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

Obesity and statins are both independent predictors of enhanced coronary arteriolar dilation in patients undergoing heart surgery

Background

A paradoxical inverse relationship between body mass index, morbidity and mortality in patients with ischemic heart disease has been noted; but the underlying mechanisms remain unclear. Given that coronary resistance arteries are the primary regulators of myocardial blood flow, we examined the effects of obesity and medication on dilator function in coronary microvessels.

Methods

Bradykinin-induced coronary dilation was assessed by videomicroscopy in ex vivo coronary arterioles obtained from 64 consecutive patients undergoing heart surgery. Multi-variable linear regression and logistic regression were used to investigate the effects of obesity (BMI ≥ 30 kg/M²) and the influences of medications on vessel responses.

Results

In isolated, pressurized (80 mmHg) coronary arterioles of obese and non-obese patient the active (73±4 vs. 79±13 μm) and passive (111 ± 5.5 vs. 118 ± 5.0 μm) diameters were similar. Bradykinin elicited substantial dilation in coronary arterioles, with a similar magnitude in obese and non-obese patients (to 10^-8 M: 55 ± 5% vs. 46 ± 5%, P = 0.20), but with significantly enhanced sensitivity in obesity (EC50: 8.2x10^-9 M vs. 1.9x10^-8 M, respectively, P = 0.03). When adjusted for other risk factors and medications, obesity and statins were determined to be the only positive predictors of enhanced dilation, as assessed with multiple regression analysis. Moreover, obese patients with or without statin exhibited significantly increased coronary dilation to bradykinin, when compared to non-obese patients without statin therapy.

Conclusions

Obesity and statin therapy are independently associated with an enhanced dilator function of coronary arterioles in patients undergoing heart surgery, which may offer a potential mechanism for the better cardiovascular outcome described earlier as the obesity paradox.

MR myocardial perfusion imaging

Contrast material-enhanced myocardial perfusion imaging by using cardiac magnetic resonance (MR) imaging has, during the past decade, evolved into an accurate technique for diagnosing coronary artery disease, with excellent prognostic value. Advantages such as high spatial resolution; absence of ionizing radiation; and the ease of routine integration with an assessment of viability, wall motion, and cardiac anatomy are readily recognized. The need for training and technical expertise and the regulatory hurdles, which might prevent vendors from marketing cardiac MR perfusion imaging, may have hampered its progress. The current review considers both the technical developments and the clinical experience with cardiac MR perfusion imaging, which hopefully demonstrates that it has long passed the stage of a research technique. In fact, cardiac MR perfusion imaging is moving beyond traditional indications such as diagnosis of coronary disease to novel applications such as in congenital heart disease, where the imperatives of avoidance of ionizing radiation and achievement of high spatial resolution are of high priority. More wide use of cardiac MR perfusion imaging, and novel applications thereof, are aided by the progress in parallel imaging, high-field-strength cardiac MR imaging, and other technical advances discussed in this review.

Impaired coronary microvascular function and its association with disease duration and inflammation in patients with psoriasis

SUBJECTS

Thirty-six patients with psoriasis and 56 healthy volunteers were included in this study.

METHODS

Echocardiographic examination included transmitral peak flow velocities of the early phase (E) and late phase (A) of the mitral inflow, left ventricular myocardial velocity measurements, and coronary flow reserve (CFR) measurement.

RESULTS

Baseline coronary diastolic peak flow velocity (DPFV) of left anterior descending artery (LAD) was significantly higher in the psoriasis group. However, hyperemic DPFV was slightly lower and CFR (2.19 ± 0.39 vs. 2.60 ± 0.31, P < 0.0001) was significantly lower in the psoriasis group than in the control group. CFR was significantly and inversely correlated with disease duration, Psoriasis Area and Severity Index (PASI) score, and hsCRP.

CONCLUSION

CFR is decreased in patients with psoriasis, and it correlates to disease duration, PASI score, and inflammation.

