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Biomedical subjects

R H Helfant

Publications and source records attributed to R H Helfant.

At least 37 records · Page 2Linked to original sources
PubMed1988

The effect of changes in afterload on systolic bulging.

It has been previously shown that after acute coronary occlusion, the extent of systolic bulging is dependent on preload and the function of the remote nonischemic myocardium is influenced by the motion of the ischemic myocardium as well as by the loading conditions. To examine the isolated effects of changing afterload on the movement of acutely ischemic and nonischemic myocardium, seven open-chest, anesthetized dogs were paced from the left atrium at a rate of 100 beats/min after crushing of the sinus node. The pulmonary artery was perfused artificially and the left ventricular end-diastolic pressure (LVEDP) was carefully controlled with a right heart bypass system. Twenty minutes after occlusion of the left anterior descending artery, the peak left ventricular pressure (LVP) was adjusted to three levels (70, 90, and 110 mm Hg) by blood withdrawal or aortic constriction, while the LVEDP was kept constant (8.3 +/- 2.3 mm Hg). Segment length in the ischemic (IZ) and nonischemic zones (NZ) were measured with sonomicrometers and total, isovolumetric, and ejection systolic shortening (% delta L) were calculated. Changes in left ventricular minor-axis diameter were measured with diameter crystals. Increasing the peak LVP increased the LVP both at aortic valve opening and closing. To keep the LVEDP constant as peak LVP was increased, the cardiac output had to be decreased (p less than .0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Quantification of absolute luminal diameter by computer-analyzed digital subtraction angiography: an assessment in human coronary arteries.

Determination of absolute lumen diameters has been shown to be useful in predicting the functional importance of a coronary stenosis. In this study, both single-plane and orthogonal biplane digital subtraction angiograms were obtained in human cadaver coronary arteries. A single absolute diameter was calculated at the site of greatest narrowing in 20 segments by two automated computerized algorithms. Minimum and maximum diameters at the site of the stenosis were measured from pathologic sections prepared after pressure fixation. Method 1, which determines the edges by means of the first derivative of the videodensity curve, derived absolute diameters that fell between the pathologic minimum and maximum in 10 of 20 segments. Method 2, which determines the edges by an average of the first and second derivatives of the videodensity change, derived absolute diameters that fell between the pathologic minimum and maximum diameters in 15 of 20 segments. Method 1 correlated well with the maximum pathologic diameter (r = .76) and less well with the minrmum pathologic diameter (r = .67). Method 2 correlated very well with the maximum pathologic diameter (r = .79) and also correlated well with the minimum pathologic diameter (r = .74). As would be expected, the computerized algorithms tended to overestimate the minimum pathologic diameter and to underestimate the maximum pathologic diameter. In six segments, two orthogonal views were analyzed; no further accuracy was discernible over single-plane determinations. Thus quantitative coronary angiography by digital subtraction angiography is sufficiently accurate to be of use in the measurement of the severity of a coronary stenosis.

Coronary Angiography↗
PubMed1987

Prognosis of symptomatic coronary artery disease in young adults aged 40 years or less.

The clinical course and coronary angiographic features of symptomatic coronary artery disease (CAD) in patients younger than 40 years old are described with particular emphasis on the prevalence of myocardial infarction and the degree of diminished functional capacity. Eighty-five patients with CAD proven by coronary angiography were studied. There were 73 men and 12 women aged 27 to 40 years. Fifty-nine patients presented with acute myocardial infarction, most of whom denied previous chest pain, and 14% (12 patients) presented with less acute chest pain syndromes. Coronary angiography was performed in all patients, and greater than or equal to 70% luminal diameter narrowing was considered significant. Coronary angiographic findings reveal 51% with 1-vessel CAD, 31% with 2-vessel and 19% with 3-vessel. Subsequently, 23 patients had coronary artery bypass graft surgery, 7 underwent angioplasty and 55 were treated medically. Follow-up for a mean of 3 years revealed only 1 death and 4 subsequent hospital admissions for cardiac events. Fifty-three percent of the patients are entirely pain free, and only 4 (5%) have significant symptoms of angina pectoris. Although 15 (18%) are not employed regularly, the remainder work full- or part-time, or plan to work in the near future. These data suggest that the short-term prognosis and functional status of young patients with CAD is excellent.

