Robert F. Wilson

The effect of coronary angioplasty on coronary flow reserve.

To determine the effects of coronary angioplasty on coronary flow reserve (CFR), we studied 32 patients before and immediately after single-vessel coronary angioplasty and 31 patients evaluated late after angioplasty (7.5 +/- 1.2 months, mean +/- SEM). The geometry (percent area stenosis and minimal cross-sectional area) of each lesion was determined by quantitative coronary angiography (Brown/Dodge method) and the integrated optical density was measured by videodensitometry. CFR was measured with a No. 3F coronary Doppler catheter placed immediately proximal to the lesion and a maximally vasodilating dose of intracoronary papaverine. The translesional pressure gradient was obtained in all lesions before and immediately after angioplasty and in 18 of 31 vessels late after angioplasty. CFR immediately after angioplasty returned to normal levels (greater than 3.5 peak/resting velocity ratio) in 14 of 31 patients and was improved, although not normalized, in the remaining 17 patients. CFR immediately after dilation was not significantly correlated with any of the angiographic variables of arterial stenosis nor the resting pressure gradient. Moreover, the pressure gradient and absolute distal coronary pressure at peak hyperemia were not significantly different in vessels with normal and those with abnormal flow reserve immediately after dilation, suggesting that the residual stenosis did not significantly limit hyperemia. Late after angioplasty, however, a significant relationship emerged between CFR and all four indexes of residual arterial stenosis (percent area stenosis r = .70, p less than .01; minimum arterial cross-sectional area r = .70, p less than .01; integrated optical density r = .60, p less than .01; and translesional pressure gradient r = .77, p less than .01). Furthermore, in the absence of restenosis, CFR eventually normalized in all patients. These findings demonstrate that in one-half of patients there is a transient reduction in coronary flow reserve immediately after angioplasty. In the absence of restenosis, coronary flow reserve later normalizes. Consequently, measurements of coronary flow reserve immediately after angioplasty may not reflect the eventual success of the procedure in removing physiologic obstruction to coronary blood flow.

Prediction of the physiologic significance of coronary arterial lesions by quantitative lesion geometry in patients with limited coronary artery disease.

Studies in animals with normal coronary arteries have shown that coronary flow reserve can be predicted by angiographic measurements of arterial stenosis. Studies in man, however, suggest that even quantitative analysis of coronary angiograms cannot predict the physiologic significance of individual coronary lesions. These studies, however, were carried out in patients with either widespread, diffuse coronary artery disease or by measurement techniques that tend to underestimate maximal coronary flow reserve. To determine the relationship between coronary arterial stenosis and coronary flow reserve (CFR) in patients with discrete limited coronary atherosclerosis, we studied 50 patients with a single discrete coronary stenosis in only one or two vessels. The minimum coronary arterial cross-sectional area (mCSA), percent area stenosis (%AS), and percent diameter stenosis in the left and right anterior oblique projections were determined by the Brown/Dodge method of quantitative coronary angiography. A No. 3F coronary Doppler catheter was placed immediately proximal to the lesion. Measurements of CFR were obtained by intracoronary administration of papaverine in doses sufficient to provide maximal arteriolar vasodilation. In 25 patients, a translesional pressure gradient was obtained with an angioplasty catheter. CFR measured in patients with coronary artery disease was compared with that in 13 patients with normal coronary vessels. In normal patients, CFR averaged 5.0 +/- 0.6 (peak/resting velocity ratio; mean +/- SEM, range 3.7 to 8.2). In patients with limited coronary artery disease, CFR was closely correlated with %AS (r = .85), mCSA (r = .79), and the translesional pressure gradient (r = .83). Additionally, the most severe percent diameter stenosis in either the left or right anterior oblique view was also highly correlated with CFR (r = .82). Importantly, all arteries with lesions producing less than 70% area stenosis and less than 50% diameter stenosis, or with greater than 2.5 mm2 mCSA had CFR of over 3.5. These results suggest that, in contrast to the poor correlation of percent area and percent diameter stenosis to CFR measured in patients with multivessel coronary artery disease, CFR measured at angiography in patients with discrete, limited coronary artery disease correlates closely with luminal stenosis determined precisely with quantitative coronary angiography. Differences in the extent of diffuse arterial narrowing may account for these discrepancies.

Methods of measurement of myocardial blood flow in patients: a critical review.

