Biomedical subjects

S C Siu

Publications and source records attributed to S C Siu.

At least 37 records · Page 2Linked to original sources

PubMed1999

Atrial arrhythmia after surgical closure of atrial septal defects in adults.

BACKGROUND: Atrial flutter and atrial fibrillation are causes of morbidity in adults with an atrial septal defect. In this study, we attempted to identify risk factors for atrial flutter and fibrillation both before and after the surgical closure of an atrial septal defect. METHODS: We searched for preoperative and postoperative atrial flutter or fibrillation in 213 adult patients (82 men and 131 women) who underwent surgical closure of atrial septal defects because of symptoms, a substantial left-to-right shunt (ratio of pulmonary to systemic blood flow, >1.5:1), or both at Toronto Hospital between 1986 and 1997. RESULTS: Forty patients (19 percent) had sustained atrial flutter or fibrillation before surgery. As compared with the patients who did not have atrial flutter or fibrillation before surgery, those who did were older (59+/-11 vs. 37+/-13 years, P<0.001) and had higher mean pulmonary arterial pressures (25.0+/-9.7 vs. 19.7+/-8.2 mm Hg, P=0.001). There were no perioperative deaths. After a mean follow-up period of 3.8+/-2.5 years, 24 of the 40 patients (60 percent) continued to have atrial flutter or fibrillation. The mean age of these patients was greater than that of the 16 who converted to sinus rhythm (P=0.02). New-onset atrial flutter or atrial fibrillation was more likely to have developed at follow-up in patients who were older than 40 years at the time of surgery than in those who were 40 or younger (5 of 67 vs. 0 of 106, P=0.008). Late events (those occurring more than one month after surgery) included stroke in six patients (all but one with atrial flutter or fibrillation, one of whom died) and death from noncardiac causes in two patients. Multivariate analysis showed that older age (>40 years) at the time of surgery (P=0.001), the presence of preoperative atrial flutter or fibrillation (P<0.001), and the presence of postoperative atrial flutter or fibrillation or junctional rhythm (P=0.02) were predictive of late postoperative atrial flutter or fibrillation. CONCLUSIONS: The risk of atrial flutter or atrial fibrillation in adults with atrial septal defects is related to the age at the time of surgical repair and the pulmonary arterial pressure. To reduce the morbidity associated with atrial flutter and fibrillation, the timely closure of atrial septal defects is warranted.

Adolescent↗

PubMed1999

Myocardial perfusion during warm antegrade and retrograde cardioplegia: a contrast echo study.

BACKGROUND: We evaluated distribution of warm antegrade and retrograde cardioplegia in patients undergoing coronary artery bypass grafting (CABG). METHODS: Myocardial perfusion was evaluated pre- and post-CABG using transesophageal echocardiography with injection of sonicated albumin microbubbles (Albunex) during warm antegrade and retrograde cardioplegia. The left ventricle (LV) was evaluated in five segments and the right ventricle (RV) was evaluated in two segments. Segmental contrast enhancement was graded as absent (score = 0), suboptimal or weak (score = 1), optimal or excellent (score = 2), or excessive (score = 3). RESULTS: Pre-CABG cardioplegic perfusion correlated weakly with severity of coronary artery stenoses (r = -0.331 and 0.276 for antegrade and retrograde cardioplegia, respectively). Antegrade cardioplegia administration resulted in 98% and 96% perfusion to the left ventricle pre- and post-CABG, respectively. Retrograde cardioplegic administration resulted in reduced LV perfusion, with 86% (p = 0.032 from antegrade) and 59% (p<0.001 from antegrade) pre- and post-CABG, respectively. The average LV perfusion score (mean +/- SEM) was greater with antegrade than retrograde cardioplegia both pre-CABG (1.93+/-0.04 vs. 1.53+/-0.11, p<0.001) and post-CABG (1.63+/-0.07 vs. 1.19+/-0.13, p = 0.004). RV perfusion was poor with both techniques pre-CABG, but improved significantly with antegrade cardioplegia post-CABG. CONCLUSIONS: We conclude that warm antegrade cardioplegia results in better left ventricular perfusion than warm retrograde cardioplegia. Right ventricular cardioplegic perfusion was suboptimal, but the best delivery was achieved with antegrade cardioplegia after coronary bypass. We therefore recommend construction of the saphenous vein graft to the right coronary artery early in the operative procedure.

