Enhanced intracoronary thrombolysis with urokinase using a novel, local drug delivery system. In vitro, in vivo, and clinical studies

BACKGROUND

Current pharmacological regimens for treating intracoronary thrombus in the cardiac catheterization laboratory generally involve the administration of thrombolytic agents that result in a systemic fibrinolytic state and/or require prolonged arterial drug infusion. The purpose of the present study was to assess a new technique for treating intracoronary thrombus consisting of the local infusion of limited quantities of urokinase with a novel drug delivery device.

METHODS AND RESULTS

THe Dispatch coronary infusion catheter is a new local drug delivery system that allows for the prolonged infusion of therapeutic agents at an angioplasty site while distal coronary flow is maintained. Three experimental protocols were performed to determine the in vitro, in vivo, and clinical efficacy of this device. First, in vitro thrombolysis of fresh, porcine thrombus trapped in a 4-mm plastic tube with a 50% constriction and perfused with 20% porcine plasma was measured. Twenty-three thrombi were weighed before and after no treatment (n = 5), "systemic" urokinase administration (n = 4), local infusion of 150,000 U urokinase with a standard end-hole catheter (n = 4), local infusion of saline with the Dispatch catheter (n = 5), and local infusion of 150,000 U urokinase with the Dispatch catheter (n = 5). Second, 25 porcine coronary arteries in 23 pigs were dilated in vivo with conventional balloon angioplasty and then treated with 123I-labeled urokinase that was administered either by the Dispatch catheter (150,000 U; n = 16), intravenous systemic bolus (1,000,000 U; n = 3), guiding catheter infusion (500,000 U; n = 3), or local end-hole catheter infusion (150,000 U; n = 3). All vessels were subsequently harvested to quantify intramural deposition and subsequent washout of urokinase at the angioplasty site. Finally, 19 patients with angiographic evidence of intracoronary thrombus were treated with local urokinase infusion with the Dispatch catheter either before or after balloon angioplasty or directional atherectomy. In vitro studies demonstrated that infusion of urokinase with the Dispatch catheter decreased thrombus weight by 66% compared with no treatment (-25%), "systemic" urokinase administration (25%), end-hole catheter urokinase infusion (32%), or infusion of saline by the Dispatch catheter (32%) (P < or = .005). In vivo studies demonstrated immediate deposition of 0.12% of the urokinase delivered by the Dispatch catheter to the angioplasty site, compared with 0.0007% with systemic bolus, 0.003% with guiding catheter infusion, and 0.007% with local infusion with an end-hole catheter (P < .001). Urokinase deposited by the Dispatch catheter persisted intramurally for at least 5 hours. Patient studies demonstrated reduction of thrombus-containing stenoses and complete disappearance of intracoronary thrombus in all cases in which 150,000 U urokinase was locally infused over 30 minutes. There was no evidence of abrupt closure, distal embolization, or no reflow in any patient.

CONCLUSIONS

Local urokinase delivery with the Dispatch catheter can result in rapid and complete intracoronary thrombolysis using substantially less drug than standard thrombolytic techniques. Intramural deposition of drug with this technique creates a local reservoir of urokinase that may provide prolonged thrombolytic activity at the infusion site.

Treatment of acute stent thrombosis with local urokinase therapy using catheter-based, drug delivery systems: a case report

Abrupt thrombotic stent closure remains a difficult problem to treat in the cardiac catheterization laboratory. A 63-yr-old white female initially underwent successful placement of a Palmaz-Schatz biliary stent in the proximal RCA following failed coronary angioplasty. One week later, the patient represented with an acute inferior infarction and thrombotic occlusion of the stent site in spite of adequate anticoagulation. A new, local drug infusion catheter (the Dispatch catheter) was placed at the angioplasty site and 150,000 units of urokinase were locally infused, with immediate restoration of normal distal flow and a subsequent marked decrease in angiographic thrombus. A small, residual thrombotic filling defect was further treated with a urokinase-coated hydrogel balloon (Hydro Plus). Following local urokinase delivery with the Dispatch catheter and hydrogel balloon, there was complete resolution of angiographic thrombus with TIMI 3 flow and no evidence of distal embolization or no-reflow. Local urokinase delivery directly to the site of thrombus with catheter-based drug delivery systems may be a useful technique for rapidly lysing intracoronary clot and re-establishing coronary flow in the setting of acute stent thrombosis.

Site-specific, catheter-based thrombolysis: a new technique for treating intracoronary thrombus and thrombus-containing stenosis

Site-specific thrombolysis is a new technique for treating intracoronary thrombus and thrombus-containing stenoses that is currently under active investigation and that involves the local delivery of thrombolytic agents directly to intraluminal clot using catheter-based technology. The theoretic mechanisms of thrombolysis underlying this approach involves the "trapping" of thrombus in an environment of high thrombolytic drug concentration, mechanical disruption of intraluminal clot by the drug delivery catheter itself, and intramural deposition of lytic agents with the creation of a drug reservoir that may provide for prolonged local thrombolysis. To date, preliminary studies have documented enhanced local thrombolysis with urokinase using two new drug delivery systems--the Dispatch catheter and the hydrogel-coated balloon. In 68 patients that have been reported to date, use of these two new systems has resulted in enhanced intracoronary thrombolysis using much less urokinase than involved in standard infusion protocols, and with low complication rates. These preliminary observations will be further studied in two multicenter randomized protocols comparing local drug delivery with standard techniques for treating intracoronary thrombus.

