Craig A. Hamilton

Utility of Fast Cine Magnetic Resonance Imaging and Display for the Detection of Myocardial Ischemia in Patients Not Well Suited for Second Harmonic Stress Echocardiography

BACKGROUND Some patients referred for pharmacological stress testing with transthoracic echocardiography (TTE) are unable to undergo testing owing to poor acoustic windows. Fast cine MRI can be used to assess left ventricular contraction, but its utility for detection of myocardial ischemia in patients poorly suited for echocardiography is unknown. METHODS AND RESULTS One hundred fifty-three patients (86 men and 67 women aged 30 to 88 years) with poor acoustic windows that prevented adequate second harmonic TTE imaging were consecutively referred for MRI to diagnose inducible myocardial ischemia during intravenous dobutamine and atropine. Diagnostic studies were completed in an average of 53 minutes. No patients experienced myocardial infarction, ventricular fibrillation, exacerbation of congestive heart failure, or death. In patients who underwent computer-assisted quantitative coronary angiography, the sensitivity and specificity for detecting a >50% luminal diameter narrowing were 83% and 83%, respectively. In the 103 patients with a negative MRI examination, the cardiovascular occurrence-free survival rate was 97%. CONCLUSIONS Fast cine cardiac MRI provides a mechanism to assess left ventricular contraction and diagnose inducible myocardial ischemia in patients not well suited for stress echocardiography.

Cardiac cycle-dependent changes in aortic area and distensibility are reduced in older patients with isolated diastolic heart failure and correlate with exercise intolerance.

OBJECTIVES The goal of this study was to determine if cardiac cycle-dependent changes in proximal thoracic aortic area and distensibility are associated with exercise intolerance in elderly patients with diastolic heart failure (DHF). BACKGROUND Aortic compliance declines substantially with age. We hypothesized that a reduction in cardiac cycle-dependent changes in thoracic aortic area and distensibility (above that which occurs with aging) could be associated with the exercise intolerance that is prominent in elderly diastolic heart failure patients. METHODS Thirty subjects (20 healthy individuals [10 < 30 years of age and 10 > 60 years of age] and 10 individuals > the age of 60 years with DHF) underwent a magnetic resonance imaging (MRI) study of the heart and proximal thoracic aorta followed within 48 h by maximal exercise ergometry with expired gas analysis. RESULTS The patients with DHF had higher resting brachial pulse and systolic blood pressure, left ventricular mass, aortic wall thickness and mean aortic flow velocity, and, compared with healthy older subjects, they had a significant reduction in MRI-assessed cardiac cycle-dependent change in aortic area and distensibility (p < 0.0001) that correlated with diminished peak exercise oxygen consumption (r = 0.79). After controlling for age and gender in a multivariate analysis, thoracic aortic distensibility was a significant predictor of peak exercise oxygen consumption (p < 0.04). CONCLUSIONS Older patients with isolated DHF have reduced cardiac cycle-dependent changes in proximal thoracic aortic area and distensibility (beyond that which occurs with normal aging), and this correlates with and may contribute to their severe exercise intolerance.

Magnetic Resonance Imaging Determination of Cardiac Prognosis

Background—Regional assessments of left ventricular (LV) wall motion obtained during MRI cardiac stress tests can be used to identify myocardial injury and ischemia, but the utility of MRI stress test results for the assessment of cardiac prognosis is not known. Methods and Results—Two hundred seventy-nine patients referred (because of poor LV endocardial visualization with echocardiography) for dobutamine/atropine MRI for the detection of inducible ischemia were followed for an average of 20 months. After MRI stress testing, the occurrence of myocardial infarction, cardiac death, death attributable to any cause, coronary arterial revascularization, and unstable angina or congestive heart failure requiring hospitalization was determined. In a multivariate analysis, the presence of inducible ischemia (hazard ratio 3.3, CI 1.1 to 9.7) or an LV ejection fraction <40% (hazard ratio 4.2, CI 1.3 to 13.9) was associated with future MI or cardiac death independent of the presence of risk factors for coronary arteriosclerosis. Conclusions—In patients with poor echocardiograms, the results of cardiac MRI stress tests can be used to forecast myocardial infarction or cardiac death.