Aged↗

PubMed1999

Outcome of previous tricuspid valve operation and arrhythmias in adult patients with congenital heart disease.

BACKGROUND: Tricuspid valve operation or replacement has been associated with high perioperative mortality and poor long-term results. The prevalence of atrial arrhythmias before and after operation in these patients is undefined. METHODS: We retrospectively examined the outcome and frequency of atrial arrhythmias in 85 adult patients (46% men) with congenital heart defects who underwent tricuspid valve operation between 1961 and 1995. RESULTS: The majority had either Ebstein's anomaly (22%), congenitally corrected transposition (19%), tetralogy of Fallot (15%), atrial (13%), or ventricular (11%) septal defects. Forty-two (49%) patients had sustained arrhythmias within 1 year before operation. After tricuspid valve operation, 21 patients (50%) had recurrence of atrial arrhythmias, and 7 in preoperative sinus rhythm developed late rhythm disturbances. Multivariate analysis identified age at operation and preoperative arrhythmias as independent predictors of late arrhythmias. Perioperative mortality was 5%, and there were seven late deaths. Survival was 91% at 5 years, and 83% at 10 years. CONCLUSIONS: Surgical intervention does not prevent recurrence of atrial arrhythmias. Tricuspid valve operation in patients with congenital heart disease can be performed with a low risk of perioperative mortality and good long-term outcome.

Adolescent↗

PubMed1999

Outpatient clinics for adults with congenital heart disease: increasing workload and evolving patterns of referral.

OBJECTIVE: To examine the evolving role of specialised outpatient services for adult patients with congenital heart disease. DESIGN: A retrospective analysis of all patients attending the Toronto Congenital Cardiac Centre for Adults over three corresponding three month periods in 1987, 1992, and 1997. SETTING: A tertiary referral centre. MAIN OUTCOME MEASURES: Patient demographics, residence, medical and surgical history, type and source of referral, and investigations performed. RESULTS: In all, 570 patients were seen at the clinic during these three periods. There was a 44% and a 269% increase in workload between 1987 to 1992 and 1992 to 1997, respectively. There was a steady fall in mean age of patients seen at the clinic with time (38.5, 33.6, and 31.7 years in 1987, 1992, and 1997, respectively, p < 0.001). New referrals from community cardiologists and family physicians increased more in relative terms than did referrals from the Hospital for Sick Children, Toronto (6.7%, 15%, and 37.5%, p = 0.02). There was a steady increase in patients with previous reparative surgery (48.9%, 59.2%, and 69.2%, p < 0.002). The proportion of patients with previous reoperations also increased (2.3%, 10%, and 9.2%, p < 0.01). Echocardiography remained the predominant method of diagnosis. The diagnostic mix did not change with time. CONCLUSIONS: Over the past 10 years there has been a large increase in adults with congenital heart disease requiring and seeking specialised care in a tertiary health centre, with a concomitant evolution of referral patterns. These data may be helpful in planning of similar paediatric and adult cardiac services for this expanding population.

Adult↗

PubMed1998

Effectiveness of non-mydriatic retinal photography and direct ophthalmoscopy in detecting diabetic retinopathy.