Treatment of intracoronary thrombus with local urokinase infusion using a new, site-specific drug delivery system: the Dispatch catheter

BACKGROUND

The presence of intracoronary thrombus significantly increases the risk of conventional balloon angioplasty because of a high incidence of abrupt closure, distal embolization, and no-reflow phenomenon. The purpose of this study was to assess a new technique for treating intracoronary thrombus consisting of the local delivery of urokinase directly to the angioplasty site with a novel, catheter-based, drug delivery system.

METHODS

The Dispatch catheter is a new local, drug-delivery device that allows for the prolonged infusion of therapeutic agents at an angioplasty site while still maintaining distal coronary perfusion. Six patients with angiographic or clinical evidence of intracoronary thrombus were treated with 150,000 units of urokinase over a 30-min period using this device prior to or following conventional balloon angioplasty and/or directional atherectomy.

RESULTS

Successful delivery of urokinase directly to the angioplasty site was achieved in all 6 patients without hemodynamic or electrocardiographic compromise. In all six cases, local urokinase therapy resulted in complete dissolution of angiographic intracoronary thrombus and/or reduction of the coronary stenosis. Limited ischemia due to side-branch occlusion by the catheter's coils was noted in one patient. Distal embolization or no-reflow phenomenon were not observed in any case.

CONCLUSION

The local drug-delivery catheter used in this study was able to successfully and rapidly achieve intracoronary thrombolysis by delivering limited quantities of urokinase directly to the angioplasty site, while still maintaining distal coronary perfusion. This technique of local, thrombolytic drug delivery may be useful in the percutaneous treatment of intracoronary thrombus and thrombus-containing stenoses.

Intracardiac ultrasound determination of left ventricular volumes: in vitro and in vivo validation

OBJECTIVES

This study was designed to assess the feasibility of calculating left ventricular volumes using intracardiac ultrasound.

BACKGROUND

Previous studies have validated transthoracic echocardiographic determinations of left ventricular volumes and have indicated the superiority of Simpson rule reconstruction algorithms. The feasibility of imaging the left ventricle with intracardiac ultrasound has also been demonstrated.

METHODS

The determination of left ventricular volumes with Simpson rule reconstruction of intracardiac ultrasound images was evaluated in two phases. In vitro validation was performed in 29 animal hearts preserved in either a nondistended or distended state. Latex cast volumes were the reference standard. In vivo studies used 14 pigs, and compared intracardiac ultrasound volumes and ejection fraction with single-plane contrast angiographic values. A 12.5-MHz device was used to record short-axis images at 0.5-cm intervals. These were used to reconstruct the ventricle as a stack of cylindric elements using all imaged levels as well as sections recorded every 1 and 2 cm and at a single midventricular level.

RESULTS

In the in vitro hearts, when all recorded sections were used, there was excellent agreement between intracardiac ultrasound and latex cast volumes (intracardiac ultrasound volume = 0.89 latex cast volume + 2.22, r = 0.95; intracardiac ultrasound volume = 0.97 latex cast volume + 0.91, r = 0.99) for nondistended and distended hearts, respectively. In vivo, there was again close correspondence between ultrasound and angiographic volumes (intracardiac ultrasound volume = 1.04 angiographic volume - 3.6, r = 0.91). The relation between intracardiac ultrasound and angiographic ejection fraction was fair (intracardiac ultrasound ejection fraction = 1.00 angiographic ejection fraction + 6.85, r = 0.69). Excellent correlations for the volumes were maintained as the number of cross sections was reduced to those recorded every 1 and 2 cm (r = 0.87 to 0.99). With a single midventricular site more variable but generally good correlations were obtained (r = 0.77 to 0.99).

CONCLUSIONS

The application of Simpson rule reconstruction to short-axis images of the left ventricle obtained with intracardiac ultrasound provides accurate determination of left ventricular volumes in animal hearts. This technique may prove useful in the analysis of left ventricular structure and function.

Effect of low-grade conductive heating on vascular compliance during in vitro balloon angioplasty

