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Biomedical subjects

M S Chang

Publications and source records attributed to M S Chang.

At least 307 records · Page 17Linked to original sources
PubMed1992

Reduced left ventricular compliance in human mitral stenosis. Role of reversible internal constraint.

BACKGROUND: The mechanisms of depressed left ventricular (LV) pump performance in human mitral stenosis (MS) remain poorly understood, because reduced filling alone affects many hemodynamic measurements. Therefore, pressure-volume relations were examined in nine subjects with MS and compared with eight age-matched normal controls. METHODS AND RESULTS: Data were obtained by conductance catheter/micromanometer technique with transient inferior vena cava occlusion used to alter load and generate pressure-volume relations. In a subset of patients (n = 5), data were obtained both acutely and at 3 months (n = 4) after balloon valvuloplasty. MS patients had reduced cardiac output (3.3 +/- 0.9 versus 5.6 +/- 1.7 l/min) and end-diastolic volume (68.0 +/- 6.9 versus 115 +/- 31 ml) versus controls (p less than 0.001), with a mean transvalvular gradient of 14 +/- 6 mm Hg and estimated valve area of 0.6 +/- 0.2 cm2. Systolic function as assessed by the end-systolic pressure-volume relation was virtually the same in MS and control subjects. In contrast, end-diastolic pressure-volume relations in MS were consistently shifted leftward and had an increased slope (lower compliance) at matched pressure ranges (6.5 +/- 3.0 versus 2.2 +/- 0.53 ml/mm Hg at a mean diastolic pressure of 8 mm Hg, p less than 0.001). This change was not a result of reduced LV filling or probably of increased right heart loading. Valvuloplasty acutely returned chamber compliance to near normal, a change that was sustained at 3-month follow-up. Systolic function was little altered at this time. CONCLUSIONS: These data indicate an impairment of diastolic function in human MS that can be acutely reversed by balloon valvuloplasty. Lowered LV compliance probably results from a functional restriction caused by ventricular attachment to a thickened and immobile valve apparatus.

Cardiac Catheterization↗
PubMed1992

Effective arterial elastance as index of arterial vascular load in humans.

BACKGROUND: This study tested whether the simple ratio of ventricular end-systolic pressure to stroke volume, known as the effective arterial elastance (Ea), provides a valid measure of arterial load in humans with normal and aged hypertensive vasculatures. METHODS AND RESULTS: Ventricular pressure-volume and invasive aortic pressure and flow were simultaneously determined in 10 subjects (four young normotensive and six older hypertensive). Measurements were obtained at rest, during mechanically reduced preload, and after pharmacological interventions. Two measures of arterial load were compared: One was derived from aortic input impedance and arterial compliance data using an algebraic expression based on a three-element Windkessel model of the arterial system [Ea(Z)], and the other was more simply measured as the ratio of ventricular end-systolic pressure to stroke volume [Ea(PV)]. Although derived from completely different data sources and despite the simplifying assumptions of Ea(PV), both Ea(Z) and Ea(PV) were virtually identical over a broad range of altered conditions: Ea(PV) = 0.97.Ea(Z) + 0.17; n = 33, r2 = 0.98, SEE = 0.09, p less than 0.0001. Whereas Ea(PV) also correlated with mean arterial resistance, it exceeded resistance by as much as 25% in older hypertensive subjects (because of reduced compliance and wave reflections), which better indexed the arterial load effects on the ventricle. Simple methods to estimate Ea (PV) from routine arterial pressures were tested and validated. CONCLUSIONS: Ea(PV) provides a convenient, useful method to assess arterial load and its impact on the human ventricle. These results highlight effects of increased pulsatile load caused by aging or hypertension on the pressure-volume loop and indicate that this load and its effects on cardiac performance are often underestimated by mean arterial resistance but are better accounted for by Ea.

Adult↗
PubMed1992

Safety and efficacy of a modified catheter-mediated ablation of accessory pathways.

