Biomedical subjects

Michael L Main

Publications and source records attributed to Michael L Main.

9 recordsLinked to original sources

PubMed2006

Contrast administration reduces interobserver variability in determination of left ventricular ejection fraction in patients with left ventricular dysfunction and good baseline endocardial border delineation.

Echocardiographic contrast agents improve endocardial border delineation in patients with technically difficult baseline studies. With medical and device therapy for heart failure increasingly based on left ventricular (LV) ejection fraction (EF) partition values, the accurate and reproducible assessment of LV function is necessary. It was hypothesized that routine contrast enhancement would significantly reduce interobserver variability in the determination of LVEFs in a cohort of patients with LV dysfunction and good baseline endocardial delineation. All patients underwent baseline noncontrast studies followed by contrast-enhanced imaging using Definity. Two experienced echocardiographers, blinded to the clinical data, determined LVEFs using 4 different techniques: noncontrast estimated (NCE), noncontrast calculated (NCC), contrast estimated (CE), and contrast calculated (CC). Using a mixed-model procedure that allows for fixed and random events, the variance due to error and that due to the patient was obtained (interclass correlation). The proportion of variation due to the reader was calculated as 1--interclass correlation. Mean standardized percentage differences ([reader 1 EF--reader 2 EF]/mean EF) were also calculated for each method. The proportion of variation due to the reader was smallest in the CC group and largest in the NCC group (NCE = 0.21, NCC = 0.33, CE = 0.25, CC = 0.11). The results were similar when only patients with NCE EFs >or=20% and or=20% and or=20% and <or=50%.

Cohort Studies↗

PubMed2006

Usefulness of myocardial contrast echocardiography in predicting late mortality in patients with anterior wall acute myocardial infarction.

We investigated whether myocardial contrast echocardiography (MCE) performed soon after acute myocardial infarction (AMI) improves risk stratification for late mortality. MCE after AMI identifies microvascular "no-reflow" and predicts early outcomes; however, the predictive value of MCE for late mortality is unknown. One hundred sixty-seven patients with anterior AMI and left ventricular dysfunction underwent MCE 2 days after admission, and a perfusion score index (PSI) was calculated. Long-term follow-up (mean 39 months) was available for all patients. Patients with normal and abnormal perfusion had similar baseline characteristics. Myocardial contrast echocardiographic PSI was a predictor of mortality as a continuous variable (odds ratio 3.2 for each 1.0 increase in PSI, 95% confidence interval 1.1 to 9.7, p = 0.04). In a logistic regression model, age (odds ratio 2.6 per decade, 95% confidence interval 1.6 to 4.4, p = 0.0002) and PSI (odds ratio 4.5 for each 1.0 increase in PSI, 95% confidence interval 1.3 to 15.4, p = 0.02) were the only significant predictors of mortality. In a subanalysis comparing patients >70 years old with abnormal PSI with all other patients, Kaplan-Meier estimates showed a marked difference in survival over a mean follow-up of 39 months (24% vs 4% mortality, p = 0.0002). In conclusion, MCE refines risk stratification soon after anterior AMI in patients with left ventricular dysfunction. Patients at very high and very low risk of mortality can be identified, and myocardial contrast echocardiographic data are incrementally useful compared with existing clinical and angiographic variables.

Adult↗

PubMed2006

Myocardial contrast echocardiographic estimates of infarct size predict likelihood of left ventricular remodeling after acute anterior wall myocardial infarction.

