Coronary arterial remodeling studied by high-frequency epicardial echocardiography: an early compensatory mechanism in patients with obstructive coronary atherosclerosis.

Coronary arterial remodeling is a compensatory mechanism that may limit the adverse effects of coronary obstructive lesions by expansion of the entire vascular segment. To determine if this compensatory anatomic change occurs in patients, high-frequency epicardial echocardiography using a 12 MHz transducer was performed during open heart surgery in 33 patients (10 with normal coronary arteries undergoing valvular surgery and 23 with coronary atherosclerosis). From stop-frame videotape high-frequency epicardial echocardiographic images, cross-sectional measurements of luminal area and total arterial area (lumen, intima, media and dense adventitia) were made in the patients with atherosclerosis at the site of arterial lesions and from the most proximal portion of the same artery. Remodeling was defined as enlargement of the total arterial area. In normal arteries measurements were made from proximal and midarterial locations. In the patients with normal coronary arteries, total arterial area, as determined by high-frequency echocardiography, decreased from the proximal site to the midportion of the artery (from 10.4 +/- 0.9 to 8.4 +/- 1.0 mm2, p less than 0.05); luminal area also decreased (from 6.0 +/- 0.6 to 4.5 +/- 0.7 mm2, p less than 0.05). In patients with coronary arterial lesions, luminal area also decreased from the proximal site to the arterial lesion site (from 5.3 +/- 0.6 to 2.3 +/- 0.3 mm2, p less than 0.05), but total arterial area increased (from 11.6 +/- 1.0 to 13.0 +/- 1.0 mm2, p less than 0.05). Of the 25 coronary arteries evaluated, only 4 had angiographic evidence of coronary collateral formation. These data indicate that coronary arterial remodeling is an important compensatory mechanism in obstructive coronary disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Outlet strut fracture of the Björk-Shiley 60 degrees Convexo-Concave valve: current information and recommendations for patient care.

Mechanical failure of artificial heart valves can be a catastrophic event. The problem of outlet strut fracture of the Björk-Shiley 60 degrees Convexo-Concave tilting disc prosthesis has received much attention in the medical literature and generated both concern and confusion among patients and physicians. Analysis of current data from the manufacturer, as well as a review of the medical literature, suggests that the overall risk of outlet strut fracture is low and that elective explantation of a well functioning Björk-Shiley 60 degrees Convexo-Concave valve prosthesis is not warranted. Diagnostic features of outlet strut fracture can be seen with overpenetrated chest X-ray films so that diagnosis can be established promptly. Early operation to replace the fractured prosthesis is essential for patient survival.

Management of radiation-induced accelerated carotid atherosclerosis.

Patients with long survival following cervical irradiation are at risk for accelerated carotid atherosclerosis. The neurologic presentation in these patients mimics naturally occurring atheromatous disease, but patients often present at younger ages and with less concurrent coronary or systemic vascular disease. Hypercholesterolemia also contributes to this accelerated arteriosclerosis. Angiographic findings in this disorder include disproportionate involvement of the distal common carotid artery and unusually long carotid lesions. Pathologic findings include destruction of the internal elastic lamina and replacement of the normal intima and media with fibrous tissue. This article describes two surgical patients with radiation-induced accelerated carotid atherosclerosis who typify the presentation and characteristics of this disease.

Abnormalities in the coronary circulation that occur as a consequence of cardiac hypertrophy.

Myocardial ischemia is frequently observed in patients with cardiac hypertrophy even when the conduit coronary arteries are normal. Recent studies indicate that impaired coronary reserve in hypertrophied hearts probably occurs because growth of the coronary bed does not keep pace with increases in cardiac mass. The imbalance between vascular proliferation and muscle growth is probably most severe when cardiac hypertrophy is produced by pressure overload. Experimental studies also suggest that abnormalities intrinsic to pressure-hypertrophied heart muscle (decreased capillary density; decreased coronary reserve; electrophysiologic abnormalities) adversely affect the response of the enlarged heart to sudden coronary occlusion. When animals with hypertension and left ventricular hypertrophy are subjected to sudden coronary occlusion, the incidence of sudden cardiac death is increased severalfold and infarct size is substantially augmented. These observations suggest that abnormalities in the coronary microcirculation that accompany cardiac hypertrophy play a significant role in the pathogenesis of the complications associated with cardiac hypertrophy.

Coronary reserve in volume-induced right ventricular hypertrophy from atrial septal defect.

