied in 45 subjects, aged 19 to 62 years, without apparent cardiovascular disease. Ascending aortic pulsatile pressure and blood flow velocity were measured with a multisensor catheter and cardiac output by green dye or the Fick method. Heart rate and end-diastolic aortic pressure remained unchanged with age, whereas aortic systolic, mean and pulse pressures and aortic radius increased. In subjects younger than 30 years, early systolic pressure usually exceeded late systolic pressure (type C beat); in subjects older than 50 years, late systolic pressure usually exceeded early systolic pressure (type A beat). In 55% of subjects aged 30 to 50 years, early and late systolic pressures were essentially equal (type B beat). The impedance spectra from all subjects showed fluctuations about the characteristic impedance (index of elastance) that were greater in the older subjects. Peripheral resistance increased 37% (r = 0.47, p less than 0.001) over the age range of 20 to 60 years, whereas characteristic impedance increased 137% (r = 0.66, p less than 0.001). The fundamental impedance modulus increased, and the impedance modulus minimum shifted to a higher frequency. These changes in the impedance spectral pattern indicate that the ascending aorta becomes stiffer and the cross section of the peripheral vascular bed decreases with age, causing increased pulse wave velocity and wave reflection.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Large vessel coronary vasospasm: diagnosis, natural history and treatment.

The diagnosis of coronary artery spasm is confirmed by angiography, for example, change in caliber of the coronary arteries plus evidence of ischemia. The prevalence and contribution of coronary artery spasm in the individual patient with symptoms of ischemic heart disease is not known and depends on how the condition is defined. The prognosis of patients with coronary artery spasm appears to depend on the presence or absence of severe coronary atherosclerosis, that is, those with severe disease have a worse prognosis. Nitrates should be used to initiate therapy in all patients with this problem. Intravenous nitrates have proven useful in patients whose symptoms are difficult to control and who require hospitalization. beta blockers used alone may be detrimental in patients with coronary artery spasm, but studies supporting the detrimental effects are few. The combination of nitrates, beta blockers and nifedipine has proved effective therapy for many patients with recurrent angina at rest, possibly related to coronary artery spasm. Several open-label and double-blind placebo control trials have shown that all of the calcium antagonists are effective short-term agents for patients with proven coronary artery spasm. When nifedipine was compared with isosorbide dinitrate in a randomized crossover, double-blind trial in patients with coronary artery spasm, both drugs were shown to be efficacious and neither was superior. The traditional alpha-blocking agents have not been shown to be an effective therapy, but a recent study of prazosin, a selective alpha blocker, revealed excellent results in patients whose conditions were resistant to therapy with traditional calcium blockers, beta blockers and, in 1 case, phenoxybenzamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1985

"Hot tip": another method of laser vascular recanalization.

UNLABELLED: This study is a preliminary report evaluating the use of laser radiation to heat a metal-capped fiber for arterial recanalization. The method was compared to the currently used bare-ended fiber for recanalization of occluded vessels. The model used was a human coronary artery xenograft transplanted in the femoral artery of the dog. At 4 weeks following the transplantation, laser recanalization was attempted using the heated metal probe ("hot tip") in five arteries and the bare fiber in another five arteries. RESULTS: 1) Angiography demonstrated recanalization in all five arteries treated with the "hot tip" and three of the five arteries treated with the bare fiber. 2) Only one perforation occurred with the "hot tip," whereas three perforations occurred with the bare fiber. 3) The larger metal cap was capable of creating a wider channel in the occluded arterial segment. Although the trend favored the heated metal cap in terms of recanalization and less perforation than the bare fiber, the total number of experiments were not adequate to demonstrate statistical significance. Microscopic examination of the vessels recanalized by either technique was similar. Characteristic charring at the recanalization site was seen regardless of the technique used. These observations suggest that the effect of direct laser radiation on plaques is predominantly a thermal effect. Although these results would suggest utilization of a metal-capped fiber for vascular recanalization, more studies need to be done to confirm these preliminary findings.