The association of systemic microvascular changes with lung function and lung density: a cross-sectional study

Smoking causes endothelial dysfunction and systemic microvascular disease with resultant end-organ damage in the kidneys, eyes and heart. Little is known about microvascular changes in smoking-related lung disease. We tested if microvascular changes in the retina, kidneys and heart were associated with obstructive spirometry and low lung density on computed tomography. The Multi-Ethnic Study of Atherosclerosis recruited participants age 45-84 years without clinical cardiovascular disease. Measures of microvascular function included retinal arteriolar and venular caliber, urine albumin-to-creatinine ratio and, in a subset, myocardial blood flow on magnetic resonance imaging. Spirometry was measured following ATS/ERS guidelines. Low attenuation areas (LAA) were measured on lung fields of cardiac computed tomograms. Regression models adjusted for pulmonary and cardiac risk factors, medications and body size. Among 3,397 participants, retinal venular caliber was inversely associated with forced expiratory volume in one second (FEV(1)) (P<0.001) and FEV(1)/forced vital capacity (FVC) ratio (P = 0.04). Albumin-to-creatinine ratio was inversely associated with FEV(1) (P = 0.002) but not FEV(1)/FVC. Myocardial blood flow (n = 126) was associated with lower FEV(1) (P = 0.02), lower FEV(1)/FVC (P = 0.001) and greater percentage LAA (P = 0.04). Associations were of greater magnitude among smokers. Low lung function was associated with microvascular changes in the retina, kidneys and heart, and low lung density was associated with impaired myocardial microvascular perfusion. These cross-sectional results suggest that microvascular damage with end-organ dysfunction in all circulations may pertain to the lung, that lung dysfunction may contribute to systemic microvascular disease, or that there may be a shared predisposition.

Left ventricular mass in patients with a cardiomyopathy after treatment with anthracyclines

We aimed to describe the cardiac magnetic resonance (CMR) findings and determine the prognostic variables in patients with a cardiomyopathy after treatment with anthracyclines. CMR imaging was performed in 91 patients (58% men, mean age 43 ± 18 years, and mean anthracycline dose of 276 ± 82 mg/m(2)) with a reduced ejection fraction after anthracycline-based chemotherapy. Major adverse cardiovascular events were defined as cardiovascular death, appropriate implantable cardioverter-defibrillator therapy, and admission for decompensated heart failure. Patients presented a median of 88 months (interquartile range 37 to 138) after chemotherapy and were followed for 27 months (interquartile range 22 to 38). Late gadolinium enhancement was an uncommon finding (5 patients, 6%) despite a reduced ejection fraction (36 ± 8%). An inverse association was found between the anthracycline dose and the indexed left ventricular (LV) mass by CMR (r = -0.67, p <0.001). A total of 52 adverse cardiac events occurred (event rate of 22%/year). When the patients were grouped according to the presence or absence of a major adverse cardiovascular event, the indexed LV mass and glomerular filtration rate were lower and the anthracycline dose was greater among the patients who experienced an adverse event. In a multivariate model, the indexed LV mass demonstrated the strongest association with major adverse cardiovascular events (hazard ratio 0.89, chi-square 26, p <0.001). In conclusion, myocardial scar by late gadolinium enhancement-CMR is infrequent in patients with anthracycline-cardiomyopathy despite a reduced ejection fraction, the event rate in patients with established anthracycline-cardiotoxicity is high, and indexed LV mass by CMR imaging is a predictor of adverse cardiovascular events.

Microvascular responsiveness in obesity: implications for therapeutic intervention

Obesity has detrimental effects on the microcirculation. Functional changes in microvascular responsiveness may increase the risk of developing cardiovascular complications in obese patients. Emerging evidence indicates that selective therapeutic targeting of the microvessels may prevent life-threatening obesity-related vascular complications, such as ischaemic heart disease, heart failure and hypertension. It is also plausible that alterations in adipose tissue microcirculation contribute to the development of obesity. Therefore, targeting adipose tissue arterioles could represent a novel approach to reducing obesity. This review aims to examine recent studies that have been focused on vasomotor dysfunction of resistance arteries in obese humans and animal models of obesity. Particularly, findings in coronary resistance arteries are contrasted to those obtained in other vascular beds. We provide examples of therapeutic attempts, such as use of statins, ACE inhibitors and insulin sensitizers to prevent obesity-related microvascular complications. We further identify some of the important challenges and opportunities going forward.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Systolic versus diastolic acquisition in myocardial perfusion MR imaging

PURPOSE

To compare myocardial blood flow (MBF) at systole and diastole and determine the diagnostic accuracy of both phases in patients suspected of having coronary artery disease (CAD).