This is a prospective study to compare the effectiveness of non-mydriatic photography with that of direct ophthalmoscopy in screening for diabetic retinopathy in 153 patients attending a hospital clinic in Hong Kong. Retinal photography under physiological mydriasis and direct ophthalmoscopy of patients with dilated pupils were compared with the ophthalmologists' examination results as a reference standard. The prevalence of diabetic retinopathy in this sample population was 15%. The sensitivity of detecting diabetic retinopathy by retinal photography was higher than that of direct ophthalmoscopy (64% versus 41%; 95% confidence interval of difference, 1.2%- 44.3%). Of five patients who had serious retinopathy, retinal photography failed to detect the disease in two; direct ophthalmoscopy failed to detect the disease in all five patients. Specificities of retinal photography and direct ophthalmoscopy were 90% (95% confidence interval, 84%-96%) and 93% (95% confidence interval, 88%-97%), respectively. We conclude that retinal photography is significantly more effective than direct ophthalmoscopy in detecting diabetic retinopathy. In addition, the non-mydriatic camera is easy to use and is the preferred method of screening.

Journal Article↗

PubMed1997

Risk and predictors for pregnancy-related complications in women with heart disease.

BACKGROUND: The physiological changes of pregnancy can result in cardiovascular complications in the mother, which in turn may have fetal implications. Prior studies have focused on specific cardiac lesions or identified univariate predictors. There is a need to refine the risk stratification of women with heart disease so they can receive appropriate obstetrical counseling and care. METHODS AND RESULTS: We examined the outcomes of 221 women with heart disease who underwent 276 pregnancies and received their obstetrical care at three Toronto hospitals from 1986 through 1994. Those who underwent therapeutic abortions were excluded. Among the study participants, there were 24 miscarriages and 252 completed pregnancies (pregnancies not ending in miscarriage). Maternal heart failure, arrhythmia, or stroke occurred in 45 completed pregnancies (18%). There were no maternal deaths. Poor maternal functional class or cyanosis, myocardial dysfunction, left heart obstruction, prior arrhythmia, and prior cardiac events were predictive of maternal cardiac complications. These predictors were incorporated into a point score that can be used to estimate the probability of a cardiac complication in the mother. The rate of cardiac complications for a patient with 0, 1, and >1 of the above factors was 3%, 30%, and 66%, respectively. Neonatal complications occurred in 42 completed pregnancies (17%). Neonatal events included death (2), respiratory distress syndrome (16), intraventricular hemorrhage (2), premature birth (35), and small-for-gestational-age birth weight (14). Poor maternal functional class or cyanosis was predictive of neonatal events. CONCLUSIONS: Despite low maternal and neonatal mortality, pregnancy in women with heart disease is associated with significant cardiac and neonatal morbidity. The probability of maternal cardiac or neonatal events can be predicted from baseline characteristics of the mother.

Adolescent↗

PubMed1997

Sustained ventricular tachycardia in adult patients late after repair of tetralogy of Fallot.

OBJECTIVES: We sought to determine the features associated with sustained monoform ventricular tachycardia (VT) in adult patients late after repair of tetralogy of Fallot (TOF) and to review their management. BACKGROUND: Patients with repair of TOF are at risk for sudden death. Risk factors for ventricular arrhythmia have been identified from patients with ventricular ectopic beats because of the low prevalence of sustained VT. METHODS: From a retrospective chart review of patients assessed between January 1990 and December 1994, 18 adult patients with VT were identified and compared with 192 with repaired TOF free of sustained arrhythmia. RESULTS: There was no significant difference in age at repair, age at follow-up or operative history. Patients with VT had frequent ventricular ectopic beats (6 of 9 vs. 21 of 101), low cardiac index ([mean +/- SD] 2.4 +/- 0.4 vs. 3.0 +/- 0.8) and more structural abnormalities of the right ventricle (outflow tract aneurysms and pulmonary or tricuspid regurgitation) than control patients. Electrophysiologic map-guided operation was performed in 10 of 14 patients who required reoperation. VT has reoccurred in three of these patients. Four patients did not undergo operation (three received amiodarone; one underwent defibrillator implantation). Two patients with VT also had severe heart failure and died. CONCLUSIONS: Most patients with VT late after repair of TOF have outflow tract aneurysms or pulmonary regurgitation, or both. These patients have a greater frequency of ventricular ectopic beats than arrhythmia-free patients after repair of TOF. A combined approach of correcting significant structural abnormalities (pulmonary valve replacement or right ventricular aneurysmectomy, or both) with intraoperative electrophysiologic-guided ablation may reduce the potential risk of deterioration in ventricular function and enable arrhythmia management to be optimized.