Radiofrequency-powered, thermal balloon angioplasty is a new technique that enhances luminal dilatation with less dissection than conventional angioplasty. The purpose of this study was to assess the effect of radiofrequency heating of balloon fluid on the pressure-volume mechanics of in vitro balloon angioplasty and to determine the histologic basis for thermal-induced compliance changes. In vitro, radiofrequency-powered, thermal balloon angioplasty was performed on 46 paired iliac segments freshly harvested from 23 nonatherosclerotic pigs. Balloon inflations at 60 degrees C were compared to room temperature inflations in paired arterial segments. Intraballoon pressure and volume were recorded during each inflation as volume infusion increased pressure over a 0 to 10 atm range. Pressure-volume compliance curves were plotted for all dilatations. Six segments were stained to assess the histologic abnormalities associated with thermal compliance changes. Radiofrequency heating acutely shifted the pressure-volume curves rightward in 20 of 23 iliac segments compared to nonheated controls. This increase in compliance persisted after heating and exceeded the maximum compliance shift caused by multiple nonheated inflations in a subset of arterial segments. Histologically, heated segments showed increased thinning and compression of the arterial wall, increased medial cell necrosis and altered elastic tissue fibers compared to nonheated specimens. In conclusion, radiofrequency heating of intraballoon fluid to 60 degrees C acutely increases vascular compliance during in vitro balloon angioplasty of nonatherosclerotic iliac arteries. The increased compliance persists after heating and can be greater than the compliance shifts induced by multiple conventional dilatations. Arterial wall thinning and irreversible alteration of elastic tissue fibers probably account for thermal compliance changes.

Decreased platelet deposition and smooth muscle cell proliferation after intramural heparin delivery with hydrogel-coated balloons

BACKGROUND

In vitro and in vivo studies have demonstrated both anticoagulant and antiproliferative effects of heparin. The purpose of this study was to assess the effect of local intramural delivery of heparin, using heparin-coated hydrogel balloons, on platelet deposition and early smooth muscle cell proliferation after in vivo balloon angioplasty.

METHODS AND RESULTS

The effects of local heparin delivery were assessed during balloon angioplasty of porcine peripheral arteries. All balloon dilatations were performed with oversized hydrogel balloons coated with a known quantity of heparin. Balloon dilatations in contralateral vessels with uncoated hydrogel balloons served as study controls. The pharmacokinetics of heparin delivery were assessed using 3H-heparin to quantitate heparin wash-off from the balloon surface, heparin delivery to the arterial wall, and intramural persistence of drug. Platelet deposition at 1 hour after balloon injury was quantified using 111In-labeled platelets. Smooth muscle cell proliferation was assessed 6 to 7 days after angioplasty with immunohistochemical staining for proliferating cell nuclear antigen. 3H-heparin wash-off from the hydrogel balloon surface occurred rapidly, with approximately 95% of the heparin coating disappearing within 10 seconds in the intact circulation. Approximately 2% of heparin on the balloon surface was delivered intramurally at the time of angioplasty. Intramural heparin dissipated rapidly, although small amounts of intramural heparin could still be detected for at least 48 hours. In comparison to control vessels, there was less 111In-platelet deposition (P = .002) and less medial smooth muscle cell proliferation (P = .03) in heparin-treated vessels.

CONCLUSIONS

Local intraluminal delivery of heparin at the time of balloon angioplasty with heparin-coated hydrogel balloons results in intramural deposition of drug that persists for at least 48 hours. This in vivo technique significantly decreases platelet deposition and early smooth muscle cell proliferation after angioplasty injury.

Localized intramural drug delivery during balloon angioplasty using hydrogel-coated balloons and pressure-augmented diffusion

OBJECTIVES

This study was designed to assess the feasibility of using hydrogel-coated balloons to deliver biologically active agents to the blood vessel wall.

BACKGROUND

The local intramural delivery of therapeutic agents during balloon angioplasty has been proposed as an adjunctive technique for preventing early intracoronary thrombosis and late restenosis.

METHODS

To assess the efficacy of delivery and depth of penetration in vitro, local delivery of horseradish peroxidase was performed in 40 porcine peripheral arteries, and delivery of fluoresceinated heparin was performed in 20 porcine peripheral arteries and 7 human atheromatous arteries. To determine the persistence of these agents in the vessel wall in vivo, horseradish peroxidase was delivered to 18 porcine peripheral arteries that were harvested at intervals of 45 min to 48 h. Fluoresceinated heparin was delivered to 22 porcine peripheral arteries, 14 with the use of a protective sleeve, harvested at intervals of 30 s to 24 h.

RESULTS

In vitro agent delivery was successful in all specimens. The depth of penetration of horseradish peroxidase was directly related to both balloon pressure (p < 0.04) and duration of inflation (p < 0.01). In vivo peroxidase staining was evident at 45 and 90 min but not thereafter. With the use of a protective sleeve, heparin was present in all arteries harvested at 30 s, with marked dissipation at 1 and 24 h. Without a sleeve, no fluorescein staining was detected in any artery. With both agents, delivery occurred consistently over broad regions of the vessel wall that were free of architectural disruption.

CONCLUSIONS

Hydrogel-coated balloons can deliver biologically active agents to the vessel wall without gross tissue disruption and may provide an atraumatic method for the local delivery of therapeutic agents during balloon angioplasty.