Fifty-one consecutive patients underwent modified catheter-mediated direct-current ablation of accessory pathways. Energy was delivered through the distal pair of electrodes (dual electrode configuration) of a 6F quadripolar catheter to the internal surface of the right or left atrioventricular (AV) annulus. In an attempt to prevent the later resumption of accessory pathway conduction, one additional shock was given after the initial successful interruption of accessory pathways. A mean of 2.7 shocks with cumulative energy of 453 +/- 32 Joules/patient interrupted the accessory pathways in 47 patients and modified the accessory pathway conduction in 2 patients. Forty-eight patients were asymptomatic and free of any antiarrhythmic agents with a follow-up ranging from 3-20 months (mean 12 +/- 1 months), without early or late serious complications (AV block or tamponade). Conduction characteristics, concealed or manifest, and recording of accessory pathway activity did not affect the outcome. Mean cumulative energy and number of applications of energy to achieve a successful outcome were lower in patients with concealed (376 +/- 31 Joules, 2.4 +/- 0.2 shocks) than manifest accessory pathways (516 +/- 50 Joules, 2.9 +/- 0.2 shocks). At the successful ablation sites, the mean shortest retrograde ventriculoatrial interval during orthodromic reentrant tachycardia (VA') was 80 +/- 3 msec (78% had VA' less than 90 msec) and was not different between concealed and manifest accessory pathways; the mean shortest antegrade AV interval was 47 +/- 3 msec in manifest preexcitation; the mean ratio of atrial to ventricular wave amplitude was not significantly different between left-sided (0.8 +/- 0.1) and right-sided (1.1 +/- 0.2) accessory pathways (p greater than 0.05). A successful outcome was achieved in 94% of 51 patients. This procedure is relatively safe and effective, regardless of the location of the accessory pathway.

Adult↗
PubMed1992

A comparative study of a modified catheter-mediated direct current and radiofrequency ablation on atrioventricular junction.

Conventional His-bundle ablation, performed at the site with the largest His-bundle potential, displays a high incidence of a new right bundle branch block with loss of pacemaker escape. Damage to the perinodal atrial area may decrease the injury to the His-bundle, such that the escape pacemaker activity with a narrow QRS complex is produced. This study reports data from 25 patients with drug-refractory atrial tachyarrhythmias. Nine patients (group I) received radiofrequency (RF) ablation of the atrioventricular junction (AVJ). General anesthesia was not necessary in group I patients. During a mean follow-up period of 10 months, a complete AV block persisted in 5 patients, and a first degree AV block persisted in 2 patients; these patients were asymptomatic and did not require treatment with antiarrhythmic agents. A successful direct-current (DC) ablation was performed in one of the patients with an unsuccessful RF lesion, producing a new right bundle branch block (RBBB). Sixteen patients (group II) received DC ablation of the AVJ. During a mean follow-up period of 20 months, a complete AV block persisted in 9 patients, a first degree AV block was produced in 7 patients, and a new RBBB occurred in 2 patients. Fifteen patients (94%) were asymptomatic without administration of antiarrhythmic agents. Complications, including nonsustained ventricular tachycardia (1 patient) and pericarditis (1 patient), occurred immediately after ablation in group II. Myocardial injury, reflected by creatine kinase-MB isoenzyme, was higher in group II than in group I (25 +/- 2 vs 10 +/- 1 IU/l). We conclude that (1) catheter-mediated RF ablation of the AV junction is safer than DC ablation, (2) a majority of patients with drug-refractory atrial tachyarrhythmias can be successfully treated with RF ablation and (3) failure to achieve AV junction ablation with RF does not mitigate against successful application of DC ablation.

Adult↗
PubMed1992

Quantitative analysis of the coronary angiograms.