During the past decade, major progress has been made in the evolution of technology directed toward the accurate measurement of regional myocardial perfusion in patients. The deficiencies of some of the older methods (thermodilution and gas clearance) are better appreciated and improved approaches (Doppler catheters, positron-emission tomography, and digital subtraction angiography) have been developed. The new approaches should play a major role in research and for most applications the older methods will gradually be replaced. Efforts to bring these new methods to community hospitals and practicing cardiologists should be stimulated. Doppler catheters, positron-emission tomography, and digital-subtraction angiography are commercially available and Doppler catheters and digital-subtraction angiography could be easily incorporated into routine cardiac catheterization procedures. The Doppler catheter is the most inexpensive and probably the simplest to apply. In our opinion, routine measurements of coronary flow reserve will significantly improve the care of patients with coronary obstructive disease and other diseases that impair myocardial perfusion. If coronary reserve measurements are used frequently, patient selection for coronary angioplasty and bypass surgery will no longer depend entirely on visual assessment of percent diameter stenosis, a very poor criterion in many situations. Also, patients with chest pain syndromes, normal coronary vessels, and impaired coronary reserve will be identified and perhaps some effective treatment for this condition will be devised.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation between echocardiographically demonstrated segmental dyskinesis and regional myocardial perfusion.

In order to evaluate the relationship between regional myocardial perfusion and segmental dyskinesis, 22 open chest dogs were studied using ultrasound to register cardiac wall motion and radioactive labeled microspheres to determine myocardial perfusion. In six dogs, motion and perfusion were correlated at two levels of partial circumflex coronary artery occlusion followed by complete occlusion. A good correlation between declining myocardial perfusion of all the ischemic segments and development of aneurysmal bulging (during isometric contraction) was seen: r = -0.80. A similar correlation between myocardial perfusion and endocardial wall velocity (during systolic ejection) was observed: r = 0.92. In nine dogs, the effect of 45 minutes of complete coronary occlusion followed by 30 minutes of reperfusion was evaluated with respect to perfusion and motion. After coronary reperfusion myocardial perfusion of the ischemic area returned to control levels (from 32.6 ± 3.5 to 130.3 ± 13.3 ml/100 g/min), but aneurysmal bulging during isometric contraction persisted. Endocardial wall velocity during systolic ejection showed a variable response to reperfusion, achieving values ranging from 32% to 162% of the preocclusion levels. In seven dogs the ultrasound beam was reflected off nonischemic myocardium adjacent to areas of ischemia resulting from coronary occlusion. Despite preservation of normal myocardial perfusion in these nonischemic areas wall motion abnormalities were evident: endocardial wall velocity declined from 25.8 ± 5.8 to 14.0 ± 4.9 mm/sec (P < 0.01), and aneurysmal bulging developed in three animals. These changes may be due to transient undetected ischemia in the segments struck by the ultrasound beam, or to passive alteration of the motion of the normally perfused areas by the severe dyskinesis of the adjacent ischemic myocardium.

Assessing the Physiologic Significance of Coronary Obstructions in Patients: Importance of Diffuse Undetected Atherosclerosis

T HE HALLMARK OF coronary atherosclerosis is an apparently localized obstruction of a conduit coronary vessel. Until Sones introduced the technique of selective coronary angiography,’ for the most part the anatomy of these localized coronary obstructions could only be defined at postmortem. The ability to anatomically define coronary obstructions with a broadly applicable clinical technique has vastly altered our approach to the diagnosis and treatment of coronary atherosclerosis. Each new step forward, however, immediately brings forth new questions. Thus, coronary angiography has forced physicians to develop approaches of defining the physiologic significance of coronary lesions that can be demonstrated angiographically. Accurately assessing the physiologic significance of coronary obstructive lesions is critical to clinical decision making. The need for coronary bypass surgery, percutaneous transluminal coronary angioplasty, the adequacy of prior bypass surgery and percutaneous transluminal coronary angioplasty, and the validation of noninvasive approaches to the diagnosis of coronary disease all critically depend on assessing the physiological significance of coronary obstructive lesions. For more than two decades, the physiological significance of coronary obstructions detected by coronary angiography has been assessed primarily by visual estimates of percent stenosis. To a lesser extent clinicians have used other aspects of the patients’ clinical presentation including symptoms and results of various noninvasive procedures. Because percent stenosis remains the gold standard today in more than 99% of hospitals that perform coronary angiography, this review will examine the advantages and disadvantages of this approach.

Sensitivity and specificity of assessing coronary bypass graft patency with ultrafast computed tomography: results of a multicenter study.

Because a significant number of all patients seen by cardiologists have had coronary bypass surgery, a relatively noninvasive method of assessing coronary bypass graft patency would be very helpful. Ultrafast computed tomography, by virtue of its rapid data acquisition time and reasonable spatial resolution, may be useful in this regard. To determine the sensitivity, specificity and predictive accuracy of this imaging modality as compared with cardiac catheterization, a multicenter study was undertaken. There were two parts to the study. Part I involved the evaluation of 179 grafts in 74 patients studied in the five participating centers between March 1985 and August 1986. Twenty-nine percent of these graft studies were found to be technically inadequate and were excluded before patency determinations began. The remaining group of 127 bypass grafts in 62 patients had studies adequate for interpretation. Fifty-one grafts were to the left anterior descending coronary artery or a diagonal branch, 37 to branches of the left circumflex artery and 28 to the right coronary artery or a posterior descending vessel; in addition, there were 11 internal mammary artery bypass grafts primarily into the left anterior descending or diagonal artery distribution. The sensitivity of detecting angiographically open grafts was 93.4%, the specificity of detecting angiographically closed grafts 88.9% and the predictive accuracy was 92.1%. A subsequent study (Part 2) was performed 9 months later to assess the ability to carry out technically adequate examinations. Of the 138 consecutive graft examinations (50 patients) included in this part of the study, 94.2% of the examinations were found to be technically adequate.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of acute coronary occlusion on the motion and perfusion of the normal and ischemic interventricular septum.