In vivo radiofrequency thermal balloon angioplasty of porcine coronary arteries: histologic effects and safety

The purpose of this study was to assess the safety and histologic effects of radiofrequency thermal balloon angioplasty in the coronary vasculature of normal pigs. Radiofrequency thermal balloon angioplasty was performed in 30 coronary arteries of 16 nonatherosclerotic pigs. Heated inflations were performed at either 50 degrees, 60 degrees, or 70 degrees C for 30 or 60 seconds, and were compared with five nonheated inflations in five additional arteries. All balloon inflations were performed at 2 atm pressure with a balloon/vessel diameter ratio of 1.2 to 1. Heart rate, arterial pressure, and left ventricular pressure were monitored continuously for each animal. A 12-lead ECG, coronary angiography, and two-dimensional transthoracic echocardiography were performed before and 1 hour after each balloon inflation. Each animal was subsequently put to death for postmortem cardiac examination. Heated inflations were well tolerated in 28 of the 30 arteries without significant adverse effects. During one inflation, ventricular fibrillation occurred because of prolonged ischemia from an occlusive guiding catheter. In another artery, a heated inflation resulted in a dissection with a transient decrease in distal coronary flow. Histologic examination revealed a significant increase in wall thinning and elastic fiber straightening with heating at 70 degrees C for both 30 and 60 seconds, and a significant increase in intracoronary thrombus with heating at 70 degrees C for 60 seconds. Depth of periarterial myocardial heat necrosis paralleled the increase in temperature, with an average depth of 166 microns at 50 degrees C, 312 microns at 60 degrees C, and 1031 microns at 70 degrees C. In vivo, radiofrequency coronary angioplasty can be performed relatively safely without significant electrical, hemodynamic, or ischemic changes beyond those seen with conventional nonthermal angioplasty. The extent of heat-induced vessel wall thinning, elastic tissue straightening, intracoronary thrombus formation, and periarterial myocardial necrosis are all related to balloon temperature or duration of heating.

Intracardiac echocardiography in humans using a small-sized (6F), low frequency (12.5 MHz) ultrasound catheter. Methods, imaging planes and clinical experience

OBJECTIVES

This study was designed to determine the clinical utility and feasibility of using 12.5-MHz ultrasound catheters for intracardiac echocardiography.

BACKGROUND

Intracardiac echocardiography is a potentially useful technique of cardiac imaging and monitoring in certain settings. The feasibility of intracardiac echocardiography using 20-MHz ultrasound catheters in patients has been demonstrated. High resolution images of normal cardiac structures as well as cardiac abnormalities have been obtained. However, imaging has been limited by the shallow depth of field inherent in high frequency ultrasound imaging.

METHODS

Intracardiac echocardiography with 12.5-MHz catheters was performed in eight mongrel dogs and 92 patients. Catheters were introduced percutaneously in 80 patients studied in the catheterization laboratory and directly into the heart in 12 patients in the operating room. Right heart imaging was performed in 68 patients and arterial and left heart imaging in 35 patients.

RESULTS

When these catheters were introduced into the venous system, the right atrium, tricuspid valve, right ventricle, pulmonary valve and pulmonary artery were visualized. Pericardial effusion, intracardiac masses and atrial septal defects were correctly identified. The left ventricle, left atrium, mitral valve, aortic valve, aorta and coronary arteries could be imaged from the arterial circulation. Diseases identified included valvular aortic stenosis, subvalvular aortic stenosis and Kawasaki disease. Average imaging time was 10 min. No complications occurred as a result of intracardiac echocardiography.

CONCLUSIONS

Intracardiac echocardiography with 12.5-MHz ultrasound catheters is safe and feasible; it also provides anatomic and physiologic information. This feasibility study provides a foundation for wider clinical use of intracardic echocardiography.

Predictors of long-term outcome after percutaneous balloon mitral valvuloplasty

BACKGROUND

Percutaneous balloon mitral valvuloplasty is known to produce short-term hemodynamic and symptomatic improvement in many patients with mitral stenosis. Comprehensive assessment of the clinical usefulness of balloon valvuloplasty requires evaluation of patients' long-term outcomes.

METHODS

We performed balloon mitral valvuloplasty in 146 patients between October 1, 1985, and October 1, 1991. Base-line demographic, clinical, echocardiographic, and hemodynamic variables were evaluated in order to identify predictors of long-term event-free survival.

RESULTS

Balloon mitral valvuloplasty was completed successfully in 136 (93 percent) of the patients in whom the procedure was attempted; it resulted in an increase in the mean (+/- SD) mitral-valve area from 1.0 +/- 0.4 to 2.1 +/- 0.9 cm2 and a decrease in the mean transmitral pressure gradient from 14 +/- 5 to 6 +/- 3 mm Hg (P < 0.001 for both comparisons). The estimated overall five-year survival rate was 76 +/- 5 percent, and the estimated five-year event-free survival rate (the percentage of patients without mitral-valve replacement, repeat valvuloplasty, or death from cardiac causes) was 51 +/- 6 percent. According to multivariate Cox proportional-hazards analysis, the independent predictors of longer event-free survival were a lower mitral-valve echocardiographic score (a measure of mitral-valve deformity; range, 0 for a normal valve to 16 for a seriously deformed valve; P < 0.001), lower left ventricular end-diastolic pressure (P = 0.001), and a lower New York Heart Association (NYHA) functional class (P = 0.04). Patients with no risk factors for early restenosis or only one risk factor (echocardiographic score > 8, left ventricular end-diastolic pressure > 10 mm Hg, or NYHA functional class IV) had a predicted five-year event-free survival rate of 60 to 84 percent, whereas patients with two or three risk factors had a predicted five-year event-free survival rate of only 13 to 41 percent.