To assess coronary reserve in patients with right ventricular (RV) hypertrophy secondary to volume overload, the quantitative characteristics of coronary reactive hyperemia were examined in 20 patients with a large atrial septal defect (ASD). The control group consisted of 13 patients who had undergone elective cardiac surgery for abnormalities that did not involve the right ventricle or its blood supply. Coronary blood flow velocity was measured in RV branches of the right coronary artery at cardiac surgery. Echocardiographic measurements of RV diameter in ASD and in control patients (2.3 +/- 0.2 and 1.1 +/- 0.2 cm, respectively, p less than 0.05) documented the presence of substantial RV enlargement in patients with ASD. In patients with ASD and in control subjects, a 20-second coronary occlusion produced maximal coronary dilation. After release of a 20 second coronary occlusion, the peak-to-resting velocity ratio in ASD and in control patients was 3.1 +/- 0.2 and 5.5 +/- 0.1, respectively (p less than 0.05). The 50% decrease in the ratio of peak-to-resting coronary blood flow velocity, a measure of relative coronary reserve, in patients with ASD suggests that coronary reserve is compromised in volume-induced RV hypertrophy. These studies support the concept that in humans, volume-induced RV hypertrophy substantially decreases coronary reserve.

Can atherosclerotic coronary arteries vasodilate? An intraoperative high-frequency epicardial echocardiographic study.

Our purpose was to evaluate the vasodilating responses of atherosclerotic coronary arteries using intraoperative high-frequency (12 MHz) epicardial echocardiography. We obtained continuous high-frequency epicardial echocardiographic recordings during surgery, and determined cross-sectional lumen area from 17 coronary arterial segments (12 patients). Nitroglycerin (100 to 400 micrograms/min) was administered intravenously to reduce mean (+/- SEM) arterial pressure 14 +/- 1.8 mm Hg. The cross-sectional arterial images were classified using 3 different parameters: arterial lumen area, percentage of the arterial wall circumference that was atherosclerotic (wall thickness > 0.7 mm), and presence of an eccentrically shaped arterial lumen (maximal/minimal luminal diameter > 1.5). Nine arterial segments had small (< 5.0 mm2) arterial lumens (1.7 +/- 0.40 mm2 [+/- SEM; range 0.6 to 3.9]). With nitroglycerin, the luminal area increased 0.8 +/- 0.28 mm2 (range 0 to 2.5), and 39 +/- 12.1% (range 0 to 117). The remaining 8 segments had larger (> 5.0 mm2) lumens (8.7 +/- 0.91 mm2 [range 5.0 to 11.9]). With nitroglycerin the luminal area increased 4.3 +/- 1.11 mm2 (range 1.4 to 11.4), and 51 +/- 10.2% (range 16 to 96). Seven arterial segments had eccentric lumens; mean maximal/minimal ratio was 1.8 +/- 0.08 (range 1.6 to 2.0). The area increased 39 +/- 7.3% (range 16 to 71) with nitroglycerin. In the 10 concentrically shaped lumens (maximal/minimal lumen diameters 1.3 +/- 0.04 [range 1.1 to 1.5]), nitroglycerin increased luminal area by 48 +/- 12.6% (range 0 to 117) (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Spiral vein graft: an alternative method for relief of superior vena caval obstruction following the Mustard repair.

This report describes our experience with an 11-year-old girl with superior vena caval syndrome following an intra-atrial baffle for transposition of the great arteries. She underwent a saphenous spiral vein graft with excellent relief of the obstruction. This method is presented as an alternative to the use of cardiopulmonary bypass for baffle revision and direct anastomosis of the innominate vein to the left atrial appendage when the latter is not feasible.

Thrombosis of the Björk-Shiley prosthesis: illustrative cases and review of the literature.

Thrombosis of the Björk-Shiley prosthetic cardiac valve may occur in any valve position and regardless of anticoagulant status. Four illustrative cases are presented to demonstrate management problems. Review of cases reported in the literature suggests the minimal incidence of thrombosis of Björk-Shiley prostheses is about 2% in the aortic position and about 4% in the mitral position. Prevention of this complication appears to require continuous systemic anticoagulation with warfarin; even temporary interruption or alteration of anticoagulant regimen may be detrimental. Although changes in anticoagulation may rarely precipitate sudden thrombosis, in most cases a period averaging 10 months is required for pannus of organized thrombus to build up enough to cause acute thrombosis and malfunction of the valve. Operation to remove thrombus or replace the prosthesis is usually required for left-sided cardiac prostheses, but thrombosed valves in the tricuspid position may be successfully treated with fibrinolytic medical therapy.

