Coronary risk factors and myocardial perfusion in asymptomatic adults: the Multi-Ethnic Study of Atherosclerosis (MESA)

Myocardial perfusion defects and coronary risk factors in symptomatic and asymptomatic elderly women

BACKGROUND

We investigated the relation between risk factors of coronary artery disease (CAD) and myocardial ischemia detected by (201)Tl SPECT in elderly women.

METHODS

306 women aged >or=75 yr (79.1 +/- 3.6 yr) who underwent pharmacologic (201)Tl SPECT for suspected CAD based on symptoms or CAD risk factors were included. Coronary risk factors were evaluated by medical records, and included diabetes mellitus (DM), hypertension, hypercholesterolemia, cigarette smoking, greater age (>or=80 yr), and obesity. Summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) were calculated based on stress and redistribution SPECT images for semi-quantification.

RESULTS

The symptomatic group (n = 110) had a 34.5% perfusion defect rate. The asymptomatic group (n = 196) had a significantly lower perfusion defect rate of 16.8%. However, this significantly increased to 29.4% and 22.0% in the presence of diabetes mellitus (DM) and hypertension, respectively. In addition, the summed stress score of asymptomatic patients (12.4 +/- 6.0) was not lower but comparable to that of symptomatic patients (10.0 +/- 6.0).

CONCLUSIONS

In elderly women suspected of CAD, pharmacologic perfusion imaging can be used to identify myocardial ischemia in patients with angina as well as asymptomatic subjects with concurrent DM or hypertension.

Fully automated registration of first-pass myocardial perfusion MRI using independent component analysis

This paper presents a novel method for registration of cardiac perfusion MRI. The presented method successfully corrects for breathing motion without any manual interaction using Independent Component Analysis to extract physiologically relevant features together with their time-intensity behavior. A time-varying reference image mimicking intensity changes in the data of interest is computed based on the results of ICA, and used to compute the displacement caused by breathing for each frame. Qualitative and quantitative validation of the method is carried out using 46 clinical quality, short-axis, perfusion MR datasets comprising 100 images each. Validation experiments showed a reduction of the average LV motion from 1.26+/-0.87 to 0.64+/-0.46 pixels. Time-intensity curves are also improved after registration with an average error reduced from 2.65+/-7.89% to 0.87+/-3.88% between registered data and manual gold standard. We conclude that this fully automatic ICA-based method shows an excellent accuracy, robustness and computation speed, adequate for use in a clinical environment.

Evaluation of cardiac magnetic resonance imaging parameters to detect anatomically and hemodynamically significant coronary artery disease

BACKGROUND

Cardiac magnetic resonance (cMR) perfusion imaging is a promising technique to assess coronary artery disease (CAD). Our objective was to evaluate accuracy of various cMR imaging parameters to detect significant CAD as compared with angiography or fractional flow reserve (FFR).

METHODS

We prospectively enrolled 37 patients who underwent coronary angiography, FFR, and cMR perfusion imaging. Semiquantitative assessments, namely maximum up-slope and peak-intensity indexes, were derived from time-intensity ratios between rest and stress. Myocardial perfusion reserve (MPR), calculated using Fermi deconvolution technique, was the quantitative cMR imaging parameter. Qualitative assessments were visually performed by independent analysts. Accuracy of quantitative, semiquantitative, and qualitative cMR imaging data was compared with quantitative coronary angiography in 108 segments and FFR in 44 segments.

RESULTS

Sensitivity and specificity for hemodynamically significant CAD (FFR < or = 0.75) were 92.9% and 56.7%, respectively, for MPR (cutoff, 2.06). Area under the curve to detect FFR < or = 0.75 was 0.78 for MPR (P < .01), 0.63 for up-slope (P = NS), and 0.66 (P = NS) for peak intensity. Sensitivity and specificity for anatomically significant CAD (> 50% diameter stenosis [DS]) were 87.2% and 49.2%, respectively, for MPR (cutoff, 2.06). Area under the curve was 0.75 for MPR, 0.69 for up-slope, and 0.65 for peak intensity to detect > 50% DS (all P < .05). Visual assessment yielded sensitivity of 78.6% and specificity of 65.5% to predict FFR < or = 0.75 and sensitivity of 74.5% and specificity of 67.2% to predict > 50% DS.