CONCLUSIONS

Balloon mitral valvuloplasty as a treatment for selected patients with mitral stenosis has good long-term results. The long-term outcome after this procedure can be predicted on the basis of patients' base-line characteristics.

Immediate results and long-term follow-up after repeat balloon aortic valvuloplasty

Balloon aortic valvuloplasty (BAV) was performed in 219 elderly patients with aortic stenosis between December 1985 and April 1990. Forty-three patients underwent repeat BAV for symptomatic restenosis of the aortic valve 13 +/- 8 mo following initial BAV. To evaluate the outcome following initial and repeat BAV, hemodynamic results were analyzed according to the following subgroups: BAV 1--initial BAV for all patients (n = 219); BAV 1/1--initial BAV in those who had only one BAV (n = 176); BAV 1/2--the initial BAV in those who had repeat BAV (n = 43); and BAV 2--repeat BAV (n = 43). The mean age of patients undergoing BAV 2 was 82 +/- 6 yr compared to 78 +/- 10 yr for all patients undergoing BAV 1 (p = .01). At the time of BAV 1 there was no difference in baseline or post-valvuloplasty aortic valve area (AVA) or peak aortic valve gradient (AVG) for patients having BAV 1/1 compared to those having BAV 1/2. However, for patients having repeat BAV, although the magnitude of the hemodynamic improvement of BAV 1/2 (AVA increased from 0.6 to 0.9 cm2, AVG decreased from 68 to 34 mm Hg, p less than .001) was similar to the magnitude of the hemodynamic improvement of BAV 2 (AVA increased from 0.5 to 0.8 cm2, AVG decreased from 65 to 34 mm Hg, p less than .001), the baseline AVA (0.5 cm2 at BAV 2 vs. 0.6 at BAV 1/2) and the post-valvuloplasty AVA (0.8 cm2 at BAV 2 vs. 0.9 at BAV 1/2) were significantly smaller (p less than .004).(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic evaluation of a chronically implanted, electrically powered left ventricular assist system: responses to acute circulatory stress

Hemodynamic stress testing was performed in four calves with a chronically implanted left ventricular assist device consisting of a double-valved pump interposed between the left ventricular apex and the descending thoracic aorta. The device was powered either pneumatically (n = 1) or with a transcutaneous energy transmission system (n = 3). Hemodynamic evaluation (cardiac output and right and left ventricular and pulmonary and carotid artery pressures) was carried out at baseline and during all hemodynamically stressed states. Atrial pacing and ventricular pacing to a heart rate of 140 beats/min resulted in no significant change in right or left heart filling pressures or cardiac output. Preload reduction with nitroprusside or transient inferior vena cava balloon occlusion resulted in a marked decrease in left ventricular pressure with preservation of mean arterial pressure. Phenylephrine administration resulted in a marked rise in mean arterial pressure with no change in cardiac output or filling pressure. Induction of ventricular fibrillation resulted in a decrease of mean left ventricular pressure to 11 +/- 8 mm Hg, but mean arterial pressure was maintained at greater than or equal to 50 mm Hg. It is concluded that a multicomponent, implantable, electrically powered assist system is capable of maintaining a normal cardiac output under a wide range of loading conditions and chronotropic states. Although this device is clearly preload dependent, it is capable of maintaining normal systemic pressures during conditions of severe left ventricular dysfunction and circulatory collapse.

Predictors of event-free survival after balloon aortic valvuloplasty

BACKGROUND

Balloon aortic valvuloplasty was developed as an alternative to aortic-valve replacement in selected elderly patients with aortic stenosis. The use of this procedure is limited, however, by a high incidence of restenosis.

METHODS

Between December 1985 and April 1989, valvuloplasty was performed in 205 patients. We evaluated 40 demographic and hemodynamic variables as univariate predictors of event-free survival by Cox regression analysis and identified independent predictors of event-free survival by stepwise multivariate analysis.

RESULTS

Early hemodynamic results indicated a decrease in the peak transaortic-valve pressure gradient from 67 +/- 28 to 33 +/- 15 mm Hg after valvuloplasty and an increase in aortic-valve area from 0.6 +/- 0.2 to 0.9 +/- 0.3 cm2 (P less than 0.001 for both comparisons). The rate of event-free survival (defined as survival without recurrent symptoms, repeated valvuloplasty, or aortic-valve replacement) was 18 percent over the mean (+/- SD) follow-up period of 24 +/- 12 months (range, 1 to 47). Significant predictors of event-free survival included the left ventricular ejection fraction and the left ventricular and aortic systolic pressure before valvuloplasty, and the percent reduction in the aortic-valve pressure gradient; the pulmonary-capillary wedge pressure was inversely associated with event-free survival. Although the predicted event-free survival rate for the entire patient group was 50 percent at one year (95 percent confidence interval, 43 to 57 percent) and 25 percent at two years (95 percent confidence interval, 19 to 31 percent), the probability of event-free survival at one year varied between 23 and 65 percent when patients were stratified according to three independent predictors: the aortic systolic pressure, the pulmonary-capillary wedge pressure, and the percent reduction in the peak aortic-valve gradient.