Effect of valve orientation on flow development past aortic valve prostheses in a model human aorta.

The effect of valve orientation on flow development in a model human aorta was studied by means of a qualitative flow visualization technique. The model replicated the geometry of the human aorta and the experiment simulated a physiologically realistic pulsatile flow. The following valves were studied: Starr-Edwards Stellite, Starr-Edwards silicone, Björk-Shiley spherical disc, Björk-Shiley convexo-concave disc, and Hall-Kaster tilting disc. All the valves had a tissue anulus diameter of 27 mm. With the ball-in-cage valves, the flow in the ascending aorta was predominantly axial and uniform throughout systole, while vortex formation was observed downstream from the ball. With the tilting disc valves, the flow development in the aorta was a function of the orientation of the valves. With the major flow orifice directed toward the commissure between the right and noncoronary cusps, the fluid motion was predominantly in the axial direction through early systole. A vortex developed along the wall of lesser curvature of the aorta with the progression of systole. In early diastole, a well-defined flow reversal was observed along the lesser curvature of the aorta. With the major flow orifice directed toward the left coronary cusp, the fluid motion, although predominantly axial, was not uniform in the ascending aorta. Regions of relative stasis present near the wall of greater curvature subsequently developed into a trapped vortex throughout the cardiac cycle. With the major flow orifice directed more posteriorly, an improved fluid dynamic characteristic was observed, and there was no trapped vortex present near the wall of greater curvature. The flow visualization study in the model human aorta suggests that, from a fluid dynamic point of view, orientation of the major flow orifice of the tilting disc valve toward the wall of lesser curvature is not advisable.

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.

In vivo comparison of replamineform, Silastic, and bioelectric polyurethane arterial grafts.

The replamineform process allows fabrication of microporous prostheses with control of both pore diameter and structural geometry by means of a variety for biomaterials. Tubular prostheses 3 cm long, 6 mm inside diameter, and 1 mm wall thickness were made of Silastic or Bioelectric Polyurethane (BEP) with use of a template of the echinoderm Heterocentrotus mammillatus. Pore diameter of the prosthesis wall was 18 to 25 mu. Light and scanning-electron microscopy of grafts removed between 1 and 32 weeks demonstrated that organization and endothelialization of neointima were similar for both polymers, being complete by 4 to 8 weeks. However, the character of prosthesis wall ingrowth was strikingly different: the microporous lattice of BEP was completely ingrown early, but was apparently fragmented by continued granulomatous inflammation by 32 weeks, while Silastic generated minimal inflammatory response and slower fibrous tissue and capillary ingrowth. Thus, with Silastic and BEP, similarities in neointima organization appeared independent of distinct differences in wall ingrowth. The replamineform process is a unique means of studying surface healing and wall ingrowth of different biomaterials as microporous vascular prostheses in a controlled fashion.

Thoracoscopic internal mammary artery harvest for MICABG using the Harmonic Scalpel.

BACKGROUND: Thoracoscopic internal mammary artery (IMA) harvest is technically demanding, particularly on the left side. We have devised a Harmonic Scalpel (Ethicon Endo-Surgery, Cincinnati, OH) technique to facilitate this procedure, and describe our clinical experience here. METHODS: The Harmonic Scalpel functions with ultrasonic energy, producing less smoke and lower heat than regular electrocautery. A total of 27 (22 left and 5 right) pedicles of the IMA in 23 patients were harvested from the upper margin of the first rib or higher to the lower margin of the fifth rib thoracoscopically using the Harmonic Scalpel with a hook blade. RESULTS: In each case, the IMA harvest was completed thoracoscopically with only the Harmonic Scalpel, decreasing instrument transfers. Each vascular branch was coagulated without charring and was transected with excellent hemostasis. Smokeless views were provided. In the first 17 harvests, Doppler studies 3 months after the procedures demonstrated patent IMAs to the coronary circulation. CONCLUSIONS: The Harmonic Scalpel facilitates thoracoscopic IMA harvest and is expected to minimize hyperthermic damage of the IMA.

Bilateral simultaneous lung lavage utilizing membrane oxygenator for pulmonary alveolar proteinosis in an 8-month-old infant.