This was a two-step study performed to assess the validity of a computer system in the quantification of coronary arterial angiography (CAG). First, the in vitro study involved 10 aluminum tubes in different internal diameters but the same thickness which were pre-filled with 76% urograffin followed by cinefilm taking. Acquisition and digitization of the stop film was undertaken by a videocamera linking to a computer system. The internal diameters and mean gray levels of all tubes were measured to compare with the real diameters and areas. Second, the in vivo study calculated the percentage of stenosis by visual estimation, diameter measurement and gray level measurement by the computer system from 22 vessels in 13 coronary angiograms. The percentage of patency is the ratio of the diameter or gray level from stenotic region to that of normal region in the CAG. The calculated interobserver variability by visual estimation, diameter measurement and Mean gray level measurement were studied. Good correlation was found between measured diameters and true tube diameters (r = 0.99), and between gray level and tube areas (r = 0.94). The diameter measured by computer and the gray level had lower variability (4.0% and 5.7% respectively) than visual estimation (9.8%) did. Thus, the diameter and densitometric gray level measurements might have clinical implications to assess the coronary arterial stenosis from the coronary angiograms.

Aged↗
PubMed1992

Delayed localized right atrial tamponade by intrapericardial hematoma after aortic valve replacement: a case report.

Cardiac tamponade, early or late after cardiac surgery, is an uncommon while a potentially lethal condition in which the classic signs of tamponade may be absent. High index of suspicion and rapid diagnosis are mandatory for life-saving decompressive therapy. We herein reported a case of delayed localized right atrial tamponade caused by loculated intrapericardial hematoma 26 days after aortic valve replacement, which was recognized immediately by transthoracic two-dimensional echocardiography. The clinical status improved dramatically after surgical removal of the hematoma.

Aged↗
PubMed1992

Response of left ventricular ejection performance following balloon valvuloplasty in patients with mitral stenosis.

In order to see if any change of left ventricular ejection performance (LEVP) would occur after successful balloon mitral valvuloplasty (BMV), a prospective study on echocardiography and calibrated carotid pulse tractings was performed two days before, two days and then six months after BMV in 24 patients with pure rheumatic mitral stenosis (MS). Echocardiographic parameters representing preload i.e. end-diastolic volume index (EDVI); afterload i.e. end-systolic wall stress (ESS), and the indices of LVEP i.e. ejection fraction (EF), fractional shortening, rate-corrected velocity of circumferential shortening (VCFc) and a ratio of ESS over end-systolic volume index (ESS/ESVI) were measured. A group of 66 normal subjects was used to establish the 95% confidence interval of the echo parameters. The incidence of depressed LVEP in MS patients was about 21% when measured by load-independent index i.e. ESS/ESVI. In the MS group, 7 out 24 (29%) patients achieved an increased cardiac index after BMV. Six (25%) MS patients showed an EF below 95% confidence interval of control (less than 55%) before BMV and, of these 6, only 3 patients increased their EDVI after the BMV. Those who showed an EF greater than or equal to 55% before BMV gave no change in their preload (EDVI) after the BMV. Only one MS patient showed high afterload (ESS) both before and after BMV. However, the ESS/ESVI showed insignificant improvement (p = 0.055) after BMV. It was therefore concluded that (1) a depressed LVEP is frequently seen in patients with MS; (2) LVEP can be improved by BMV in some (21%) patients with MS, and the improvement is not related to the change of preload or afterload but more likely secondary to an increased myocardial contractility.

Adult↗
PubMed1992

Long-term efficacy of percutaneous transluminal coronary angioplasty.