CONCLUSIONS

The most important predictors of event-free survival after balloon aortic valvuloplasty were related to base-line left ventricular performance. The best long-term results after valvuloplasty were observed among patients who would also have been expected to have excellent long-term results after aortic-valve replacement.

Real-time, intracardiac, two-dimensional echocardiography: enhanced depth of field with a low-frequency (12.5 mhz) ultrasound catheter

Advances in catheter-based ultrasound imaging technology allow for a unique opportunity to develop two-dimensional intracardiac echocardiography, an imaging method that could have significant clinical applications. In this study, we evaluated the potential of a new, percutaneous, 9-Fr prototype intracardiac echocardiographic catheter with a 12.5-MHz rotating crystal in 13 dogs. In all dogs, we were able to easily advance the intracardiac echocardiographic catheter into the right and left hearts percutaneously and obtain dynamic images of cardiac structures in various imaging planes. With the intracardiac echocardiographic catheter in the right atrium, the whole chamber could be visualized. Minor manipulation allowed visualization of the right atrium, right ventricle, and tricuspid valve in a two-chamber view; further maneuvering yielded four-chamber views. With advancement of the catheter into the right ventricle and pulmonary artery, the right ventricular cavity, right ventricular outflow tract, and pulmonary artery could be imaged. The intracardiac echocardiographic catheter in the aortic root allowed visualization of the pulmonary artery and its bifurcation, superior portions of the atria, interatrial septum, aortic valve, and the proximal left coronary artery. With the intracardiac echocardiographic catheter in the left ventricle, short-axis images of the whole left ventricle were obtained. Manipulating the catheter tip within the left ventricle, we could visualize the left ventricle, left atrium (LA), and the mitral valve in the long axis. We were also able to visualize and identify experimentally-induced ischemic regional left ventricular dyskinesis (four of of five dogs), aortic valvular tear (five out of five dogs), and pericardial effusion with right atrial collapse (two out of two dogs). Intracardiac echocardiography was not associated with any complications. We conclude that percutaneous, low-frequency intracardiac echocardiography with a 12.5-MHz, 9-Fr catheter yields cardiac images in many imaging planes with a good depth of field, allows identification of valvular, myocardial, and pericardial abnormalities, and has excellent clinical potential in the assessment of many cardiovascular disorders.

The Mansfield Scientific Aortic Valvuloplasty Registry: overview of acute hemodynamic results and procedural complications

Between December 1, 1986 and October 30, 1987, balloon aortic valvuloplasty was performed in 492 patients with aortic stenosis (mean age 79 +/- 8.4 years) enrolled in the Mansfield Scientific Aortic Valvuloplasty Registry. All procedures were performed from a femoral approach (92%), brachial approach (6%) or transseptal approach (2%) and utilized either a single balloon technique (72%) or a double balloon technique (28%). Valvuloplasty resulted in a significant improvement in aortic valve area (0.50 +/- 0.18 cm2 to 0.82 +/- 0.30 cm2), mean aortic valve gradient (60 +/- 23 mm Hg to 30 +/- 13 mm Hg) and cardiac output (3.86 +/- 1.26 to 4.05 +/- 1.31 liters/min). Serial aortography demonstrated a moderate or severe increase in aortic insufficiency in only 2.1% of patients. Statistical analysis of the procedural factors affecting acute valvuloplasty results demonstrated significant correlations of single versus double balloon technique, total number of balloon inflations and total number of balloon exchanges with respect to the absolute change in mean aortic valve gradient occurring during the valvuloplasty procedure. In addition, there was a significant correlation between the maximal time of valvuloplasty balloon inflation with aortic valve area measured after valvuloplasty, and there were significant correlations of the total number of balloon inflations and total number of balloon exchanges with the aortic valve mean gradient measured after valvuloplasty. The overall complication rate for the procedure was 20.5%, including vascular injury in 11%, embolic phenomenon in 2.2%, ventricular perforation resulting in tamponade in 1.8%, massive aortic insufficiency in 1%, nonfatal arrhythmia in 0.8% and myocardial infarction in 0.2%.(ABSTRACT TRUNCATED AT 250 WORDS)

Serial assessment of mitral regurgitation by pulsed Doppler echocardiography in patients undergoing balloon aortic valvuloplasty