Pulmonary alveolar proteinosis can result in severe hypoxemia. Treatment of symptomatic patients using unilateral or lobar staged lung lavage often results in improved oxygenation and functional capacity. Lung lavage is technically difficult in infants and small children because of inability to ventilate part of the lung safely and adequately during lavage of other areas. We used extracorporeal membrane oxygenation to facilitate adequate gas exchange during lung lavage for severe respiratory failure in a 3.7 kg, 8-month-old child with pulmonary alveolar proteinosis. Oxygenation was markedly improved immediately following the procedure. Extracorporeal membrane oxygenation permits satisfactory respiratory support in the setting of severe respiratory failure and should be considered an adjunct for treatment of pulmonary alveolar proteinosis when lung lavage cannot be otherwise safely accomplished.

Aortic insufficiency requiring valve replacement in Whipple's disease.

Reviews of postmortem reports on patients with Whipple's disease (intestinal lipodystrophy) describe gross valvular deformity in more than 50% with characteristic histological findings of macrophages containing periodic acid-Schiff-positive, diastase-resistant granules. Frequently, congestive heart failure characterizes the terminal stages. In a 58-year-old man with well-documented Whipple's disease for 5 years, gastrointestinal, joint, and pericardial involvement apparently resolved with medical therapy. However, 10 years later, severe aortic insufficiency necessitated prosthetic valve replacement, at which time gross and histological examination of the excised valve demonstrated characteristic changes of Whipple's disease. Clinical recognition of the importance of cardiac valvular abnormalities and of possible late cardiac decompensation mandates close observation of patients with Whipple's disease. Corrective operation should improve the patient's chances of survival.

Intraoperative high-frequency epicardial echocardiography in coronary revascularization: locating deeply embedded coronary arteries.

During coronary revascularization, the precise location of major coronary arteries may be obscured by overlying fat, myocardial bridging, or epicardial scarring. High-frequency epicardial echocardiography can be used intraoperatively to quickly image and locate such arteries and eliminate the need for time-consuming epicardial exploration or potentially deleterious retrograde probing of distal coronary artery branches. This technique can be applied using commercially available equipment and the aid of a skilled technician.

Coronary obstructive lesions: assessing their physiological significance in humans.

For more than two decades cardiologists and cardiac surgeons have estimated the physiologic significance of coronary lesions by measuring percent stenosis of the obstructive vascular segment from coronary angiograms. Such measurements, when performed without computer-based analysis, are associated with substantial variability between observers, as well as within a single observer. In addition, recent intraoperative measurements of coronary reserve in individual obstructed vessels of patients with multivessel coronary disease performed with a suction Doppler probe indicate that, in the intermediate range (10% to 90% diameter stenosis), percent stenosis measurements of coronary lesions by angiography correlates poorly with coronary reserve. These studies suggest that the physiologic significance of coronary obstructions cannot be accurately assessed by visual interpretation of coronary angiograms. More sophisticated and accurate approaches are needed for assessing the physiologic significance of coronary obstructions preoperatively.

The effects of cardiopulmonary bypass and cold cardioplegia on coronary flow velocity and the reactive hyperemic response in patients and dogs.

In normal coronary arteries, reactive hyperemic responses to a 20-second occlusion, an index of coronary reserve, usually demonstrate a peak-to-resting flow velocity ratio of 4:1 or more. Most intraoperative studies that have assessed reactive hyperemic responses in bypassed vessels have reported peak-to-resting flow velocity ratios of 2:1 or less following a 20-second occlusion. These decreased reactive hyperemic responses could be due to coronary vasodilatation after cardiopulmonary bypass or to an inadequate physiological result of the surgical procedure. In 14 patients with angiographically normal coronary arteries, the peak-to-resting flow velocity ratio following a 20-second coronary occlusion decreased significantly (p less than 0.05) from 4.4 +/- 0.2 (mean +/- standard error) before bypass to 3.0 +/- 0.3 after bypass. In a similar dog model, the peak-to-resting flow velocity ratio decreased by 36 to 52% during the first hour following one hour of cardiopulmonary bypass and cardioplegia. During the same period, left ventricular perfusion increased 21 to 30%, mean arterial pressure and coronary vascular resistance decreased, and myocardial oxygen consumption was unchanged. In a second group of dogs studied for the effects of duration (200 to 240 minutes) of anesthesia and thoracotomy alone, peak-to-resting flow velocity ratio was significantly lower. These clinical and experimental studies suggest that major coronary vasodilatation occurs early following cardiopulmonary bypass and cold cardioplegia, and may contribute to the blunted coronary reactive hyperemic responses reported during this time. Consequently, an intraoperative peak-to-resting flow velocity ratio of 3:1 for bypassed coronary arteries may represent an excellent physiological result.

Sternotomy infection: poor prediction by acute phase response and delayed hypersensitivity.