CONCLUSIONS

Myocardial perfusion reserve appears to be the most accurate index to detect anatomical and hemodynamically significant CAD. Standardization of such quantitative methods, with minimal operator dependency, would be useful for clinical and research applications.

Quantitative magnetic resonance perfusion imaging detects anatomic and physiologic coronary artery disease as measured by coronary angiography and fractional flow reserve

OBJECTIVES

To evaluate the ability of quantitative perfusion cardiac magnetic resonance (CMR) to assess the hemodynamic significance of coronary artery disease (CAD) compared with well-established anatomic and physiologic techniques.

BACKGROUND

Fractional flow reserve (FFR) is considered by many investigators to be a reliable stenosis-specific method to determine hemodynamically significant CAD. Quantitative perfusion CMR is a promising noninvasive approach to detect CAD but has yet to be validated against FFR.

METHODS

This is a prospective study in patients with suspected CAD who underwent coronary angiography, FFR, and CMR assessments. The quantitative myocardial perfusion reserve (MPR) was calculated in 720 myocardial sectors (8 sectors/slice). The MPR was calculated from the ratio between stress and rest myocardial flow based on signal intensity time curves using deconvolution analysis. Stress was simulated with adenosine for both FFR and MPR. The MPR assessments were compared to FFR (n = 44 coronary segments) and quantitative coronary angiography (n = 108 segments) in the corresponding coronary territories.

RESULTS

The MPR was 1.54 +/- 0.36 in segments with FFR < or =0.75 (n = 14) and 2.11 +/- 0.68 in those with FFR >0.75 (n = 30; p = 0.0054). An MPR cutoff of 2.04 was 92.9% (95% CI 77.9 to 100.0) sensitive and 56.7% (95% CI 32.8 to 80.6) specific in predicting a coronary segment with FFR < or =0.75. The MPR was 1.54 +/- 0.49 in coronary segments with > or =50% diameter stenosis (DS) (n = 47) and 2.13 +/- 0.80 in segments with <50% DS (n = 61; p < 0.001). An MPR cutoff of 2.04 was 85.1% (95% CI 71.1 to 99.2) sensitive and 49.2% (95% CI 33.6 to 64.8) specific in predicting CAD with > or =50% DS.

CONCLUSIONS

Quantitative perfusion CMR is a safe noninvasive test that represents a stenosis-specific alternative to determine the hemodynamic significance of CAD.

Beneficial effects of eplerenone versus hydrochlorothiazide on coronary circulatory function in patients with diabetes mellitus

CONTEXT

Impaired coronary circulatory function predicts cardiovascular events, the leading cause of death in patients with diabetes mellitus. Aldosterone causes cardiovascular injury and is not suppressed by chronic angiotensin converting enzyme (ACE) inhibitor therapy.

OBJECTIVE

Our objective was to assess whether mineralocorticoid receptor activation contributes to coronary circulatory dysfunction in patients with diabetes who are already receiving ACE inhibitor therapy.

DESIGN AND SETTING

A randomized, double-blind, crossover study with an intervening washout period of at least 4 wk was conducted with ambulatory patients from the community.

PATIENTS

Patients included 16 subjects (11 men, eight Caucasians; mean age, 53 yr; mean body mass index, 38.0 kg/m2) with diabetes and albuminuria but without clinical cardiovascular disease.

INTERVENTIONS

ACE inhibitors were switched to enalapril 20 mg daily, and other antihypertensives were discontinued. Amlodipine 5-10 mg daily was added to achieve blood pressures less than 130/80 mm Hg. Subjects then received, in random order, 6 wk of the mineralocorticoid receptor antagonist eplerenone 50 mg (with placebo pill) daily and 6 wk of another diuretic, hydrochlorothiazide 12.5 mg (with potassium 10 mEq) daily.

MAIN OUTCOME MEASURES

Before and after each 6-wk treatment period, we measured coronary circulatory function (adenosine-stimulated myocardial perfusion reserve) and endothelial function (brachial artery reactivity and peripheral arterial tonometry).

RESULTS

The eplerenone and hydrochlorothiazide groups had similar blood pressures, serum potassium, glycemia, and endothelial function. Although pretreatment myocardial perfusion reserve did not differ between groups, myocardial perfusion reserve was significantly higher after eplerenone than after hydrochlorothiazide (median 1.57 vs. 1.30; P = 0.03).