Animals↗
PubMed1985

Isosorbide dinitrate and nifedipine in variant angina pectoris.

The efficacy of isosorbide dinitrate (ISDN) in variant angina is enhanced by the addition of a calcium antagonist. A prospective double-blind, crossover trial of ISDN, 40 to 120 mg/day, and nifedipine, 40 to 120 mg/day, in 19 patients with variant angina and various degrees of coronary atherosclerosis showed that although both agents were equally effective in controlling angina of vasospastic origin, some patients responded better to one or the other drug. Such response could not be predicted by demographic factors, ECG changes, or degree of coronary atherosclerosis. Since quantitative angiography done in a similar group of patients showed that intracoronary nitroglycerin, 200 micrograms, was a more potent vasodilator than sublingual nifedipine, 10 mg (p less than 0.01), the calcium antagonists may have a different mechanism of preventing variant angina attacks and may act in an additive or synergistic fashion when administered in combination with long-acting nitrates. Such a combination will increase coronary blood flow, reduce ventricular volume and end-diastolic pressure, and reduce systemic arterial resistance. Coronary vasospasm may be directly prevented by a general inhibition of smooth muscle contraction by the calcium antagonist. Clinical studies suggest that combination therapy significantly improves the long-term prognosis of patients with variant angina and reduces the need for bypass surgery. Thus combining ISDN with a calcium antagonist is a rational and effective treatment for variant angina.

Angina Pectoris, Variant↗
PubMed1985

Mortality, morbidity, and cost-accounting related to coronary artery bypass graft surgery in the elderly.

The purpose of this study was to document early mortality, perioperative complication rate, duration of hospitalization, and costs related to coronary artery bypass graft (CABG) surgery in the elderly. Arbitrarily, elderly patients were defined by age greater than or equal to 65 years; younger patients were less than or equal to 60 years old. A detailed list of specific perioperative complications was analyzed. Early (30-day) mortality was similar between groups, while 120-day mortality was higher among elderly compared with younger patients (7.6% versus 1.3%; p = 0.05). The number of elderly patients with 1 or more complications was also higher than among the younger patients (62% versus 43%; p = 0.05). When the incidences of atrial arrhythmias and transient psychoses were considered minor complications and excluded from consideration, the incidence of major complications was higher in the elderly: 41 major events among 76 younger surviving patients compared with 89 major complications in 61 older surviving patients (p = 0.001). Time spent in the intensive care unit and the duration of postoperative hospitalization were also greater in the elderly (p = 0.01 and p = 0.001, respectively). Finally, the elderly group incurred greater costs than the younger patients (p = 0.03). The likelihood of increased perioperative morbidity in elderly patients is documented in this study. Also, it appears that the increased frequency of complications in elderly patients is associated with a longer hospital stay and greater financial expense. Consequently, the careful preoperative evaluation of these patients, including cautious patient selection, assumes greater importance. After CABG procedures, the highly symptomatic elderly patient may experience dramatic relief of symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1985

In vitro effects of argon laser radiation on blood: quantitative and morphologic analysis.

Use of the argon laser to recanalize stenosed arteries may require delivery of the beam through blood. To assess the degree of hemolysis and debris formation, 84 samples of citrated whole blood were exposed to argon laser radiation with varying power (1, 2 and 3 watts) and duration (5, 10, 20 and 40 seconds). Compared with control samples, only blood samples exposed to a power of 3 watts for 40 seconds showed a marked decrease in hematocrit (from 37 +/- 1.3 to 33 +/- 1.4%, p less than 0.01) and a marked increase in both free hemoglobin concentration (from 0.2 +/- 0.2 to 1.3 +/- 0.5 g/100 ml, p less than 0.01) and debris weight (from 0.9 +/- 0.3 to 2.8 +/- 0.5 mg, p less than 0.01). Scanning electron microscopy of debris from samples of whole blood, washed erythrocytes and platelet-rich plasma lased at 3 watts for 40 seconds documented the presence of membrane denaturation of blood elements, resulting in their fusion to form complex mesh-like conglomerates. Similar morphologic changes were observed in whole blood samples exposed to a "hot tip" rather than laser radiation. These data indicate that: 1) argon laser radiation with a power of 3 watts does not produce apparent hemolysis or debris formation for exposure periods up to 20 seconds, and 2) the effects of laser radiation on blood are probably mediated by thermal denaturation of cell membranes, as suggested by the same morphologic changes produced by thermal injury from a "hot tip."