Low to Moderate Dose Anthracycline-Based Chemotherapy Is Associated With Early Noninvasive Imaging Evidence of Subclinical Cardiovascular Disease

OBJECTIVES The goal of this study was to determine if low to moderate doses of anthracycline-based chemotherapy (Anth-bC) are associated with subclinical cardiovascular (CV) injury. BACKGROUND Cancer survivors who receive Anth-bC experience premature CV events. It is unknown whether low to moderate doses of anthracyclines promote early subclinical CV disease manifested by deteriorations in left ventricular ejection fraction (LVEF) or increases in aortic stiffness, or if these doses are associated with changes in quality of life (QOL). METHODS In 53 men and women with breast cancer, leukemia, or lymphoma, we assessed left ventricular volumes, LVEF, circumferential strain, aortic pulse wave velocity, late gadolinium enhancement, serum B-type natriuretic peptide, troponin I, and the impact of treatment on QOL before and 1, 3, and 6 months after receipt of Anth-bC. RESULTS Participants averaged 50 ± 2 (range 19 to 80) years in age, 58% were women, 17% were black, and they each received a range of 50 to 375 mg/m(2) of doxorubicin-equivalent chemotherapy. Left ventricular end-systolic volume (48 ± 3 ml to 54 ± 3 ml; p = 0.02), left ventricular strain (-17.7 ± 0.4 to -15.1 ± 0.4; p = 0.0003), pulse wave velocity (6.7 ± 0.5 m/s to 10.1 ± 1 m/s; p = 0.0006), and QOL deterioration (15.4 ± 3.3 to 28.5 ± 3.9; p = 0.008) increased, whereas LVEF (58 ± 1% to 53 ± 1%; p = 0.0002) decreased within 6 months after low to moderate doses of Anth-bC. All findings persisted after accounting for age, gender, race (white/black), doxorubicin-equivalent dose, doxorubicin administration technique, comorbidities associated with CV events, and cancer diagnosis (p = 0.02 to 0.0001 for all). There were no new late gadolinium enhancement findings after 6 months. CONCLUSIONS In these study patients, low to moderate doses of Anth-bC were associated with the early development of subclinical abnormalities of cardiac and vascular function that in other populations are associated with the future occurrence of CV events.

Relation of aortic distensibility determined by magnetic resonance imaging in patients ≥60 years of age to systolic heart failure and exercise capacity

Aortic stiffness increases with advancing age and is associated with the age-related decline in exercise capacity in healthy persons. Previous studies have suggested that aortic compliance is reduced in heart failure (HF). Older persons with systolic HF can have particularly severe exercise intolerance. However, the relation between increased aortic stiffness and exercise intolerance in elderly patients with systolic HF has not been examined. Therefore, aortic distensibility of the proximal ascending aorta (assessed by magnetic resonance imaging) and exercise tolerance (assessed by maximal exercise ergometry with expired gas analysis) was measured in 28 subjects (10 healthy subjects aged 20 to 30 years, 10 healthy subjects aged > or =60 years, and 8 subjects aged > or =60 years with systolic HF). Compared with healthy older subjects, patients with systolic HF had markedly decreased distensibility of the proximal aorta (0.5 +/- 0.4 vs 2.2 +/- 1.2 10(-3) mm Hg(-1), p <0.002), decreased peak exercise volume of oxygen consumption (VO2) (858 +/- 248 vs 1,436 +/- 344 ml/min, p <0.001), and increased aortic wall thickness (3.6 +/- 0.7 vs 2.9 +/- 0.4 mm, p <0.04). Aortic distensibility was significantly correlated with peak VO2 (r = 0.80, p <0.0001) and remained so even after being adjusted for age and left ventricular (LV) ejection fraction. These data suggest that decreased aortic distensibility may contribute to exercise intolerance in older patients with HF due to LV systolic dysfunction.