Adult↗

PubMed1996

Absence of Q waves after thrombolysis predicts more rapid improvement of regional left ventricular dysfunction.

Although the natural history of regional left ventricular (LV) dysfunction after Q-wave and non-Q-wave myocardial infarction (MI) was well defined in the prethrombolytic era, the functional and structural implications of the absence of Q waves after thrombolysis are less clear. Echocardiography was performed within 48 hours of admission (entry) in 86 patients treated with thrombolysis for their first MI. The extent of abnormal wall motion (AWM; square centimeters) and LV endocardial surface area index (ESA; square centimeters per square meters) were quantified by using a previously validated echocardiographic endocardial surface-mapping technique. Electrocardiography (ECG) performed at 48 hours after thrombolysis was used to classify patients into groups with (Q; n=70) and without (non-Q; n=16) Q waves. All patients in the Q group had regional LV dysfunction on initial echocardiogram compared with 69 percent of those in the non-Q group (p<0.001). When the patients in the non-Q group without AWM were excluded from analysis, there was no significant difference in the extent of AWM between the Q and non-Q groups. Among those patients with AWM on entry, follow-up echocardiography at 6 to 12 weeks demonstrated a significant reduction in extent of AWM for both the Q and non-Q groups. However, the fractional change in AWM was significantly greater in the non-Q than in the Q group (-0.74 +/- 0.28 vs -0.29 +/- 0.44; p<0.02), with a trend toward less AWM at follow-up in the non-Q than in the Q group. The mean ESAi was not significantly different between the two groups at entry or at follow-up. In conclusion, failure to develop Q waves after thrombolysis predicts a lower likelihood of developing regional LV dysfunction and, when such dysfunction is present, predicts a greater degree of recovery.

Aged↗

PubMed1995

Three-dimensional echocardiography improves noninvasive assessment of left ventricular volume and performance.

To calculate left ventricular (LV) volume by two-dimensional echocardiography (2DE), assumptions must be made about ventricular symmetry and geometry. Three-dimensional echocardiography (3DE) can quantitate LV volume without these limitations, yet its incremental value over 2DE is unknown. The purpose of this study was to compare the accuracy of LV volume determination by 3DE to standard 2DE methods. To compare the accuracy of 3DE with standard 2DE algorithms for quantitating LV volume, 28 excised canine ventricles of known volume and varying shapes (15 symmetric and 13 aneurysmal) and 10 instrumented dogs prepared so that instantaneous ventricular volume could be measured were examined by 2DE (bullet and biplane Simpson's formulas) and again by 3DE. In both excised and beating hearts, 3DE was more accurate in quantitating volume than either 2DE method (excised: error = 0.6 +/- 3.2, 2.5 +/- 10.7, and 4.0 +/- 8.5 ml by 3D, bullet, and Simpson's, respectively; beating: error = -0.5 +/- 3.5, -0.3 +/- 9.6, and -7.6 +/- 8.0 ml by 3DE, bullet, and Simpson's, respectively). This difference in accuracy between 3DE and 2DE methods was especially apparent in asymmetric ventricles distorted by ischemia or right ventricular volume overload. Stroke volume and ejection fraction calculated by 3DE also demonstrated better agreement with actual values than the bullet or Simpson methods with less variability (ejection fraction: error = -2.0% +/- 5.1%, 7.7% +/- 8.5%, and 6.8% +/- 12.3% by 3DE, bullet, and Simpson's, respectively). In both in vitro and in vivo settings, 3DE provides improved accuracy for LV volume and performance than current 2DE algorithms.

Animals↗

PubMed1995

Cardiopulmonary function in adult patients late after Fontan repair.