Percutaneous transluminal coronary angioplasty (PTCA) is a well-accepted procedure used in therapy for coronary artery stenosis. It is a delicate procedure depending upon the operator's experience and technique. Major efforts have been directed toward improving such performance. This is a report of our growing experience accumulated over the last eight years. From July 1983 to December 1990, 893 cases of coronary artery disease with a total of 1111 procedures received PTCA in this hospital. The success rate in dilatation increased year by year; to peak in 1990 (94%). PTCA was performed in 447 cases of single vessel disease; 310 cases of double vessels disease; and 136 cases of triple vessels disease. Dilated coronary artery lesions included left anterior descending artery, 637 (64%), right coronary artery, 198 (20%), and left circumflex artery 157 (16%). More than one procedure was undertaken in 178 patients, and about 20% patients had repeated PTCA. Major complications such as acute myocardial infarction developed in 3.0%. One point one percent had emergency surgery and the mortality rate was 1.8%. The majority of cases were followed up and appeared well after successful angioplasty. In conclusion, PTCA is an valuable procedure for treatment of critical coronary artery stenosis, with acceptable complications.

Adult↗
PubMed1992

[Comparison of nicardipine and nifedipine in treatment of Chinese senile hypertension placebo-control, double-blind, randomized and crossover study].

The purpose of this placebo-control, double-blind, randomized and crossover study is to evaluate the effect of nicardipine and nifedipine in Chinese senile hypertension. Among totally 37 senile hypertensive patients enrolled, 26 patients (25 males, 1 female) from 55 to 78 years of age (mean 65) who had finished one part or whole protocol were studied. Totally 18 cases after 6-week treatment of nicardipine (Perdipine) had blood pressure decrease significantly from 152.6 +/- 12.3/99.6 +/- 5.7 to 140.4 +/- 15.6/93.8 +/- 8.1 mmHg in supine position (P < 0.05), and from 153.3 +/- 12.7/98.7 +/- 7.7 to 139.2 +/- 13.5/90.7 +/- 7.6 mmHg in standing position (p < 0.05). Twenty-five cases after 6-week treatment of nifedipine (Towarat) also had significant blood pressure decrease from 155.0 +/- 13.3/99.5 +/- 8.4 to 144.2 +/- 10.0/95.3 +/- 9.2 mmHg in supine position (P < 0.05), and from 151.5 +/- 17.8/100.6 +/- 9.5 to 138.6 +/- 12.8/90.4 +/- 8.3 mmHg in standing position (p < 0.05). Heart rate was unchanged in both groups. Both nicardipine and nifedipine decreased blood pressure and increased heart rate significantly with the first dose of medication in the morning (P < 0.05). There was 6.5% and 9.0% decrease of systolic and diastolic blood pressure with nicardipine in supine position, 10.1% and 11.2% decrease with nifedipine in supine position, 6.3% and 7.2% decrease with nicardipine in standing position, and 9.7% and 10.6% decrease with nifedipine in standing position. The major side-effects were palpitation (20%) and lower abdominal distension (16%) with nicardipine; and nausea or vomiting (22%) and dizziness (15%) with nifedipine.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Follow-up of a modified catheter ablation of the atrioventricular junction in patients with atrial tachyarrhythmias.

In order to reduce cumulative energy, minimize barotrauma and infranodal injury, a modified catheter ablation technique was performed on seventeen patients. These patients had drug refractory atrial tachyarrhythmias (AT) consisting of thirteen with paroxysmal atrial fibrillation (PAf), three with sick sinus syndrome (SSS) with PAf, and one having SSS with rapid left atrial tachycardia. This technique, using the femoral approach, consisted of delivering a direct-current (DC) shock using a dual electrode configuration, to the ablation site adjacent the atrioventricular (AV) junction just before the disappearance of His deflection on the His bundle electrogram. After delivering 1-4 DV shock (mean 2.8) (cumulative energy 556 +/- 260 joules), 9 pts had first degree AV block (1st AVB) and 8 pts had complete AV block (CAVB). Only two pts had a right bundle branch block after ablation. During the clinical follow-up (15.4 +/- 2.7 months), sixteen pts were asymptomatic and were free of antiarrhythmic drugs. One pt was asymptomatic with quinidine which was ineffective before ablation. Pacemaker implantation was performed in 10 pts as a back-up for symptomatic SSS and CAVB. The results show this modified technique is relatively safe and effective.