Visualization and Functional Assessment of Proximal and Middle Left Anterior Descending Coronary Stenoses in Humans With Magnetic Resonance Imaging

BACKGROUND Coronary artery bypass grafting improves survival in patients with >70% luminal diameter narrowing of the 3 major epicardial coronary arteries, particularly if there is involvement of the proximal portion of the left anterior descending (LAD) coronary artery. Measurement of coronary flow reserve can be used to identify functionally important luminal narrowing of the LAD artery. Although magnetic resonance imaging (MRI) has been used to visualize coronary arteries and to measure flow reserve noninvasively, the utility of MRI for detecting significant LAD stenoses is unknown. METHODS AND RESULTS Thirty subjects (23 men, 7 women, age 36 to 77 years) underwent MRI visualization of the left main and LAD coronary arteries as well as measurement of flow in the proximal, middle, or distal LAD both at rest and after intravenous adenosine (140 microgram/kg per minute). Immediately thereafter, contrast coronary angiography and when feasible, intracoronary Doppler assessments of coronary flow reserve, were performed. There was a statistically significant correlation between MRI assessments of coronary flow reserve and (a) assessments of coronary arterial stenosis severity by quantitative coronary angiography and (b) invasive measurements of coronary flow reserve (P<0.0001 for both). In comparison to computer-assisted quantitative coronary angiography, the sensitivity and specificity of MRI for identifying a stenosis >70% in the distal left main or proximal/middle LAD arteries was 100% and 83%, respectively. CONCLUSIONS Noninvasive MRI measures of coronary flow reserve correlated well with similar measures obtained with the use of intracoronary Doppler flow wires and predicted significant coronary stenoses (>70%) with a high degree of sensitivity and specificity. MRI-based measurement of coronary flow reserve may prove useful for identification of patients likely to obtain a survival benefit from coronary artery bypass grafting.

Stress Cardiac Magnetic Resonance Imaging With Observation Unit Care Reduces Cost for Patients With Emergent Chest Pain: A Randomized Trial

STUDY OBJECTIVE We determine whether imaging with cardiac magnetic resonance imaging (MRI) in an observation unit would reduce medical costs among patients with emergent non-low-risk chest pain who otherwise would be managed with an inpatient care strategy. METHODS Emergency department patients (n=110) at intermediate or high probability for acute coronary syndrome without electrocardiographic or biomarker evidence of a myocardial infarction provided consent and were randomized to stress cardiac MRI in an observation unit versus standard inpatient care. The primary outcome was direct hospital cost calculated as the sum of hospital and provider costs. Estimated median cost differences (Hodges-Lehmann) and distribution-free 95% confidence intervals (Moses) were used to compare groups. RESULTS There were 110 participants with 53 randomized to cardiac MRI and 57 to inpatient care; 8 of 110 (7%) experienced acute coronary syndrome. In the MRI pathway, 49 of 53 underwent stress cardiac MRI, 11 of 53 were admitted, 1 left against medical advice, 41 were discharged, and 2 had acute coronary syndrome. In the inpatient care pathway, 39 of 57 patients initially received stress testing, 54 of 57 were admitted, 3 left against medical advice, and 6 had acute coronary syndrome. At 30 days, no subjects in either group experienced acute coronary syndrome after discharge. The cardiac MRI group had a reduced median hospitalization cost (Hodges-Lehmann estimate

Aortic Stiffness Increases Upon Receipt of Anthracycline Chemotherapy

588; 95% confidence interval

Assessment of Coronary Arterial Restenosis With Phase-Contrast Magnetic Resonance Imaging Measurements of Coronary Flow Reserve

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Novel Approach to Early Detection of Doxorubicin Cardiotoxicity by Gadolinium-Enhanced Cardiovascular Magnetic Resonance Imaging in an Experimental Model

811); 79% were managed without hospital admission. CONCLUSION Compared with inpatient care, an observation unit strategy involving stress cardiac MRI reduced incident cost without any cases of missed acute coronary syndrome in patients with emergent chest pain.