CONCLUSIONS

Mineralocorticoid receptor blockade improves coronary circulatory function compared with hydrochlorothiazide in patients with diabetes already receiving ACE inhibitor therapy.

Cardiovascular magnetic resonance perfusion imaging at 3-tesla for the detection of coronary artery disease: a comparison with 1.5-tesla

OBJECTIVES

This study was designed to establish the diagnostic accuracy of cardiovascular magnetic resonance (CMR) perfusion imaging at 3-Tesla (T) in suspected coronary artery disease (CAD).

BACKGROUND

Myocardial perfusion imaging is considered one of the most compelling applications for CMR at 3-T. The 3-T systems provide increased signal-to-noise ratio and contrast enhancement (compared with 1.5-T), which can potentially improve spatial resolution and image quality.

METHODS

Sixty-one patients (age 64 +/- 8 years) referred for elective diagnostic coronary angiography (CA) for investigation of exertional chest pain were studied (before angiogram) with first-pass perfusion CMR at both 1.5- and 3-T and at stress (140 microg/kg/min intravenous adenosine, Adenoscan, Sanofi-Synthelabo, Guildford, United Kingdom) and rest. Four short-axis images were acquired during every heartbeat using a saturation recovery fast-gradient echo sequence and 0.04 mmol/kg Gd-DTPA bolus injection. Quantitative CA served as the reference standard. Perfusion deficits were interpreted visually by 2 blinded observers. We defined CAD angiographically as the presence of > or =1 stenosis of > or =50% diameter in any of the main epicardial coronary arteries or their branches with a diameter of > or =2 mm.

RESULTS

The prevalence of CAD was 66%. All perfusion images were found to be visually interpretable for diagnosis. We found that 3-T CMR perfusion imaging provided a higher diagnostic accuracy (90% vs. 82%), sensitivity (98% vs. 90%), specificity (76% vs. 67%), positive predictive value (89% vs. 84%), and negative predictive value (94% vs. 78%) for detection of significant coronary stenoses compared with 1.5-T. The diagnostic performance of 3-T perfusion imaging was significantly greater than that of 1.5-T in identifying both single-vessel disease (area under receiver-operator characteristic [ROC] curve: 0.89 +/- 0.05 vs. 0.70 +/- 0.08; p < 0.05) and multivessel disease (area under ROC curve: 0.95 +/- 0.03 vs. 0.82 +/- 0.06; p < 0.05). There was no difference between field strengths for the overall detection of coronary disease (area under ROC curve: 0.87 +/- 0.05 vs. 0.78 +/- 0.06; p = 0.23).

CONCLUSIONS

Our study showed that 3-T CMR perfusion imaging is superior to 1.5-T for prediction of significant single- and multi-vessel coronary disease, and 3-T may become the preferred CMR field strength for myocardial perfusion assessment in clinical practice.

Evidence for microvascular dysfunction in hypertrophic cardiomyopathy: new insights from multiparametric magnetic resonance imaging

BACKGROUND

Microvascular dysfunction in hypertrophic cardiomyopathy (HCM) may create an ischemic substrate conducive to sudden death, but it remains unknown whether the extent of hypertrophy is associated with proportionally poorer perfusion reserve. Comparisons between magnitude of hypertrophy, impairment of perfusion reserve, and extent of fibrosis may offer new insights for future clinical risk stratification in HCM but require multiparametric imaging with high spatial and temporal resolution.

METHODS AND RESULTS

Degree of hypertrophy, myocardial blood flow at rest and during hyperemia (hMBF), and myocardial fibrosis were assessed with magnetic resonance imaging in 35 HCM patients (9 [26%] male/26 female) and 14 healthy controls (4 [29%] male/10 female), aged 18 to 78 years (mean+/-SD, 42+/-14 years) with the use of the American Heart Association left ventricular 16-segment model. Resting MBF was similar in HCM patients and controls. hMBF was lower in HCM patients (1.84+/-0.89 mL/min per gram) than in healthy controls (3.42+/-1.76 mL/min per gram, with a difference of -0.95+/-0.30 [SE] mL/min per gram; P<0.001) after adjustment for multiple variables, including end-diastolic segmental wall thickness (P<0.001). In HCM patients, hMBF decreased with increasing end-diastolic wall thickness (P<0.005) and preferentially in the endocardial layer. The frequency of endocardial hMBF falling below epicardial hMBF rose with wall thickness (P=0.045), as did the incidence of fibrosis (P<0.001).