Adult↗
PubMed1987

Assessment of coronary artery stenoses by digital subtraction angiography: a pathoanatomic validation.

Automated computer assessment of coronary stenoses from digital subtraction angiographic images comparing geometric and videodensitometric algorithms was performed. Digital subtraction angiograms were acquired on a 512 X 512 X 8 bit pixel matrix at 8 frames/second. Fifteen segments from nine human cadaver coronary arteries, with lesions ranging from 0% to 97%, were analyzed. Hand injections of radiopaque dye were made during the pulsatile infusion of saline solution at physiologic pressures and flows. Individual frames best demonstrating a lesion were digitally magnified and the stenosis was measured; the operator identified only the segment of interest. The artery was then injected with a rapidly hardening gel during the same rate of infusion as that used during image acquisition. Histologic sections were cut at 2 mm intervals after fixation and elastic stains applied. Photographs of the section comparable to the site determined from the angiogram were taken, and hand planimetry by a blinded investigator was performed. There was an excellent correlation between histopathology and videodensitometry (r = 0.93; p less than 0.0001). The two geometric algorithms studied also had very good correlations (r = 0.90 and 0.84) with pathology. Two experienced angiographers, despite excellent agreement with each other, had lower correlations with pathology than any of the three computer algorithms studied (r = 0.79 and 0.83, respectively), although this difference did not attain statistical significance. This in vitro model simulating in vivo conditions validates the use of automated videodensitometric and geometric computer algorithms to interpret coronary angiography and assess severity of stenosis.

Algorithms↗
PubMed1987

Thallium imaging with single photon emission computed tomography.

Evaluation of myocardial perfusion with thallium-201 SPECT has advantages over planar images. These advantages are related to better contrast of the images, lack of superimposition of normal and abnormal areas, and a three-dimensional representation of the site and extent of perfusion abnormalities (ischemia, scar, or both). For this reason, rotational tomography is superior to planar imaging in assessing the extent of coronary artery disease, in the detection of small infarcts, and for quantitative measurements. Several techniques have provided accurate quantitative data for infarct sizing both in animals and men. The ability to quantitate infarct size (or ischemia) will be extremely important in studies of myocardial salvage, risk stratification, and longitudinal studies to evaluate the effects of medical and surgical interventions.

Animals↗
PubMed1987

Improved survival with coronary bypass surgery in patients with three-vessel coronary disease and abnormal left ventricular function. Matched case-control study in patients with potentially operable disease.

Recent studies have suggested that patients with three-vessel coronary disease and abnormal left ventricular function have better survival rates with bypass surgery than with medical therapy alone. Case-control studies may give accurate survival estimates, but to be valid, selection biases must be taken into account. A matched case-control method was used to compare survival patterns in patients treated medically or surgically during the 1980s. Fifty medical patients with potentially operable coronary disease and 46 surgical patients were matched for significant three-vessel disease and abnormal ventricular function. These two groups had no significant differences with regard to 24 variables, including age (64 +/- 8 versus 63 +/- 10 years), chest pain class, congestive heart failure signs, ejection fraction (36 +/- 8 versus 37 +/- 9 percent), segmental wall score, or a coronary score evaluating lesion site and severity. There were slight differences between the two groups with regard to congestive heart failure symptoms (p = 0.04). Patients undergoing bypass surgery had improved four-year survival rates compared with the medical group (89 versus 55 percent; p = 0.01). Thus, this study used an effective case-control method to suggest that, in the 1980s, coronary surgery improves prognosis substantially in surgically approachable patients with severe coronary disease and ventricular dysfunction.

Aged↗
PubMed1987

Absence of coronary vascular reserve in myocardium distal to a fixed coronary stenosis.