OBJECTIVES: The clinical status and exercise assessment of adult patients late after the Fontan operation were reviewed to determine cardiovascular function. BACKGROUND: The Fontan operation is the final operation for many patients with tricuspid atresia or a single ventricle. Follow-up reports describe most patients to be in Canadian Cardiovascular Society functional class I or II. Objective measures of cardiac performance in the pediatric age group have shown significant dysfunction. METHODS: Forty-seven adult patients were seen late after the Fontan operation at the Toronto Congenital Cardiac Centre for Adults. Thirty of these underwent cycle ergometry to determine maximal exercise capacity. Maximal ventilation, maximal oxygen uptake and anaerobic threshold were determined from a ramp exercise protocol. Ejection fraction at rest and during exercise was measured with gated radionuclide angiography. Results were compared with those of eight normal volunteers. Results are given as mean +/- SD. RESULTS: Thirty patients underwent cardiopulmonary exercise testing 6.7 +/- 3.9 years after a first Fontan operation. Clinically 93% were in functional class I or II. The Fontan group patients had a significantly lower maximal work load (548 +/- 171 vs. 1,094 +/- 190 kilopond-meters, p < 0.00001), anaerobic threshold (11.2 +/- 2.9 vs. 23.6 +/- 4.6 ml/kg per min) and maximal oxygen consumption (14.8 +/- 4.5 vs. 42.1 +/- 10.0 ml/kg per min). Systemic ventricular ejection fraction was lower at rest (38 +/- 12% vs. 58 +/- 7%) and during exercise (40 +/- 15% vs. 70 +/- 8%). CONCLUSIONS: Despite a clinical impression of good function, by objective measures adult patients continue to have significant cardiovascular limitation late after the Fontan operation.

Adult↗

PubMed1994

Three-dimensional reconstruction of ventricular septal defects: validation studies and in vivo feasibility.

OBJECTIVES: The purpose of this study was to demonstrate the feasibility of in vivo three-dimensional reconstruction of ventricular septal defects and to validate its quantitative accuracy for defect localization in excised hearts (used to permit comparison of three-dimensional and direct measurements without cardiac contraction). BACKGROUND: Appreciating the three-dimensional spatial relations of ventricular septal defects could be useful in planning surgical and catheter approaches. Currently, however, echocardiography provides only two-dimensional views, requiring mental integration. A recently developed system automatically combines two-dimensional echocardiographic images with their spatial locations to produce a three-dimensional construct. METHODS: Surgically created ventricular septal defects of varying size and location were imaged and reconstructed, along with the left and right ventricles, in the beating heart of six dogs to demonstrate the in vivo feasibility of producing a coherent image of the defect that portrays its relation to surrounding structures. Two additional gel-filled excised hearts with defects were completely reconstructed. Quantitative localization of the defects relative to other structures (ventricular apexes and valve insertions) was then validated for seven defects in excised hearts. The right septal margins of the exposed defects were also traced and compared with their reconstructed areas and circumferences. RESULTS: The three-dimensional images provided coherent images and correct spatial appreciation of the defects (two inlet, two trabecular, one outlet and one membranous Gerbode in vivo; one inlet and one apical in excised hearts). The distances between defects and other structures in the excised hearts agreed well with direct measures (y = 1.05x-0.18, r = 0.98, SEE = 0.30 cm), as did reconstructed areas (y = 1.0x-0.23, r = 0.98, SEE = 0.21 cm2) and circumferences (y = 0.97x + 0.13, r = 0.97, SEE = 0.3 cm). CONCLUSIONS: Three-dimensional reconstruction of ventricular septal defects can be achieved in the beating heart and provides an accurate appreciation of defect size and location that could be of value in planning interventions.

Animals↗

PubMed1994

Dilated cardiomyopathy.