SUMMARY To establish the effect of local and remote myocardial ischemia on interventricular septal motion, 27 open-chest dogs were studied using ultrasound and radioactive microspheres. In 14 dogs the left anterior descending coronary artery was ligated. If the ultrasound beam traversed ischemic septum (proximal LAD occlusion), significant (P < 0.05) declines in systolic septal velocity (26.4 ± 2.9 to 6.4 ± 1.8 mm/sec), and excursion (2.6 ± 0.3 to 0.7 ± 0.2 mm) occurred, and systolic thickening was reduced. Similar significant changes were seen when the ultrasound beam traversed non-ischemic septum adjacent to the ischemic area (distal LAD occlusion). In 13 additional dogs, circumflex coronary ligation produced posterior ischemia. The mean septal velocity for this group increased significantly (21.8 ± 2.6 to 26.5 ± 3.3 mm/sec), as did the septal excursion (2.5 ± 0.2 to 3.1 ± 0.4 mm). We conclude that acute LAD occlusion causes a reduction in systolic velocity, excursion, and thickening of both the involved ischemic and the adjacent nonischemic septum. When myocardial ischemia was produced in a part of the ventricle remote from the septum, septal velocity and excursion increased.

Automated analysis of coronary arterial morphology in cineangiograms: geometric and physiologic validation in humans

A method of coronary border identification is discussed that is based on graph searching principles and is applicable to the broad spectrum of angiographic image quality observed clinically. Cine frames from clinical coronary angiograms were optically magnified, digitized, and graded for image quality. Minimal lumen diameters, referenced to catheter size, were derived from automatically identified coronary borders and compared to those defined using quantitative coronary arteriography and to observer-traced borders. computer-derived minimal lumen diameters were also compared to intracoronary measurements of coronary vasodilator reserve, a measure of the functional significance of a coronary obstruction. To test the robustness of the present border detection method, computer-derived coronary borders were compared to independent standards separately for good and poor angiographic images. The accuracy of computer-identified borders was similar in the two cases.

Videodensitometric analysis of coronary stenoses in vivo geometric and physiologic validation in humans

Assessment of the severity of coronary stenoses on arteriograms conventionally is based on subjective estimates of percent luminal diameter narrowing. However, in studies in patients with multivessel coronary artery disease, we have found a poor correlation between percent stenosis and the physiologic significance of an individual coronary obstruction. The purpose of this study was to determine whether computerized videodensitometry would allow estimation of coronary luminal area and therefore prediction of the physiologic significance of individual coronary stenoses in humans. Videodensitometry was used to define the minimal luminal area of 15 left anterior descending, 15 circumflex, and 15 right coronary artery segments in 43 patients. Computer-assisted quantitative coronary arteriography (method of Brown et al) was used to determine the minimal luminal cross-sectional area of these same segments. In each arterial segment, coronary vasodilator reserve was assessed using intraoperative (n = 18 segments) or intracoronary (n = 27 segments) Doppler measurements of coronary vasodilator reserve. Videodensitometric estimates of coronary luminal area correlated well with minimal luminal area defined using the independent geometric technique of quantitative coronary arteriography (r = 0.82, y = 0.97 X + 0.71, SEE = 1.83 mm2, n = 45) and with lesion physiologic significance as defined by studies of the peak-to-resting velocity ratio (r = 0.71, 0.92, and 0.74 for the left anterior descending, circumflex, and right coronary arteries, respectively). Thus, videodensitometry is a promising method that may supplement geometric approaches to quantitative analysis of coronary arteriograms in humans.

Post Thrombolytic Care

The administration of streptokinase following acute myocardial infarction effectively lyses occlusive thrombi superimposed on atherosclerotic lesions and thereby allows for reperfusion of a previously occluded vessel. When given early in the course of myocardial infarction either intravenous or intracoronary streptokinase may have a favorable effect on both subsequent mortality and the extent of myocardial dysfunction. However, the clinical course following the administration of streptokinase for myocardial infarction is not only influenced by the presence and extent of myocardial necrosis but also by factors related to thrombolytic therapy. Thus the patient who has received thrombolytic therapy after myocardial infarction is exposed to several additional risks. In this review we will discuss these additional factors that influence the clinical course of these patients. Much of the data that we will present has been derived from patients who have received intracoronary streptokinase, yet are relevant to patients who have received intravenous streptokinase.