Adult↗
PubMed1991

Frequency and severity of mitral regurgitation one year after balloon mitral valvuloplasty.

Mitral regurgitation (MR) was evaluated by Doppler echocardiography in 59 patients with mitral stenosis before, immediately after and 1 year after balloon mitral valvuloplasty (BMV). The severity of MR was graded on a scale from 1+ to 4+. Echocardiographic and hemodynamic variables were analyzed to study the potential factor(s) that might predict the long-term persistence of MR. Echocardiographic variables were mitral valve thickness and motion, subvalvular change, left atrial dimension, commissural calcification and effective balloon/mitral anular diameters. Hemodynamic variables were mitral pressure gradient, pulmonary arterial pressure, ejection fraction, mitral valve area index, age, gender and cardiac rhythm. Mitral valve area index increased from 0.9 +/- 0.5 to 1.5 +/- 0.8 cm2/m2 immediately after BMW, and to 1.4 +/- 0.3 cm2/m2 at 1 year follow-up (p less than 0.01). Immediately after BMV, MR grading did not change in 30 patients (51%), increased by 1+ in 23 patients (39%), by 2+ in 2 patients (3.3%) and by 3+ in 2 patients (3.3%), and decreased by 1+ in 2 others. At 1-year follow-up, only 1 patient with severe MR required valve replacement. Fifty-one patients (88%) had no change in the extent of MR (less than or equal to 1+) and 6 patients (10%) had a 1-grade decrease in their MR; only 1 patient had a 1-grade increase in MR. No clinical or hemodynamic variables or morphologic characteristics of the mitral valve could predict the development of significant MR after BMV. It is concluded that an increment in MR severity less than or equal to 2+ is frequently seen after BMV.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Electromechanical effects of angiotensin in human atrial tissues.

Effects of exogenous angiotensin I (AI) and angiotensin II (AII) on action potential and contractile force of isolated atrial trabeculae obtained at cardiac surgery were studied by means of a standard microelectrode technique. In trabeculae driven electrically at a cycle length of 1 s, AII (8.4 nM - 8.4 microM) increased the contractile force with a peak effect occurred near 0.84 microM. The inotropic effect of AII was markedly inhibited by 1 microM saralasin or 1 microM diltiazem. AI (0.65 nM - 6.5 microM) also induced positive inotropic effect in a concentration-dependent manner. This inotropic effect was decreased significantly after 3 microM captopril pretreatment. In trabeculae active spontaneously in normal Tyrode solution, AI and AII increased significantly rate of diastolic depolarization and spontaneous discharges as well as force of contraction. These chronotropic effects were inhibited by captopril and saralasin, respectively. Captopril (0.3 nM - 3 microM) or saralasin (0.001 - 1 microM) alone also induced dose-dependent negative chronotropic effects. The present findings suggest the existence of functional AII receptors in human atrial tissues. The stimulatory effects of angiotensin appear to be related to an increase in cellular calcium.

Action Potentials↗
PubMed1991

Termination of digitalis-induced ventricular tachycardias by clonidine involves central alpha 2-adrenoceptors in cats.