Argon↗
PubMed1985

Effect of nifedipine on coronary hemodynamics in patients with left anterior descending coronary occlusion.

The mechanisms responsible for the beneficial effects of calcium channel antagonists in patients with effort angina were investigated by studying the coronary hemodynamic responses of the anterior left ventricular region before and after administration of nifedipine in 13 patients whose left anterior descending coronary artery was filled by flow from collateral vessels. Nifedipine was given bucally in a dose (10 or 20 mg) that decreased aortic pressure 5 mm Hg or more. Nifedipine increased collateral flow (regional thermodilution) in only three patients (p = NS), but consistently decreased coronary resistance in the left ventricular anterior region (p less than 0.05). Anterior region myocardial oxygen consumption did not change after nifedipine administration. Lactate metabolism was evaluated in eight patients: values were abnormal in four patients before nifedipine; after nifedipine, values remained abnormal in three of these patients and became abnormal in one other. During atrial pacing stress, angina occurred in all patients before nifedipine and at the same or lower heart rate in nine patients after nifedipine. After nifedipine administered at the same rate that induced angina during the control period, collateral flow and myocardial oxygen consumption were usually lower (both p less than 0.05), but anterior region coronary resistance was unchanged compared with control values. Lactate metabolism was not usually improved. Thus, although nifedipine maintained collateral flow while aortic pressure decreased, no consistent beneficial effect on pacing-induced angina was seen.

Adult↗
PubMed1985

Reduction in blood flow in normal and narrowed coronary arteries of dogs by leukotriene C4.

The hemodynamic effects of intracoronary leukotriene C4 (0.3 to 10.0 micrograms) in seven anesthetized dogs with normal and severely narrowed coronary arteries were examined. Intracoronary leukotriene C4 caused a significant dose-related reduction in coronary blood flow in both normal and narrowed coronary arteries with no effect on heart rate or mean arterial pressure. However, left ventricular end-diastolic pressure increased at the 10.0 micrograms dose. The reduction of blood flow in normal and narrowed coronary arteries in response to leukotriene C4 was similar. At the peak effects of leukotriene C4, there was evidence of intracoronary thromboxane A2 release. To examine the contribution of thromboxane A2 release to the coronary vasoconstrictor effects of leukotriene C4, dogs were administered leukotriene C4 after indomethacin pretreatment. The decrease in coronary blood flow was not significantly affected by pretreatment of the animals with indomethacin. However, indomethacin lowered baseline levels of thromboxane B2 and blocked the release of thromboxane A2 after leukotriene C4 administration. Thus, intracoronary leukotriene C4 causes direct dose-dependent decrease in coronary blood flow of similar magnitude in both normal and narrowed coronary arteries. These coronary hemodynamic effects of leukotriene C4 in dogs are not mediated by release of thromboxane A2. Leukotriene C4 released from activated leukocyte in the intracoronary thrombus or in the injured myocardium may reduce coronary blood flow and adversely influence the fate of the affected myocardial tissue.

Animals↗
PubMed1985

Laser recanalization of acutely thrombosed coronary arteries in live dogs: early results.