CONCLUSIONS

In HCM the vasodilator response is reduced, particularly in the endocardium, and in proportion to the magnitude of hypertrophy. Microvascular dysfunction and subsequent ischemia may be important components of the risk attributable to HCM.

Detection of cardiac small vessel disease by adenosine-stress magnetic resonance

BACKGROUND

Patients testing positive for myocardial ischemia but without significant coronary artery (CA) stenosis in coronary angiography (CXA) are characterized as having "small vessel disease" (SVD). The aim of our study was to identify these patients by stress perfusion cardiac magnetic resonance (CMR).

METHODS

317 patients with suspected myocardial ischemia and clinical indication for CXA were scanned < 72 h before CXA in a whole-body 1.5T scanner. After 3 min of adenosine infusion (140 microg/kg/min), a myocardial first-pass perfusion sequence in 4-5 contiguous short-axis orientations using a Gadolinium-based contrast agent (0.1 mmol/kg) was performed. Images were analyzed qualitatively by two independent and blinded investigators.

RESULTS

Perfusion deficits were detected in 93% of our patients. In 78% of patients with relevant perfusion delay, perfusion deficits extended to > 1/3 of the wall thickness in > or = 2 myocardial segments, persisted for > 5 heartbeats and were regarded as relevant coronary macroangiopathy. All of these patients had significant CA stenosis (60% had luminal narrowing > 70% and 18% had 50-70%). 22% of the patients had perfusion deficits affecting < or = 1/3 of wall thickness with persistence for < or = 5 heartbeats and were regarded as having SVD. None of these patients had a CA stenosis of > 50% or received CA revascularization. These patients more frequently had hypertension (p<0.0001), diabetes (p<0.05) and circumferential perfusion deficits (p<0.0001) than other patients.

CONCLUSION

Stress perfusion CMR allows non-invasive differentiation between patients with significant CA stenosis and patients with SVD caused by hypertension and/or diabetes based on the temporal and spatial extent of perfusion deficits. Patients with SVD more often have diffuse perfusion deficits with shorter persistence than patients with significant CA disease.

Lower myocardial perfusion reserve is associated with decreased regional left ventricular function in asymptomatic participants of the multi-ethnic study of atherosclerosis

BACKGROUND

Myocardial ischemia is an important determinant of regional left ventricular systolic function. Myocardial blood flow reserve may be impaired by cardiovascular disease before alterations of myocardial perfusion at rest become manifest. Nevertheless, the relation between flow reserve and regional myocardial function has not been studied in individuals without a history of clinical heart disease.

METHODS AND RESULTS

Seventy-four participants (66+/-9 years, mean+/-SD) of the Multi-Ethnic Study of Atherosclerosis (MESA) underwent myocardial magnetic resonance tagging and contrast-enhanced perfusion studies. Regional myocardial function was evaluated as peak systolic circumferential strain (Ecc) in the three main coronary territories (left anterior descending [LAD], left circumflex, and right coronary artery [RCA]). Myocardial blood flow at rest and during adenosine-induced hyperemia was quantified by contrast-enhanced magnetic resonance imaging, to study the relation between regional flow and function after multivariable adjustment for age, gender, body mass index, left ventricular mass, and traditional risk factors. Lower regional myocardial blood flow during hyperemia was associated with reduced regional left ventricular function expressed as lower Ecc in the RCA (P<0.01) and left circumflex regions (P<0.05) measured in the subendocardium, mid-wall, and subepicardium. In contrast, no significant association was seen in the LAD territory (P=0.16). In addition, segmental function in LAD and RCA regions was reduced when individuals in the lowest 10th percentile for regional myocardial flow reserve were compared with the other participants. Absolute decreases in mid-wall Ecc LAD and RCA and global Ecc were 3.0%, 3.4%, and 2.8%, respectively (P<0.05 for all regions).

CONCLUSIONS

Lower myocardial flow reserve is related to reduced regional function in asymptomatic individuals.