1. Effects of intravenous (i.v.) and intravertebral arterial (i.a.) administration of the alpha 2-adrenoceptor agonist, clonidine (Clon) and its antagonist, yohimbine (Yoh, 0.5 mg kg-1, i.v.; 0.05 mg kg-1, i.a.), on ventricular tachycardia (VT) induced by intravenous acetylstrophanthidin (AS) were studied in cats anaesthetized with intraperitoneal chloralose. 2. AS dose-dependently produced cardiac arrhythmias including complete atrioventricular conduction block (118 +/- 14 micrograms kg-1, i.v.), junctional tachycardia (128 +/- 20 micrograms kg-1, i.v.), multiform ventricular premature beats (157 +/- 21 micrograms kg-1, i.v.) and sustained VT (220 +/- 23 micrograms kg-1, i.v.). 3. Doses of Clon (i.v.) required for termination of VT following i.v. Yoh (62.9 +/- 5.2 micrograms kg-1) or i.a. Yoh (88.5 +/- 16.3 micrograms kg-1) were higher than those for termination of VT without Yoh administration (28.3 +/- 6.2 micrograms kg-1). Doses of Clon (i.a.) required for termination of VT without or with i.a. Yoh administration were 5.8 +/- 1.0 or 14.8 +/- 3.7 micrograms kg-1, respectively, and they were significantly different. 4. These experiments demonstrate that either i.v. or i.a. Yoh antagonizes the antiarrhythmic effect of Clon on AS-induced VT. Since small doses of Clon administered i.a. act predominantly on the central nervous system, we suggest that its antiarrhythmic effect is likely to be on central alpha 2-adrenoceptors in the central nervous system.

Animals↗
PubMed1991

Transesophageal color Doppler flow mapping of iatrogenic left-to-right interatrial shunting after percutaneous transluminal mitral valvotomy.

Characteristics of transesophageal color Doppler flow mapping of iatrogenic left-to-right interatrial shunts were assessed in 58 patients, 1 to 994 days after percutaneous transluminal mitral valvotomy. Transesophageal color Doppler flow mapping detected 22 cases of interatrial shunt whereas transthoracic two-dimensional echocardiography visualized only five interatrial septal defects. Five types of color Doppler flow patterns of interatrial shunts were found: type 1, a bluish jet passing through the interatrial septum into the right atrium with a small bluish proximal flow in the left atrium (50%); type 2, a bluish jet passing through the interatrial septum into the right atrium without a proximal flow (13.6%); type 3, a predominant bluish proximal flow in the left atrium passing through the interatrial septum with minimal flow entering into the right atrium (18.2%); type 4, an "en face" bluish jet in the right atrium (4.5%); and type 5, a "wall jet" with proximal flow adhering to and entering into the interatrial septum (13.6%). Oximetry demonstrated increased pulmonary-to-systemic flow ratio (range 1.07 to 3.32) in 11 patients (50%), which was significantly correlated with the maximal jet area derived from color Doppler flow mapping (r = 0.80, P = 0.001). Thus, transesophageal color Doppler flow mapping is useful in detection of left-to-right interatrial shunts after percutaneous transluminal mitral valvotomy, and recognition of the variable types of color flow mapping may further help identify these atypical interatrial shunts.

Adult↗
PubMed1991

Penile brachial index in impotent patients with coronary artery disease.

From March to July 1989, a total of 40 patients, who had received coronary catheterization, answered questionnaires concerning sexual potency. In those 30 patients with a diseased coronary artery, only 2 (6.6%) had no erectile dysfunction subjectively. On the contrary, 4 of 10 (40%) patients with angiographically proven normal coronary artery complained of erectile dysfunction. Penile Doppler ultrasonography was performed in 30 patients. The mean penile brachial index (PBI) of 8 patients with a normal coronary artery was 0.82 +/- 0.1, as compared with the diseased group, 0.73 +/- 0.1 (p = 0.05). When these patients were further divided into two groups by a PBI of greater or less than 0.65, there was also no significant difference in the degree of obstruction of the three main coronary arteries between these two groups. There was no correlation between PBI and obstruction of the left anterior descending artery (r = 0.316, p = 0.689). Most of the patients (93.4%) with an abnormal coronary artery had erectile dysfunction. Nevertheless a poor correlation was noted between the PBI and the severity of coronary artery obstruction. Our study suggests that it is hard to use PBI alone as a predictor of future major thromboembolic heart attack.

Coronary Artery Disease↗
PubMed1991

Arterial hemodynamics in human hypertension. Effects of adrenergic blockade.