MATERIALS AND METHODS

The study was approved by the regional ethics committee, and all patients gave written informed consent. After coronary angiography, 40 patients (27 men; mean age, 64 years ± 8) underwent stress-rest perfusion magnetic resonance (MR) imaging at 1.5 T, with images aquired simultaneously at end systole and middiastole. Patients were classified as having CAD (stenosis .70%) or no significant CAD. In patients with CAD, myocardial segments were classified as stenosis-dependent (downstream of significant stenosis) or remote. MBF and myocardial perfusion reserve (MPR) were calculated for each segment, and mean values in each phase were compared with paired t tests. The diagnostic accuracy of each phase was determined with receiver operating characteristic (ROC) analysis.

RESULTS

Twenty-one of the 40 patients (53%) had CAD. Resting MBF was similar in both phases for patients with and patients without CAD (P > .05). Stress MBF was greater in diastole than systole in normal, remote, and stenosis-dependent segments (3.75 mL/g/min ± 1.50 vs 3.15 mL/g/min ± 1.10, respectively, for normal segments; 2.75 mL/g/min ± 1.20 vs 2.38 mL/g/min ± 0.99, respectively, for remote segments; 2.49 mL/g/min ± 1.07 vs 2.23 mL/g/min ± 0.90, respectively, for stenosis-dependent segments; P <.01). MPR was greater in diastole than systole in all segment groups (P < .05). The diagnostic accuracies at diastole and systole were similar (area under the ROC curve = 0.79 and 0.82, respectively; P = .30).

CONCLUSION

Myocardial perfusion MR estimates of stress MBF and MPR were greater in diastole than systole in patients with and patients without CAD. However, both phases had similar diagnostic accuracy. These observations may be relevant to other dynamic perfusion methods, including computed tomography and echocardiography.

Microvascular dysfunction: a potential mechanism in the pathogenesis of obesity-associated insulin resistance and hypertension

The intertwined epidemics of obesity and related disorders such as hypertension, insulin resistance, type 2 diabetes, and subsequent cardiovascular disease pose a major public health challenge. To meet this challenge, we must understand the interplay between adipose tissue and the vasculature. Microvascular dysfunction is important not only in the development of obesity-related target-organ damage but also in the development of cardiovascular risk factors such as hypertension and insulin resistance. The present review examines the role of microvascular dysfunction as an explanation for the associations among obesity, hypertension, and impaired insulin-mediated glucose disposal. We also discuss communicative pathways from adipose tissue to the microcirculation.

Pericardial fat and myocardial perfusion in asymptomatic adults from the Multi-Ethnic Study of Atherosclerosis

Background

Pericardial fat has adverse effects on the surrounding vasculature. Previous studies suggest that pericardial fat may contribute to myocardial ischemia in symptomatic individuals. However, it is unknown if pericardial fat has similar effects in asymptomatic individuals.

Methods

We determined the association between pericardial fat and myocardial blood flow (MBF) in 214 adults with no prior history of cardiovascular disease from the Minnesota field center of the Multi-Ethnic Study of Atherosclerosis (43% female, 56% Caucasian, 44% Hispanic). Pericardial fat volume was measured by computed tomography. MBF was measured by MRI at rest and during adenosine-induced hyperemia. Myocardial perfusion reserve (PR) was calculated as the ratio of hyperemic to resting MBF.

Results

Gender-stratified analyses revealed significant differences between men and women including less pericardial fat (71.9±31.3 vs. 105.2±57.5 cm³, p<0.0001) and higher resting MBF (1.12±0.23 vs. 0.93±0.19 ml/min/g, p<0.0001), hyperemic MBF (3.49±0.76 vs. 2.65±0.72 ml/min/g, p<0.0001), and PR (3.19±0.78 vs. 2.93±0.89, p = 0.03) in women. Correlations between pericardial fat and clinical and hemodynamic variables were stronger in women. In women only (p = 0.01 for gender interaction) higher pericardial fat was associated with higher resting MBF (p = 0.008). However, this association was attenuated after accounting for body mass index or rate-pressure product. There were no significant associations between pericardial fat and hyperemic MBF or PR after multivariate adjustment in either gender. In logistic regression analyses there was also no association between impaired coronary vasoreactivity, defined as having a PR <2.5, and pericardial fat in men (OR, 1.18; 95% CI, 0.82–1.70) or women (OR, 1.11; 95% CI, 0.68–1.82).