Two hundred twenty-one consecutive adult cardiac surgical patients were examined prospectively for nutritional protein state, acute phase protein response, and delayed hypersensitivity reaction in an attempt to identify patients at high risk for the development of sternal wound infection, which occurred in 6 patients (2.7%). There was no significant correlation between preoperative nutritional protein concentrations (retinol-binding protein, prealbumin, and transferrin) and acute phase protein levels (C-reactive protein, alpha 1-acid glycoprotein, and complements B and C3), nor a statistically significant relationship between nutritional state or acute phase protein response and the development of sternal infection. Preoperative complement C3 levels were elevated, however, in 80.0% of those in whom sternal infections developed compared with 30.6% of those with well-healed wounds. Similarly, postoperative concentrations of alpha 1-acid glycoprotein were elevated in 80.0% of those in whom sternal infections developed compared with 28.6% of those with well-healed wounds. There was no correlation between delayed hypersensitivity and the risk of sternal infection, nor between preoperative nutritional protein and acute phase protein values. Seventy-three percent of patients were anergic on postoperative day 2. Stepwise logistic regression showed that age, body weight, preoperative intensive care unit stay, repeat median sternotomy, internal mammary artery grafting, postoperative hemorrhage, and postoperative cardiac arrest correlated with the development of sternal infection, whereas transfusion requirement, reexploration for bleeding, and the operation performed did not. We conclude that routine delayed hypersensitivity testing is of no value in predicting high-risk cardiac surgical patients when the anergy battery is placed on the preoperative day. Although statistically insignificant, possibly due to the small number of patients in whom sternal infection developed in this study (type II error), a larger study might find preoperative complement C3 and post-operative alpha 1-acid glycoprotein levels to be predictive of patients at risk for the development of sternal wound infection. The final logistic model for the predicted risk 2%) of sternal wound infection is: PREDSWC = exp(EQ)/1 + exp(EQ) where EQ = (0.38 x age) + (0.24 x weight) + (5.42 x preop ICU) + (4.39 x redo) + (7.14 x IMA) + (4.49 x hemorrhage) + (8.81 x arrest) - 62.72, and where preop ICU, redo, hemorrhage, and arrest are defined as yes (1) or no (0), IMA-is defined as 0, 1, or 2, age is in years, and weight is in kilograms.

Technical note: in vitro evaluation of an in-line Doppler flow-metering system for carotid artery shunts.

Carotid artery shunts are used extensively during carotid artery surgery to maintain cerebral perfusion. Blood flow through such shunts may be compromised by thrombosis, incorrect placement, or inadvertent clamping of the shunt. Currently, however, no direct method exists to detect poor shunt flow that might precipitate cerebral ischemia. A carotid artery shunt system that continuously monitors blood flow rates has been developed. This system utilizes a Doppler crystal embedded in the wall of a silicone elastomer shunt. The crystal ranges through a "liquid lens" that enables it to be placed without violation of the shunt lumen. Because the crystal is at a fixed angle (45 degrees) to the axis of blood flow and the diameter of the lumen remains constant, a linear relationship should exist between flow rates and the Doppler velocity signal. This hypothesis was tested in vitro using a pulsatile pump and both a starch-water solution and whole blood. Doppler velocity meter readings were compared to timed volume collections over a wide range of flow rates. A direct linear relationship between the Doppler flowmeter and timed volume collections existed, and the system was accurate to within 4.7%. This device may be useful in laboratory studies of carotid shunt dynamics and in clinical practice for early detection of correctable shunt flow abnormalities that could lead to cerebral injury.

Effect of wedging on the flow characteristics past tilting disc aortic valve prosthesis.

To evaluate the efficacy of implanting a tilting disc aortic valve prosthesis in an angulated (wedged) supra-annular position, an in vitro experimental study was performed. The aortic valve prosthesis was mounted in an axi-symmetric valve chamber in a wedged position and incorporated in a mock circulatory system. Measurements were obtained on the transvalvular pressure gradient, percent regurgitation as well as velocity profiles and turbulent normal stresses distal to the valve. Our results showed that there was no significant reduction in the pressure gradient in mounting a larger sized valve in the wedged supra-annular position. On the other hand, the percent regurgitation increased with increase in heart rate and wedge angle. The valve failed to function properly above 110 beats min-1 at any wedge angle with the normal flow rate. The velocity profiles also showed significant changes with an increase in the turbulent normal stress with increase in wedge angle. Hence our study suggests that implanting the tilting disc prosthesis in a wedged supra-annular position in the aorta is not advisable.