In a study to test the hypothesis that vascular reserve is exhausted in the setting of a resting blood flow deficit, the left anterior descending or circumflex artery was cannulated and perfused from the left carotid artery. After reactive hyperaemia had been assessed a stenosis was produced with a screw clamp. In the first experiment a moderate stenosis (diastolic perfusion pressure 40 mmHg) was produced in the left anterior descending artery (three dogs) or left circumflex artery (three dogs). Blood pressure was held constant with aortic constriction during intracoronary adenosine infusion (6 mumol.min-1). The stenosis was then adjusted to the preadenosine perfusion pressure. In the second experiment the anterior interventricular coronary vein was also isolated and segment length crystals were placed in the ischaemic and non-ischaemic zones. Severe stenosis (flow reduction of at least 50% and evidence of decreased segmental shortening) was produced in the cannulated left anterior descending artery (eight dogs). Intracoronary adenosine was given with aortic pressure held constant by transfusion and coronary venous drainage. In the first experiment resting coronary flow (ml.min-1) decreased from 41(3) to 29(6) (p less than 0.05) with stenosis. Coronary flow increased from 29(6) to 34(7) (p less than 0.05) with adenosine and to 50(10) (p less than 0.05) with stenosis adjustment. Subendocardial flow (ml.g-1.min-1) decreased from 0.89(0.26) to 0.78(0.23) (p less than 0.05) with adenosine and then increased from 0.94(0.49) with perfusion pressure adjustment. Subepicardial flow tended to increase with adenosine, and increased further with stenosis adjustment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1987

Magnetic resonance imaging to evaluate patency of aortocoronary bypass grafts.

To assess the efficacy of magnetic resonance (MR) imaging in evaluating graft patency after coronary bypass surgery, 20 patients who had prior surgery (average 5.5 years, range 1.5 to 14) and recent cardiac catheterization because of chest pain were studied. No patient had surgical intervention or change in symptoms in the time interval between catheterization and MR imaging. These 20 patients had a total of 47 grafts, defined as proximal anastomoses: 20 to the left anterior descending or diagonal artery (LAD), 13 to the left circumflex artery marginal branches (LCX), and 14 to the right coronary artery or posterior descending artery (RCA). The patients underwent cardiac and respiratory gated MR scans in a 0.5 tesla magnet with an echo time of 22 msec and two repetitions in a 128 X 256 matrix. In-plane resolution was 2.7 mm. Every patient had a scan in the transaxial plane and some underwent scanning in the sagittal and coronal planes as well. A graft was considered patent by MR when a signal-free lumen was visualized in an anatomic position consistent with that of a bypass graft, had a lumen larger than the native vessels, was seen on more than one slice, and was seen at a level higher than that of the native vessels. If a known graft was not seen it was considered occluded. The scans were interpreted by consensus of two physicians aware of the operative but not the cardiac catheterization data.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Myocardial segment motion during regional ischemia--regional contraction and relaxation.

Several aspects of regional ischemic myocardial function determined by segment motion are discussed, based on our studies. Although global left ventricular function decreased progressively as the global severity of myocardial ischemia increased, there are several possible factors which may modify this relationship. As for the site of the ischemic area, occlusion of the left anterior descending artery resulted in a greater decrease in the left ventricular ejection fraction than occlusion of the left circumflex artery. Interaction between the ischemic myocardium and the non-ischemic myocardium may be a multifactorial phenomenon rather than simple tandem stretching. The segment length motion during acute ischemia appears to be complicated. The segment motion of the severe ischemic myocardium during systole and diastole was explained for the most part by a uniform tension-length curve which was independent of changes in the loading condition. This non-linear elastic property was fundamental to the production of segment motion asynchrony. The wall motion of the hypokinetic segment might be explained by a combination of the active change in myocardial stiffness and the non-linear elastic property of the myocardium.

Animals↗
PubMed1986

Medical and surgical survival in coronary artery disease in the 1980s.

The survival of 1,657 patients with angiographically proved coronary artery disease (CAD) was studied for 4 years (mean 2.0 +/- 1.2) during the 1980s to examine the prognostic importance of multiple clinical variables. One hundred of the 1,049 medically treated patients (9.5%) and 31 of the 608 surgically treated patients (5.1%) died. Multivariate analyses revealed that the strongest prognostic variables for survival in the medical group were indexes of left ventricular function (p less than 0.0001), severity of coronary stenoses (p less than 0.0001) and age (p = 0.005). However, only age (p less than 0.0001) was a significant prognostic variable in the surgically treated group. This study emphasizes the lack of prognostic significance of left ventricular function indexes and severity of coronary stenoses in surgically treated patients with CAD. These results continue the trend toward improved surgical survival shown in recent years.

Age Factors↗