The etiology and pathogenesis of dilated cardiomyopathy continues to be controversial. The importance of viral and familial etiologies is becoming increasingly recognized. Molecular biology will add significantly to our understanding of these factors in the near future. The differentiation of ischemic from nonischemic dilated cardiomyopathy continues to depend on the use of coronary angiography. Endomyocardial biopsy has a relatively low yield for the detection of specific myocardial disease. To date, there is no specific treatment for dilated cardiomyopathy. Trials evaluating new inodilators have ended in disappointment. The benefits of digoxin, however, appear to be confirmed. Although there has been little progress in the prevention of sudden cardiac death in this population, signal-averaged electrocardiographic analysis shows promise as a tool for risk stratification. At present, the recommended treatment of patients with dilated cardiomyopathy remains identical to that of heart failure in general.

Calcium↗

PubMed1994

Three-dimensional echocardiography. In vivo validation for right ventricular volume and function.

BACKGROUND: Current two-dimensional echocardiographic measures of right ventricular volume are limited by the asymmetrical and crescentic shape of the ventricle and by difficulty in obtaining standardized views. Three-dimensional echocardiographic reconstruction, which does not require geometric assumptions or standardized views, may therefore have potential advantages for determining right ventricular volume. Three-dimensional techniques, however, have not been applied to the right ventricle in vivo, where cardiac motion and contraction could affect accuracy. The purpose of this study was to determine the feasibility and accuracy of three-dimensional echocardiographic reconstruction for quantifying right ventricular volume and function in vivo. In particular, it was designed to test the accuracy of a newly developed system that provides rapid, efficient, and automated three-dimensional data collection (minimizing motion effects) and takes advantage of the full three-dimensional data set to obtain volume. METHODS AND RESULTS: The three-dimensional system was applied to reconstruct the right ventricle and measure its volume and function during 20 hemodynamic stages created in five dogs. Actual instantaneous volumes were measured continuously by an intracavitary balloon connected to an external column. Hemodynamics were varied by volume loading and induction of ischemia. Three-dimensional reconstruction successfully reproduced right ventricular volume compared with actual values at end diastole (y = 1.0 chi-3.4, r = .99, SEE = 1.8 mL) and end systole (y = 1.0 chi+ 2.0, 4 = .98, SEE = 2.5 mL). The mean difference between calculated and actual volumes throughout the cycle was 2.1 mL, or 4.9% of the mean. Ejection fraction also correlated well with actual values (y = 0.96 chi-0.3, r = .98, SEE = 3.3%). CONCLUSIONS: Despite the irregular crescentic shape of the right ventricle, this newly developed three-dimensional system and surfacing algorithm can accurately reconstruct its shape and quantitate its volume and function in vivo without geometric assumptions. The increased efficiency of the system should increase applicability to issues of clinical and research interest.

Algorithms↗

PubMed1993

Comparative efficacy of nifedipine gastrointestinal therapeutic system versus diltiazem when added to beta blockers in stable angina pectoris.

To determine the relative efficacy of nifedipine gastrointestinal therapeutic system (GITS) and diltiazem, 20 patients with angina pectoris and coronary artery disease were studied in a double-blinded, placebo-controlled randomized crossover trial. All patients were taking concomitant beta blockers. Efficacy was assessed by symptoms, exercise treadmill testing, and ambulatory ST-segment monitoring at baseline and after 6 weeks on each medication. Mean daily dose was titrated to 119 +/- 7 mg (nifedipine GITS) and 342 +/- 59 mg (diltiazem). The addition of either nifedipine GITS or diltiazem resulted in a significant reduction in angina frequency, improvement in exercise treadmill duration (7 vs 7 and 8 minutes; baseline vs nifedipine GITS and diltiazem), time to angina onset (4 vs 7 and 7 minutes; baseline vs nifedipine GITS and diltiazem), and time to ST-segment depression (5 vs 6 and 7 minutes; baseline vs nifedipine GITS and diltiazem). There was no significant difference between nifedipine GITS and diltiazem with respect to the magnitude of improvement in anginal symptoms or exercise test parameters. Both nifedipine GITS and diltiazem reduced the overall frequency and duration of ischemic episodes on ambulatory monitoring, but this reduction was not statistically different. Thus, nifedipine GITS and diltiazem at maximally tolerated doses were equally effective at reducing angina and increasing exercise tolerance as beta blockers alone.