Mitral regurgitation was serially assessed by pulsed Doppler echocardiography in 144 patients undergoing balloon aortic valvuloplasty for symptomatic aortic stenosis. Regurgitant scores of 0, 1, 2 and 3 were assigned to pulsed Doppler patterns corresponding to no, mild, moderate and severe mitral regurgitation, respectively. Before balloon aortic valvuloplasty, mitral regurgitant score correlated significantly (p less than 0.005) but weakly with aortic valve area (r = -0.24), left ventricular ejection fraction (r = -0.34) and left ventricular systolic pressure (r = 0.23). There was no significant correlation between mitral regurgitation and either mean catheterization or mean Doppler aortic valve gradient. Balloon aortic valvuloplasty produced significant decreases in both catheterization and Doppler mean transvalvular aortic valve gradients (56 +/- 19 to 31 +/- 12 and 60 +/- 19 to 48 +/- 16 mm Hg, respectively; both p less than 0.0001) and a significant increase (p less than 0.0001) in aortic valve area assessed by catheterization (0.6 +/- 0.2 to 0.9 +/- 0.3 cm2). Left ventricular ejection fraction did not change, but cardiac output increased (p less than 0.001) and pulmonary capillary wedge pressure decreased (p less than 0.0001). Pulsed Doppler findings of mitral regurgitation were present in 102 of the 144 patients. Eighty-eight patients had a score compatible with mild or more severe degrees of mitral regurgitation, and 49 had a score indicative of moderate or severe valvular insufficiency. In the entire group of 144 patients, mitral regurgitant score decreased significantly from 1.1 +/- 1.0 to 1.0 +/- 1.0 (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Progressive improvement in pulmonary vascular resistance after percutaneous mitral valvuloplasty

Percutaneous mitral valvuloplasty has been proposed as a nonsurgical technique for treating high-risk patients with mitral stenosis who are deferred from mitral valve replacement. The effect of this technique on patients with pulmonary hypertension, however, has not been fully evaluated. Accordingly, serial assessment of pulmonary vascular resistance was made in 14 patients with critical mitral stenosis and pulmonary hypertension (pulmonary vascular resistance greater than 250 dynes.sec/cm5 or mean pulmonary artery pressure greater than 40 mm Hg or both) who underwent percutaneous balloon dilatation of the mitral valve. Balloon valvuloplasty was performed with either one (n = 10) or two (n = 4) balloons through the transseptal approach, and it resulted in significant improvement in mean mitral gradient (from 18 +/- 4 to 9 +/- 4 mm Hg, p less than 0.001), systemic blood flow (from 3.7 +/- 1.2 to 5.0 +/- 2.2 l/min, p less than 0.001), and calculated mitral valve area (from 0.7 +/- 0.2 to 1.6 +/- 0.7 cm2, p less than 0.001). Immediately after balloon mitral valvuloplasty, pulmonary vascular resistance fell from 630 +/- 570 to 447 +/- 324 dynes.sec/cm5. Repeat catheterization 7 +/- 4 months after valvuloplasty showed further improvement of pulmonary hypertension in 12 of the 14 patients, with a mean pulmonary vascular resistance for the group as a whole of 280 +/- 183 dynes.sec/cm5, p less than 0.005. In two patients, mitral valve restenosis to a mitral valve area less than 1.0 cm2 was associated with a return of pulmonary hypertension to predilatation values.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of right atrial pressure-volume relations in patients with and without an atrial septal defect

Assessment of the complex relations between pressure and volume in the right atrium has been hampered in the past by difficulties in the measurement of atrial volume. Accordingly, in the present study the dynamics of right atrial pressure-volume relations were examined (with the use of an impedance catheter to measure right atrial volume) in patients with and without an atrial septal defect. Right atrial pressure and impedance volume were measured in 16 patients at the time of cardiac catheterization with the use of a multi-electrode impedance catheter to provide continuous, on-line, pressure-volume data. Eleven patients without evidence of an interatrial shunt were examined during normal respiration and during the Valsalva maneuver and contrasted with five patients with an atrial septal defect documented by oxygen saturation step-up and echocardiographic studies. Right atrial pressure-volume diagrams in patients without an atrial septal defect exhibited the normal figure eight pattern, with an A loop (atrial contraction) and a V loop (passive filling), corresponding to the A wave and V wave of right atrial pressure, respectively. During inspiration, mean right atrial pressure decreased and mean right atrial volume increased, consistent with augmented venous return. With the Valsalva maneuver, right atrial pressure increased and both right atrial stroke volume and mean right atrial volume decreased compared with baseline. Patients with an atrial septal defect demonstrated baseline pressure-volume diagrams similar to those of patients without an interatrial shunt. However, no change in mean right atrial volume occurred with either respiration or the Valsalva maneuver despite changes in right atrial pressure similar to those seen inpatients without an atrial septal defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of respiration and vasodilation on venous volume in animals and man, as measured with an impedance catheter