OBJECTIVES: We sought to determine the utility of myocardial contrast echocardiography (MCE) in predicting left ventricular (LV) remodeling (LVR) in patients with a recent anterior wall myocardial infarction and residual regional LV akinesis. BACKGROUND: Although recent studies have shown that MCE predicts recovery of regional and global LV systolic function after myocardial infarction, the relationship between myocardial perfusion patterns and likelihood of subsequent LVR has not been extensively studied. METHODS: In all, 50 patients (mean age 62 years) underwent contrast-enhanced echocardiography for determination of LV volumes and ejection fraction, and MCE, 2 days after admission, with follow-up contrast-enhanced echocardiography 6 months later. LVR was defined as greater than 15% increase in LV end-diastolic volume index at follow-up. RESULTS: LVR occurred in 19 patients (38%) (group 1), with stable LV volumes in 31 patients (62%) (group 2). Routine clinical and angiographic variables did not differ between groups 1 and 2. Both transmural extent of infarction and number of abnormally perfused myocardial segments (assessed by MCE) predicted LVR. LVR occurred in 55% of patients with transmural perfusion defects, and was less common in those with subendocardial perfusion defects or normal perfusion (31% and 21%, respectively). The mean percent increase in LV size was significantly greater for transmural infarcts (15 +/- 7%) versus subendocardial infarcts or normal perfusion (-1 +/- 8 and 8 +/- 8, respectively). When more than 5 myocardial segments were abnormally perfused, remodeling always occurred and was extensive. CONCLUSIONS: MCE markers of infarct size are useful in predicting subsequent risk of LVR after myocardial infarction. Routine performance of MCE studies in select patients early after infarction may be helpful in further refining risk stratification.

Echocardiography↗

PubMed2006

Pulmonary hemodynamic effects of dipyridamole infusion in patients with normal and elevated pulmonary artery systolic pressure receiving PB127.

BACKGROUND: Intravenous administration of microspheres used as ultrasound contrast agents may potentially alter pulmonary hemodynamics. PB127 (POINT Biomedical Corp., San Carlos, CA) is an investigational ultrasound perfusion-imaging agent used in conjunction with dipyridamole to diagnose coronary artery disease. The effects of PB127 alone or in combination with dipyridamole on pulmonary hemodynamics have not been described. METHODS: We studied 20 patients, including 10 with elevated screening pulmonary artery systolic pressure (>35 mm Hg). Doppler-derived pulmonary hemodynamics were determined before and after continuous infusion of PB127 (0.175 mg/kg diluted in 5% dextrose) or 5% dextrose. Patients then received dipyridamole (0.56 mg/kg) and hemodynamics were again assessed. RESULTS: During PB127/dextrose infusion, there were no significant changes in pulmonary hemodynamics compared with baseline. After dipyridamole, there were small increases in pulmonary artery systolic pressure and in pulmonary flow and a reduction in pulmonary vascular resistance. These changes occurred in patients with normal and elevated pulmonary artery systolic pressure. CONCLUSION: PB127 infusion does not alter pulmonary hemodynamics. Mild alterations of pulmonary hemodynamics occur after dipyridamole administration.

Aged↗

PubMed2006

Transesophageal echocardiographic diagnosis of Aspergillus fumigatus aortitis after percutaneous coronary intervention.

Aspergillus aortitis is an uncommon infection with high mortality and has been reported in patients after cardiopulmonary bypass. We report the first case of Aspergillus aortitis in an immunocompetent man immediately after percutaneous coronary intervention to an aortocoronary bypass graft. In this case, transesophageal echocardiography played a pivotal role in diagnosis.

Aged↗

PubMed2004

Usefulness of myocardial contrast echocardiography in predicting global left ventricular functional recovery after anterior wall acute myocardial infarction.

Although multiple recent studies have shown that myocardial contrast echocardiography (MCE) reliably differentiates between regional stunning and necrosis after acute myocardial infarction (AMI), prognosis is more closely related to measures of global left ventricular systolic function. One hundred fifteen patients underwent baseline wall motion assessment and MCE 2 days after admission and follow-up echocardiography a mean of 69 days later. Good agreement was found between perfusion score index and follow-up wall motion score index, indicating that MCE performed early after anterior wall AMI may be clinically useful in routine post-AMI risk stratification.

Aged↗

PubMed2004

Reperfusion assessment using myocardial contrast echocardiography in patients with ST-segment elevation acute myocardial infarction.