Adrenergic beta-Antagonists↗

PubMed1993

Benefit of late coronary reperfusion on ventricular morphology and function after myocardial infarction.

OBJECTIVES: This study was designed to examine the relation between the timing and adequacy of perfusion of the infarct bed and changes in ventricular size and the extent of abnormal wall motion after acute myocardial infarction. METHODS: A validated echocardiographic mapping technique was used to measure the left ventricular endocardial surface area index and the extent of abnormal wall motion over a 3-month period in 91 patients who had either 1) no anterograde or collateral flow to the infarct bed (n = 14), 2) only collateral flow to the infarct bed (n = 18), 3) restoration of anterograde flow to the infarct bed within hours of chest pain (early [n = 43]), or 4) restoration of anterograde flow to the infarct bed within a mean of 5 days after acute myocardial infarction (late [n = 16]). RESULTS: Over the follow-up period, a progressive and significant increase in endocardial surface area index was observed only in the group of patients without anterograde or collateral flow to the infarct bed (entry 64 +/- 3.4 cm2/m2 vs. 3 months 75.9 +/- 6.4 cm2/m2, p < 0.005). In contrast, a progressive reduction in the extent of abnormal wall motion was evident in the group of patients in whom anterograde flow to the infarct bed was restored within hours (entry 26.7 +/- 2.5 cm2 vs. 3 months 11.8 +/- 2.9 cm2, p < 0.001) or days (entry 22.1 +/- 3.6 cm2 vs. 3 months 11.8 +/- 3.3 cm2, p < 0.001) of coronary occlusion. Multiple stepwise linear regression analysis confirmed that by 3 months, 1) ventricular size was independently related to endocardial surface area index and abnormal wall motion at entry (p < 0.0001) and to the change in abnormal wall motion over the follow-up period (p < 0.0001), and 2) the change in abnormal wall motion was related to the presence of anterograde flow to the infarct bed (p < 0.0001) independent of the timing of reperfusion, infarct site or the extent of abnormal wall motion on admission. CONCLUSIONS: After myocardial infarction, the process of ventricular remodeling is influenced by changes in the extent of abnormal wall motion, which in turn are related to the adequacy rather than the timing of perfusion of the infarct bed.

Collateral Circulation↗

PubMed1993

A new integrated system for three-dimensional echocardiographic reconstruction: development and validation for ventricular volume with application in human subjects.

OBJECTIVES: The purpose of this study was to improve three-dimensional echocardiographic reconstruction by developing an automated mechanism for integrating spark gap locating data with corresponding images in real time and to validate use of this mechanism for the measurement of left ventricular volume. BACKGROUND: Initial approaches to three-dimensional echocardiographic reconstruction were often limited by inefficient reconstructive processes requiring manual coordination of two-dimensional images and corresponding spatial locating data. METHODS: In this system, a single computer overlays the binary-encoded positional data on the two-dimensional echocardiographic image, which is then recorded on videotape. The same system allows images to be digitized, traced, analyzed and displayed in three dimensions. This system was validated by using it to reconstruct 11 ventricular phantoms (19 to 271 ml) and 11 gel-filled excised ventricles (21 to 236 ml) imaged in intersecting long- and short-axis views and by apical rotation. To measure cavity volume, a surface was generated by an algorithm that takes advantage of the full three-dimensional data set. RESULTS: Reconstructed cavity volumes agreed well with actual values: y = 0.96x + 2.2 for the ventricular phantoms in long- and short-axis views (r = 0.99, SEE = 2.7 ml); y = 0.95x + 2.9 for the phantoms, reconstructed by apical rotation (r = 0.99, SEE = 2.7 ml); and y = 0.99x + 0.11 ml for the excised ventricles (reconstructed in long- and short-axis views; r = 0.99, SEE = 5.9 ml). The mean difference between three-dimensional and actual volumes was 3% of the mean (3.0 ml) for the phantoms and 6% (4.6 ml) for the excised ventricles. Observer variability was 2.3% for the phantoms and 5.6% for the excised ventricles. Application to 14 normal subjects demonstrated feasibility of left ventricular reconstruction, which provided values for stroke volume that agreed well with an independent Doppler measure (y = 0.97x + 0.94; r = 0.95, SEE = 3.2 ml), with an observer variability of 4.9% (2.4 ml). CONCLUSIONS: A system has therefore been developed that automatically integrates locating and imaging data in no more time than the component two-dimensional echocardiographic scans. This system can accurately reconstruct ventricular volumes in vitro over a wide range and is feasible in vivo, thus laying the foundation for further applications. It has increased the efficiency of three-dimensional reconstruction and enhanced our ability to address clinical and research questions with this technique.