Conclusions

Our data fail to support an independent association between pericardial fat and myocardial perfusion in adults without symptomatic cardiovascular disease. Nevertheless, these findings highlight potentially important differences between asymptomatic and symptomatic individuals with respect to the underlying subclinical disease burden.

Coronary risk factors and myocardial blood flow in patients evaluated for coronary artery disease: a quantitative [15O]H2O PET/CT study

BACKGROUND

There has been increasing interest in quantitative myocardial blood flow (MBF) imaging over the last years and it is expected to become a routinely used technique in clinical practice. Positron emission tomography (PET) using [(15)O]H(2)O is the established gold standard for quantification of MBF in vivo. A fundamental issue when performing quantitative MBF imaging is to define the limits of MBF in a clinically suitable population. The aims of the present study were to determine the limits of MBF and to determine the relationship among coronary artery disease (CAD) risk factors, gender and MBF in a predominantly symptomatic patient cohort without significant CAD.

METHODS

A total of 128 patients (mean age 54 ± 10 years, 50 men) with a low to intermediate pretest likelihood of CAD were referred for noninvasive evaluation of CAD using a hybrid PET/computed tomography (PET/CT) scanner. MBF was quantified with [(15)O]H(2)O at rest and during adenosine-induced hyperaemia. Obstructive CAD was excluded in these patients by means of invasive or CT-based coronary angiography.

RESULTS

Global average baseline MBF values were 0.91 ± 0.34 and 1.09 ± 0.30 ml·min(-1)·g(-1) (range 0.54-2.35 and 0.59-2.75 ml·min(-1)·g(-1)) in men and women, respectively (p < 0.01). However, no gender-dependent difference in baseline MBF was seen following correction for rate-pressure product (0.98 ± 0.45 and 1.09 ± 0.30 ml·min(-1)·g(-1) in men and women, respectively; p = 0.08). Global average hyperaemic MBF values were 3.44 ± 1.20 ml·min(-1)·g(-1) in the whole study population, and 2.90 ± 0.85 and 3.78 ± 1.27 ml·min(-1)·g(-1) (range 1.52-5.22 and 1.72-8.15 ml·min(-1)·g(-1)) in men and women, respectively (p < 0.001). Multivariate analysis identified male gender, age and body mass index as having an independently negative impact on hyperaemic MBF.

CONCLUSION

Gender, age and body mass index substantially influence reference values and should be corrected for when interpreting hyperaemic MBF values.

Silent myocardial ischaemia and long-term coronary artery disease outcomes in apparently healthy people from families with early-onset ischaemic heart disease

AIMS

A family history of premature coronary artery disease (CAD) in an apparently healthy individual conveys an increased risk of future CAD. The extent to which inducible myocardial ischaemia exists and is associated with long-term incident CAD in apparently healthy siblings of early-onset CAD patients is unknown.

METHODS AND RESULTS

Asymptomatic siblings (n = 1287, aged 30-59 years) of patients with onset of CAD <60 years of age underwent risk factor screening and maximal graded treadmill testing with nuclear perfusion imaging, and were followed for incident CAD events for up to 25 years. Incident CAD occurred in 15.2% of siblings (68% acute coronary syndromes); mean time to first CAD event was 8.2 ± 5.2 years. Inducible ischaemia was highly prevalent in male siblings (26.9%), and was independently associated with incident CAD. Male siblings ≥ 40 years of age who were low or intermediate risk by traditional risk assessment, had a prevalence of inducible ischaemia and a 10-year risk of incident CAD that were near or ≥ 20%. In female siblings ≥ 40 years of age, the presence of inducible ischaemia was also independently associated with incident CAD, but the prevalence of inducible ischaemia was markedly lower, as was the risk of incident CAD.

CONCLUSION

Inducible ischaemia is highly prevalent in male siblings, suggesting a previously unknown long quiescent period before the occurrence of a clinical event. While inducible ischaemia is associated with a worse prognosis, male siblings with negative tests still bear a high risk of incident disease, such that we propose that in male siblings over 40 years of age, aggressive primary prevention interventions be instituted without nuclear testing. For women, the prevalence of ischaemia was so low as to not warrant screening, but the incidence of CAD was high enough to at least warrant lifestyle interventions.