Venous return determines cardiac preload and is in turn affected by respiration and vasodilation. The purpose of the present study was to examine the dynamics of venous return and venous volume, using impedance volume measurements in the venous system. In order to develop a methodology for the assessment of venous volume and venous return in man, we first studied 17 endotracheally intubated and ventilated anesthetized closed-chest dogs. We measured central venous and inferior vena cava (IVC) pressure (micromanometer) and volume (impedance catheter). Studies were done above and below the diaphragm with normal ventilation, with positive end-expiratory pressure (PEEP), and with beta-adrenergic blockade and i.v. nitroglycerin. Intrathoracic IVC volume fell and extrathoracic IVC volume rose with lung inflation, while PEEP raised extrathoracic IVC volume and lowered intrathoracic IVC volume. Nitroglycerin lowered intrathoracic IVC volume. Beta blockade did not affect IVC volume, ventilatory variation, or response to PEEP and nitroglycerin. We performed similar studies in 14 human subjects during normal quiet respiration, with measurements above and below the diaphragm, and with interventions including Valsalva maneuver and i.v. nitroglycerin. Intrathoracic IVC volume fell and extrathoracic IVC volume rose with expiration and Valsalva maneuver. Nitroglycerin again lowered intrathoracic IVC volume. We conclude that venous volume and the dynamics of venous return can be assessed in animals and man with an impedance catheter. Specifically, we show the divergent effects of respiration, ventilation, PEEP, and nitroglycerin on IVC volumes above and below the diaphragm. Beta-adrenergic blockage does not appear to play a role in altering any of these effects.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of nitroprusside to characterize aortic pressure-diameter relationships

The viscoelastic properties of the wall of the ascending aorta can be determined by calculating the relationship between pressure and diameter of the vessel. Because of potential nonlinearities in aortic pressure-diameter relationships, however, pressure-diameter curves are more accurate than compliance expressed as a single value in measuring aortic viscoelastic properties. To determine whether nitroprusside could be used to obtain aortic pressure-diameter curves over a wide range, we measured simultaneous aortic pressure and diameter in anesthetized dogs. The inferior vena cava (IVC) of each animal was briefly occluded to generate a baseline series of pressure-diameter points over a wide range of pressure and diameter. We found that moderate lowering of systolic arterial pressure (30 mmHg) with nitroprusside did not significantly affect the aortic pressure-diameter relationship in comparison with control measurements during brief IVC occlusions at similar pressures and diameters. Prolonged inferior vena caval occlusion and a more profound lowering of arterial pressure with nitroprusside or IVC occlusion resulted in a leftward and upward shift of the aortic pressure-diameter relationship, with higher pressures at comparable diameters and lower diameters at comparable pressures. However, with more profound changes in arterial pressure, possible reflex-mediated mechanisms that alter the baseline aortic pressure-diameter relationship may be activated. We conclude that nitroprusside can be used to obtain aortic pressure-diameter data over a wider range than that possible from a single cardiac cycle.

Current complications of diagnostic and therapeutic cardiac catheterization

Data from 2,883 cardiac catheterizations performed during an 18 month period (from July 1986 through December 1987) were analyzed to assess the current complication profile of diagnostic and therapeutic procedures. Procedures performed during the study period included 1,609 diagnostic catheterizations, 933 percutaneous transluminal coronary angioplasties and 199 percutaneous balloon valvuloplasties. Overall, the mortality rate was 0.28% but ranged from 0.12% for diagnostic catheterizations to 0.3% for coronary angioplasty and 1.5% for balloon valvuloplasty. Emergency cardiac surgery was required in 12 angioplasty patients (1.2%). Cardiac perforation occurred in seven patients (0.2%), of whom six were undergoing valvuloplasty, and five (2.5% of valvuloplasty attempts) required emergency surgery for correction. Local vascular complications requiring operative repair occurred in 1.9% of patients overall, ranging from 1.6% for diagnostic catheterization to 1.5% for angioplasty and 7.5% for valvuloplasty. Although the complication rates for diagnostic catheterization compare favorably with those of previous multicenter registries, current overall complication rates are significantly higher because of the performance of therapeutic procedures with greater intrinsic risk and the inclusion of increasingly aged and acutely ill or unstable patients.

Depression of systolic and diastolic myocardial reserve during atrial pacing tachycardia in patients with dilated cardiomyopathy

Previous reports have shown that increases in heart rate may result in enhanced left ventricular (LV) systolic and diastolic performance. To assess whether this phenomenon occurs in the presence of depressed LV function, the effects of pacing on LV pressure and volume were compared in seven patients with dilated cardiomyopathy (LV ejection fraction 0.19 +/- 0.11) and six patients with no or minimal coronary artery disease (LV ejection fraction 0.69 +/- 0.11). Patients with normal LV function demonstrated significant increases in LV peak-positive dP/dt, LV end-systolic pressure-volume ratio, LV peak filling rate, and a progressive leftward and downward shift of their pressure-volume diagrams, compatible with increased contractility and distensibility in response to pacing tachycardia. There was no change in LV peak-negative dP/dt or tau. Patients with dilated cardiomyopathy, in contrast, demonstrated no increase in either LV peak-positive dP/dt or the end-systolic pressure-volume ratio, and absence of a progressive leftward shift of their pressure-volume diagrams. Moreover, cardiomyopathy patients demonstrated no increase in LV peak-negative dP/dt or LV peak filling rate and a blunted downward shift of the diastolic limb of their pressure-volume diagrams. Tau, as determined from a derivative method, became abbreviated although never reaching control values. We conclude that patients with dilated cardiomyopathy may demonstrate little or no significant enhancement in systolic and diastolic function during atrial pacing tachycardia, suggesting a depression of both inotropic and lusitropic reserve.