Adult↗

PubMed1993

Three-dimensional echocardiography. In vivo validation for left ventricular volume and function.

BACKGROUND: Current two-dimensional quantitative echocardiographic methods of volume assessment require image acquisition from standardized scanning planes. Left ventricular volume and ejection fraction are then calculated by assuming ventricular symmetry and geometry. These assumptions may not be valid in distorted ventricles. Three-dimensional echocardiography can quantify left ventricular volume without the limitations imposed by the assumptions of two-dimensional methods. We have developed a three-dimensional system that automatically integrates two-dimensional echocardiographic images and their positions in real time and calculates left ventricular volume directly from traced endocardial contours without geometric assumptions. METHODS AND RESULTS: To study the accuracy of this method in quantifying left ventricular volume and performance in vivo, a canine model was developed in which instantaneous left ventricular volume can be measured directly with an intracavitary balloon connected to an external column. Ten dogs were studied at 84 different cavity volumes (4 to 85 cm3) and in conditions of altered left ventricular shape produced by either coronary occlusion or right ventricular volume overload. To demonstrate clinical feasibility, 19 adult human subjects were then studied by this method for quantification of stroke volume. Left ventricular volume, stroke volume, and ejection fraction calculated by three-dimensional echocardiography correlated well with directly measured values (r = .98, .96, .96 for volume, stroke volume, and ejection fraction, respectively) and agreed closely with them (mean difference, -0.78 cm3, -0.60 cm3, -0.32%). In humans, there was a good correlation (r = .94, SEE = 4.29 cm3) and agreement (mean difference, -0.98 +/- 4.2 cm3) between three-dimensional echocardiography and Doppler-derived stroke volumes. CONCLUSIONS: Three-dimensional echocardiography allows accurate assessment of left ventricular volume and systolic function.

Adult↗

PubMed1992

The effect of late patency of the infarct-related coronary artery on left ventricular morphology and regional function after thrombolysis.

The use of early coronary angiography to assess the benefits of coronary patency on left ventricular size and function fails to account for subsequent reocclusion or spontaneous reperfusion. To investigate the relationship between late vessel patency and changes in left ventricular structure and function after thrombolysis, echocardiography was performed within 48 hours and at 6 to 12 weeks in 30 patients treated with intravenous thrombolysis. Left ventricular endocardial surface area index (ESAj; cm2/m2) and extent of abnormal wall motion were quantitated in those with a patent (n = 20) and those with an occluded (n = 10) infarct-related artery on coronary angiography performed 8 +/- 6 days after thrombolysis. Mean ESAi increased from (53 +/- 7 to 61 +/- 10 cm2/m2; p less than 0.02) in the occluded group during the follow-up period but remained unchanged (60 +/- 11 to 62 +/- 11 cm2/m2; p = NS) in the patient group. Mean percentage of abnormal wall motion decreased in the patent group (27 +/- 16% to 18 +/- 16%; p less than 0.01), whereas no significant change was noted in the occluded group (20 +/- 13% to 23 +/- 17%; p = NS). Thus coronary patency at days after thrombolysis is associated with both improvement in regional left ventricular function and attenuated left ventricular dilatation.

Cardiomegaly↗