Combination rosuvastatin plus fenofibric acid in a cohort of patients 65 years or older with mixed dyslipidemia: subanalysis of two randomized, controlled studies

BACKGROUND

Coronary heart disease risk increases with advancing age and is further increased in patients with mixed dyslipidemia, characterized by elevated low-density lipoprotein cholesterol (LDL-C), low high-density lipoprotein cholesterol (HDL-C), and high triglycerides (TG). Combination lipid therapy is an option; however, efficacy and safety data among elderly patients are lacking.

HYPOTHESIS

The combination of rosuvastatin and fenofibric acid (R + FA) results in more comprehensive lipid improvements than corresponding-dose monotherapies, without additional safety concerns, in elderly patients with mixed dyslipidemia.

METHODS

This post-hoc analysis evaluated data from patients age ≥ 65 years (n = 401) with mixed dyslipidemia (LDL-C ≥ 130 mg/dL, HDL-C < 40 mg/dL [men] or < 50 mg/dL [women], and TG ≥ 150 mg/dL) in 2 randomized studies. Patients included in this analysis received either monotherapy (as R 5, 10, or 20 mg or FA 135 mg), or combination therapy with R (5, 10, or 20 mg) + FA 135 mg, for 12 weeks. Data were pooled and analyzed, and mean/median percent changes in multiple lipid parameters and biomarkers were compared.

RESULTS

Combination therapy decreased LDL-C by 31.8%-47.2% vs 10.6% with FA monotherapy (P < 0.001). Combination therapy also increased HDL-C by 21.9%-27.0% vs 5.9%-9.9% with R monotherapy (P < 0.001), and decreased TG by 48.3%-53.5% vs 20.7%-32.8% with R monotherapy (P < 0.001). In general, safety profiles were consistent between combination therapy and individual monotherapies.

CONCLUSIONS

In these elderly patients with mixed dyslipidemia, R 5, 10, or 20 mg in combination with FA 135 mg improved the overall lipid profile, without new or unexpected safety issues.

Comparison of myocardial perfusion estimates from dynamic contrast-enhanced magnetic resonance imaging with four quantitative analysis methods

Dynamic contrast-enhanced MRI has been used to quantify myocardial perfusion in recent years. Published results have varied widely, possibly depending on the method used to analyze the dynamic perfusion data. Here, four quantitative analysis methods (two-compartment modeling, Fermi function modeling, model-independent analysis, and Patlak plot analysis) were implemented and compared for quantifying myocardial perfusion. Dynamic contrast-enhanced MRI data were acquired in 20 human subjects at rest with low-dose (0.019 +/- 0.005 mmol/kg) bolus injections of gadolinium. Fourteen of these subjects were also imaged at adenosine stress (0.021 +/- 0.005 mmol/kg). Aggregate rest perfusion estimates were not significantly different between all four analysis methods. At stress, perfusion estimates were not significantly different between two-compartment modeling, model-independent analysis, and Patlak plot analysis. Stress estimates from the Fermi model were significantly higher (approximately 20%) than the other three methods. Myocardial perfusion reserve values were not significantly different between all four methods. Model-independent analysis resulted in the lowest model curve-fit errors. When more than just the first pass of data was analyzed, perfusion estimates from two-compartment modeling and model-independent analysis did not change significantly, unlike results from Fermi function modeling.

Assessment of advanced coronary artery disease: advantages of quantitative cardiac magnetic resonance perfusion analysis

OBJECTIVES

The purpose of this paper was to compare quantitative cardiac magnetic resonance (CMR) first-pass contrast-enhanced perfusion imaging to qualitative interpretation for determining the presence and severity of coronary artery disease (CAD).

BACKGROUND

Adenosine CMR can detect CAD by measuring perfusion reserve (PR) or by qualitative interpretation (QI).

METHODS

Forty-one patients with an abnormal nuclear stress scheduled for X-ray angiography underwent dual-bolus adenosine CMR. Segmental myocardial perfusion analyzed using both QI and PR by Fermi function deconvolution was compared to quantitative coronary angiography.