Laser recanalization was attempted in thrombosed coronary arteries of 10 dogs. In all dogs a coronary thrombus was obtained by passing a low grade electrical current through a guide wire advanced into the artery. Recanalization was then attempted using an argon laser with energy levels ranging from 3 to 30 J. In six dogs a 140 micron core optical fiber was positioned proximal to the thrombus and lasing was done during fiber advancement. The thrombosed artery was recanalized in one dog, perforated in four and neither recanalized nor perforated in one. In the remaining four dogs a steerable guide wire was advanced across the thrombus and a catheter was passed over the guide wire and exchanged for a 200 micron core optical fiber. After fiber withdrawal, mechanical recanalization without lasing was performed in one of the four dogs. In the remaining three dogs, both the fiber and the catheter were again advanced distal to the thrombus and lasing was done during withdrawal; this caused coronary perforation in all dogs. Laser recanalization of thrombosed coronary arteries in dogs using currently available techniques is feasible but results in a very high incidence of perforation.

Acute Disease↗
PubMed1985

Regional coronary hemodynamic responses during the cold pressor test: lack of effect of nitroglycerin.

The effects of large coronary vessel dilation on responses to immersion of a hand and forearm in ice water for 1 minute (that is, the cold pressor test) were calculated for 17 patients. Regional coronary blood flow and aortic and left ventricular pressures were continuously measured before and during two cold pressor tests, each performed before and after administration of sublingual (0.4 mg) or low dose intracoronary (0.01 mg) nitroglycerin. During the initial cold pressor test, heart rate and coronary pressures increased in all patients; total and regional coronary resistance usually increased in patients with severe coronary artery disease and usually decreased in patients with a normal coronary angiogram. Sublingual nitroglycerin induced important systemic effects, but intracoronary nitroglycerin did not; both induced dilation of coronary arteries viewed angiographically. Regardless of the route of nitroglycerin administration, coronary hemodynamic responses were directionally similar during the repeat cold pressor test compared with the initial one. These data support the concept that changes in tone of the large coronary arteries are not important in producing the cardiac responses observed during the cold pressor test.

Adult↗
PubMed1985

Nitrate therapy for ischaemic heart disease.

The beneficial effects on nitrates are related to a combination of coronary and non-coronary effects of the drugs. Patients with different forms of ischaemic heart disease may respond differently. For instance, in a patient with rest angina due to coronary artery spasm, nitrates will reverse or prevent coronary artery spasm. In contrast, the patient with severe coronary artery stenosis and reproducible angina during exercise, may obtain relief because nitrates decrease venous return, left ventricular size and left ventricular pressure, thus decreasing myocardial oxygen demands. Nitrates can be used to treat patients with chronic angina, unstable angina and myocardial infarction. In patients with chronic angina, oral nitrate preparations with sustained-release action have been shown to decrease the indices of myocardial oxygen demand for up to 12 h. In patients with unstable angina, intravenous nitrates usually relieve symptoms in patients refractory to oral therapy. In patients with acute myocardial infarction, early administration with intravenous nitrates may benefit patients as suggested by randomized prospective trials. Nitrate tolerance and nitrate dependence does not seem to be an important clinical problem. Perhaps this is related to the way the drug is given, i.e. intermittently. In some instances, however, when high doses are used or the drug is administered intravenously or by the transdermal route, constant levels of nitroglycerine may be attained and the patients may develop tolerance. Although nitrates are effective drugs, it is native to think that they will be used alone to manage the complex problems associated with ischaemic heart disease. Other than hypotension and adverse effects of the drug, there seems to be no contraindication to the combination of nitrates with calcium antagonists or beta blockers.

Angina Pectoris↗
PubMed1985

Calcium antagonists.

At present nitrates remain the initial treatment for relief or prevention of angina in patients with coronary artery disease. In cases where nitrates and beta blockers have been used and are ineffective for managing effort angina, calcium antagonists may be substituted or added to the beta-blocking treatment. When the predominant symptom is rest angina, and there is evidence suggesting coronary artery spasm, nitrates and a calcium antagonist can be effective therapy. In patients with heart block, bradyarrhythmias, heart failure, or hypertension nifedipine may be the drug of choice. In contrast verapamil merits choice when supraventricular tachycardia is present. Diltiazem appears intermediate between nifedipine and verapamil and may be particularly useful when hypotension or other side effects must be avoided.

Adrenergic beta-Antagonists↗