BACKGROUND: Resistance, pulse wave velocity, and wave reflections have been shown to be increased in patients with essential hypertension compared with normotensive controls. These alterations are completely normalized by nitroprusside infusion but exacerbated during beta-adrenergic blockade, suggesting an enhanced smooth muscle tone that is in part modulated by adrenergically mediated vasodilation. The present study was performed to examine the extent to which this apparently enhanced smooth muscle tone is a result of alpha-adrenergically mediated vasoconstriction. METHODS AND RESULTS: Age-matched normotensive and hypertensive Chinese subjects were instrumented with catheter-tipped micromanometers and an electromagnetic flow velocity sensor positioned in the ascending aorta. Aortic impedance and wave reflection properties were obtained from Fourier analysis of the pressure and flow signals during baseline conditions, after beta-blockade with propranolol (0.15 mg/kg i.v.), and after alpha-blockade with intravenous phentolamine (range, 15-80 mg) that was sufficient to either normalize blood pressure or produce a pressure that could not be further lowered. Compared with normotensives, in the baseline state, hypertensives had elevated resistance (1,962 versus 1,268 dyne.sec/cm5, p less than 0.001), total power (1,893 versus 1,568 mW, p less than 0.08), reflected pressure wave component (25.6 versus 13.5 mm Hg, p less than 0.001), ratio of reflected to forward wave (0.65 versus 0.42, p less than 0.001), and pulse wave velocity as determined from the frequency of the first zero-crossing of impedance phase angle (4.6 versus 3.5 Hz, p less than 0.03). During combined alpha- and beta-adrenergic blockade, blood pressure decreased into the normal range (from 162/103 to 131/87 mm Hg) but was still somewhat higher than that in the normotensive subjects. Resistance (1,914 dyne.sec/cm5, p less than 0.03), reflected wave (19.5 mm Hg, p less than 0.01), and ratio of reflected to forward wave (0.61, p less than 0.001) were, however, persistently elevated above normal values. CONCLUSIONS: alpha-Adrenergically mediated vasoconstriction cannot account for all of the hemodynamic alterations seen in essential hypertension.

Adult↗
PubMed1991

Detection of acute myocardial infarction by evaluation of ultrasonic gray levels in dogs.

The study tested whether an experimental myocardial infarction can be detected from two-dimensional echocardiograms (2DE) by analysis of regional gray levels. The mid-left anterior descending coronary artery was ligated for 3 hours in 14 dogs (group 1) and for 5 hours in 6 dogs (group 2). 2DE were performed before, and after 3 and 5 hours of coronary artery ligation. The ultrasonic amplitude of the control and infarcted regions were obtained from digitized 2DE in the short axis view, at the mid-papillary muscle level. The mean gray levels (+/- SD) of the control and infarcted regions were compared during end-diastolic stop frames. After sacrifice, the hearts were cut into 1 cm thick slices and stained with 1% triphenyl tetrazolium chloride (TTC) solution. The myocardium was then studied by light microscopy. Computerized tomographic scans were also obtained in vitro from 3 hearts of both groups. There was no difference in mean gray levels of the control region during the experiments. However, in the region of wall motion abnormality (area of infarction), the mean gray levels increased from 49.9 +/- 3.5 (before ligation) to 62.0 +/- 7.4 (after 3 hours of ligation, p less than 0.005) in 10 group 1 dogs, but no differences were seen in mean gray levels (49.6 +/- 3.8 vs 50.4 +/- 4.0) in those without a myocardial infarction in 4 group 1 dogs; gray levels also increased from 50.4 +/- 2.9 (before ligation) to 58.6 +/- 6.1 (after 3 hours of ligation, p less than 0.05) and to 65.0 +/- 4.2 (after 5 hours of ligation, p less than 0.005) in group 2 dogs. The area of left ventricular asynergy corresponded precisely to the area of myocardial infarction, determined by both TTC staining and the computerized tomographic scans. The light microscopy of the infarcted area also demonstrated interstitial edema and polymorphonuclear cell infiltration.

Animals↗