RESULTS

In the 30 patients with complete quantitative data, PR (mean +/- SD) decreased stepwise as coronary artery stenosis (CAS) severity increased: 2.42 +/- 0.94 for <50%, 2.14 +/- 0.87 for 50% to 70%, and 1.85 +/- 0.77 for >70% (p < 0.001). The PR and QI had similar diagnostic accuracies for detection of CAS >50% (83% vs. 80%), and CAS >70% (77% vs. 67%). Agreement between observers was higher for quantitative analysis than for qualitative analysis. Using PR, patients with triple-vessel CAD had a higher burden of detectable ischemia than patients with single-vessel CAD (60% vs. 25%; p = 0.02), whereas no difference was detected by QI (31% vs. 21%; p = 0.26). In segments with myocardial scar (n = 64), PR was 3.10 +/- 1.34 for patients with CAS <50% (n = 18) and 1.91 +/- 0.96 for CAS >50% (p < 0.0001).

CONCLUSIONS

Quantitative PR by CMR differentiates moderate from severe stenoses in patients with known or suspected CAD. The PR analysis differentiates triple- from single-vessel CAD, whereas QI does not, and determines the severity of CAS subtending myocardial scar. This has important implications for assessment of prognosis and therapeutic decision making.

Hypertension impairs myocardial blood perfusion reserve in subjects without regional myocardial ischemia

Quantitative analysis of myocardial perfusion MRI can provide noninvasive assessments of myocardial perfusion reserve (MPR), which is associated with endothelial function. Endothelial function is influenced by various factors, including hypertension, diabetes, dyslipidemia, renal dysfunction and anemia. The purpose of this study was to evaluate which risk factor is the strongest effector of MPR in subjects without regional myocardial ischemia. We studied 110 patients (66 years ±10, male 68%, hypertension 76%, diabetes mellitus (DM) 40% and dyslipidemia 65%) without regional myocardial ischemia. Adenosine triphosphate (ATP) stress and rest first-pass perfusion magnetic resonance (MR) images were acquired with a 1.5-T MR system, and MPR was calculated as the ratio of stress to rest myocardial blood flow (MBF). Average rest MBF in 110 patients was 1.07±0.62 ml min⁻¹ g⁻¹, whereas stress MBF was 3.15±1.93 ml min⁻¹ g⁻¹ and the MPR was 3.33±1.82. Rest MBF correlated significantly with hematocrit, whereas stress MBF showed a strong correlation with estimated glomerular filtration rate (e-GFR). MPR was associated with hypertension, age, e-GFR, hematocrit and left ventricular mass index (LVMI). In multiple regression analysis, hypertension (P=0.003, β=-0.274) showed the strongest correlation with MPR among other risk factors, such as diabetes (P=ns), dyslipidemia (P=ns), e-GFR (P=ns), LVMI (P=0.007, β=-0.248) and hematocrit (P=ns) after adjusting age and gender. Hypertension is the most important effector of MPR in subjects without myocardial ischemia.

Myocardial perfusion scintigraphy in asymptomatic diabetic patients: a critical review

The increasing prevalence of diabetes mellitus and the associated high cardiovascular risk has made the non-invasive identification of silent coronary heart disease in diabetic individuals an important issue. This strategy could identify higher risk asymptomatic patients with diabetes mellitus in whom coronary revascularization may improve the outcome beyond that achieved by currently recommended medical management. Stress myocardial perfusion imaging has been shown to be effective in detecting coronary heart disease and predicting adverse cardiac events in asymptomatic diabetic patients. However, the clinical utility of myocardial perfusion scintigraphy is debated intensively due to the paucity of prospective and outcome based evidence. The controversy stems from several observational studies, epidemiologic data and cost-effectiveness analyses. Thus, although several authors and professional organizations advocate the use of stress imaging for screening higher risk asymptomatic diabetic patients, others are cautious in recommending any kind of stress testing in that population. This review is based on a broad survey of the literature and discusses the potential role of stress myocardial perfusion scintigraphy in screening asymptomatic diabetic subjects for coronary heart disease in the current era and in relation with other non-invasive screening tools.