In this study, 29 patients underwent myocardial contrast echocardiography after presentation with ST-segment elevation acute myocardial infarction but before coronary angiography using a continuous infusion of microbubbles and real-time imaging with a low mechanical index. Patients with transmural perfusion defects at presentation subsequently had much larger infarctions (as measured by peak creatine phosphokinase-MB fraction) than did those with normal perfusion, indicating that myocardial contrast echocardiography may be a useful means to determine adequacy of reperfusion after thrombolytic therapy and in the selection of patients for adjunctive treatment, such as "rescue angioplasty."

Contrast Media↗

PubMed2003

Real-time assessment of myocardial perfusion during balloon angioplasty of the left anterior descending coronary artery.

Balloon occlusion and release during elective percutaneous coronary intervention (PCI) provides a unique opportunity to study dynamic temporal alterations in myocardial perfusion in a controlled setting. These changes in flow and volume mimic those that occur during presentation with, and successful therapy of, ST-segment elevation acute myocardial infarction (AMI). Eleven patients underwent myocardial contrast echocardiography (MCE) using a continuous infusion of Definity at baseline, during coronary occlusion, and during reactive hyperemia immediately after balloon deflation. Fifty separate flow state sequences were acquired, and off-line analysis was performed to determine myocardial contrast intensity within a region of interest in the distribution of the left anterior descending artery (LAD). A reader blinded to flow state also performed qualitative evaluation (perfusion or lack of perfusion). Quantitative analysis demonstrated significant differences in myocardial contrast intensity by flow state (p = 0.0001 for occlusion vs reperfusion). Qualitative assessment demonstrated a high rate of correct classification (92%). Real-time myocardial perfusion assessment using MCE accurately differentiates coronary occlusion and reactive hyperemia in humans by qualitative and quantitative assessment. This technique may be clinically useful in assessing the efficacy of thrombolytic therapy in ST-segment elevation AMI and in clinical trial assessment of new drugs and devices aimed at limitation of infarct size.

Aged↗

PubMed2002

Combined assessment of microvascular integrity and contractile reserve improves differentiation of stunning and necrosis after acute anterior wall myocardial infarction.

OBJECTIVES: We sought to determine the relative accuracy of myocardial contrast echocardiography (MCE) and low-dose dobutamine echocardiography (LDDE) in predicting recovery of left ventricular (LV) function in patients with a recent anterior wall myocardial infarction (MI). BACKGROUND: Left ventricular dysfunction after acute MI may be secondary to myocardial stunning or necrosis. Myocardial contrast echocardiography allows real-time echocardiographic perfusion assessment from a venous injection of a fluorocarbon-based contrast agent. Although this technique is promising, it has not been compared with LDDE. METHODS: Forty-six patients underwent baseline wall motion assessment, MCE, and LDDE two days after admission, as well as follow-up echocardiography after a mean period of 53 days. RESULTS: Perfusion by MCE predicted recovery of segmental function with a sensitivity of 69%, specificity of 85%, positive predictive value of 74%, negative predictive value of 81%, and overall accuracy of 78%. Contractile reserve by LDDE predicted recovery of segmental function with a sensitivity of 50%, specificity of 88%, positive predictive value of 72%, negative predictive value of 73%, and overall accuracy of 73%. Concordant test results occurred in 74% of segments and further increased the overall accuracy to 85%. The mean wall motion score at follow-up was significantly better in perfused versus nonperfused segments (1.9 vs. 2.6, p < 0.0001) and in segments with contractile reserve, compared with segments lacking contractile reserve (1.9 vs. 2.5, p < 0.0001). CONCLUSION: Myocardial contrast echocardiography compares favorably with LDDE in predicting recovery of regional LV dysfunction after acute anterior wall MI. Concordant contractile reserve and myocardial perfusion results further enhance the diagnostic accuracy.

Aged↗