Role of endogenous ET-1 in the regulation of myocardial blood flow in lean and obese humans

Endothelin is an important determinant of peripheral vascular tone, and increased endogenous endothelin activity contributes to peripheral vascular dysfunction in human obesity. The contributions of endothelin to the regulation of coronary vascular tone in health in humans have not been well studied. We hypothesized that the contribution of endothelin to the regulation of myocardial perfusion would be augmented in human obesity. Using [NH(3)]ammonia positron emission tomography (PET), we measured myocardial perfusion under resting and adenosine-stimulated conditions on two separate days, with and without concurrent exposure to BQ123, an antagonist of type A endothelin receptors (1 micromol/min IV beginning 90 min before measurement). We studied 10 lean and 9 obese subjects without hypertension, hyperlipidemia, or diabetes mellitus. We observed a BQ123-induced increase in resting myocardial perfusion of approximately 40%, not different between lean and obese subjects (BQ123-induced increase in flow: lean 0.12 +/- 0.20, obese 0.32 +/- 0.51 ml/g/min, P = 0.02 BQ123 effect, P = 0.27 comparing response across groups). Although basal flow rates varied by region of the myocardium, the BQ123 effect was seen in all regions. BMI and cholesterol were significantly related to BQ123-induced increases in basal tone in multivariable analysis. There was no baseline difference in the adenosine-stimulated increase in blood flow between lean and obese subjects, and BQ123 failed to augment these responses in either group. These observations suggest that endothelin is an important contributor to the regulation of myocardial perfusion under resting conditions in healthy lean and obese humans, with increased contributions in proportion to increasing obesity.

Comprehensive adenosine stress perfusion MRI defines the etiology of chest pain in the emergency room: Comparison with nuclear stress test

PURPOSE

To compare standard of care nuclear SPECT imaging with cardiac magnetic resonance imaging (MRI) for emergency room (ER) patients with chest pain and intermediate probability for coronary artery disease.

MATERIALS AND METHODS

Thirty-one patients with chest pain, negative electrocardiogram (ECG), and negative cardiac enzymes who underwent cardiac single photon emission tomography (SPECT) within 24 h of ER admission were enrolled. Patients underwent a comprehensive cardiac MRI exam including gated cine imaging, adenosine stress and rest perfusion imaging and delayed enhancement imaging. Patients were followed for 14 +/- 4.7 months.

RESULTS

Of 27 patients, 8 (30%) showed subendocardial hypoperfusion on MRI that was not detected on SPECT. These patients had a higher rate of diabetes (P = 0.01) and hypertension (P = 0.01) and a lower global myocardial perfusion reserve (P = 0.01) compared with patients with a normal cardiac MRI (n = 10). Patients with subendocardial hypoperfusion had more risk factors for cardiovascular disease (mean 4.4) compared with patients with a normal MRI (mean 2.5; P = 0.005). During the follow-up period, patients with subendocardial hypoperfusion on stress MRI were more likely to return to the ER with chest pain compared with patients who had a normal cardiac MRI (P = 0.02). Four patients did not finish the MR exam due to claustrophobia.

CONCLUSION

In patients with chest pain, diabetes and hypertension, cardiac stress perfusion MRI identified diffuse subendocardial hypoperfusion defects in the ER setting not seen on cardiac SPECT, which is suspected to reflect microvascular disease.

Quantitative analysis of first-pass contrast-enhanced myocardial perfusion MRI using a Patlak plot method and blood saturation correction

The objectives of this study were to develop a method for quantifying myocardial K(1) and blood flow (MBF) with minimal operator interaction by using a Patlak plot method and to compare the MBF obtained by perfusion MRI with that from coronary sinus blood flow in the resting state. A method that can correct for the nonlinearity of the blood time-signal intensity curve on perfusion MR images was developed. Myocardial perfusion MR images were acquired with a saturation-recovery balanced turbo field-echo sequence in 10 patients. Coronary sinus blood flow was determined by phase-contrast cine MRI, and the average MBF was calculated as coronary sinus blood flow divided by left ventricular (LV) mass obtained by cine MRI. Patlak plot analysis was performed using the saturation-corrected blood time-signal intensity curve as an input function and the regional myocardial time-signal intensity curve as an output function. The mean MBF obtained by perfusion MRI was 86 +/- 25 ml/min/100 g, showing good agreement with MBF calculated from coronary sinus blood flow (89 +/- 30 ml/min/100 g, r = 0.74). The mean coefficient of variation for measuring regional MBF in 16 LV myocardial segments was 0.11. The current method using Patlak plot permits quantification of MBF with operator interaction limited to tracing the LV wall contours, registration, and time delays.

Increased left ventricular torsion in uncomplicated type 1 diabetic patients: the role of coronary microvascular function

OBJECTIVE

We used speckle tracking echocardiography to study the early changes in left ventricular (LV) torsion in young patients with uncomplicated type 1 diabetes and stress magnetic resonance imaging (MRI) to assess its interrelationships with coronary microangiopathy.

RESEARCH DESIGN AND METHODS

We recruited 33 asymptomatic subjects with type 1 diabetes and 32 age-matched healthy control subjects. All subjects underwent echocardiograms. Stress MRIs were performed in 30 subjects (8 healthy control subjects) to compute myocardial perfusion reserve index (MPRI).

RESULTS

A significant increase in LV torsion (2 +/- 0.7 vs. 1.4 +/- 0.7 degrees /cm, P < 0.05) was identified in longer-term and retinopathy-positive type 1 diabetic subjects (1.9 +/- 0.7 vs. 1.4 +/- 0.7 degrees /cm, P < 0.05) as compared with the healthy control subjects. The MPRI was independently associated with increased LV torsion.

CONCLUSIONS

We demonstrate that LV torsion is increased in young patients with uncomplicated type 1 diabetes and that coronary microvascular disease may play a key pathophysiological role in the development of increased LV torsion.

Quantification of absolute myocardial blood flow by magnetic resonance perfusion imaging

By serially imaging the myocardium during the initial transit of gadolinium contrast, magnetic resonance perfusion imaging can accurately assess relative reductions in regional myocardial blood flow and identify hemodynamically significant coronary artery disease. Models can be used to quantify myocardial blood flow (in milliliters/minute/gram) on the basis of dynamic signal changes within the myocardium and left ventricular cavity. Although the mathematical modeling involved in this type of analysis adds complexity, the benefits of absolute blood flow quantification might improve clinical diagnosis and have important implications for cardiovascular research.

Percutaneous treatment of chronic total coronary occlusions improves regional hyperemic myocardial blood flow and contractility: insights from quantitative cardiovascular magnetic resonance imaging

OBJECTIVES

We sought to investigate temporal changes in contractility and hyperemic and resting myocardial blood flow (MBF) in dependent and remote myocardium after percutaneous coronary intervention (PCI) of chronic total occlusions (CTOs) by using cardiovascular magnetic resonance (CMR) imaging.

BACKGROUND

Data about the physiological consequences of revascularization of CTOs are limited. The use of CMR allows investigation of the regional effects of revascularization on MBF and left ventricular contractility.

METHODS

We prospectively recruited 3 patient groups: 17 patients scheduled for CTO PCI, 17 scheduled for PCI of a stenosed but nonoccluded coronary artery (non-CTO), and 6 patients with CTO who were not scheduled for revascularization. All patients undergoing PCI underwent CMR imaging <24 h before PCI, with repeat CMR imaging 24 h and 6 months after PCI. Each CMR scan consisted of cine, perfusion, and delayed enhancement imaging. Regional hyperemic and resting MBF, wall thickening, and transmural extent of infarction were calculated.

RESULTS

In both intervention groups, hyperemic MBF in treated segments increased 24 h after PCI compared with baseline: CTO group, 2.1 +/- 0.2 ml/min/g versus 1.4 +/- 0.2 ml/min/g (p < 0.01); non-CTO group, 2.5 +/- 0.2 ml/min/g versus 1.6 +/- 0.2 ml/min/g (p < 0.01). This improvement persisted 6 months after PCI (p < 0.01 for both groups). Contractility in treated segments was improved at 24 h and 6 months after CTO PCI but only at 6 months after non-CTO PCI. In both intervention groups, treated segments no longer had reduced MBF or contractility compared with remote segments. In patients with untreated CTO segments, MBF and wall thickening did not improve at follow-up.

CONCLUSIONS

Successful CTO PCI increases hyperemic MBF as early as 24 h after the procedure, with a greater and earlier improvement in regional contractility than after non-CTO PCI, despite a greater likelihood of irreversible injury in CTO segments.

Vascular dysfunction measured by fingertip thermal monitoring is associated with the extent of myocardial perfusion defect

BACKGROUND

Previous studies have shown that vascular dysfunction measured by digital thermal monitoring (DTM) during an arm-cuff reactive hyperemia procedure correlates with the severity of coronary artery disease measured by coronary artery calcium in asymptomatic patients. Current study investigates the correlation between DTM and abnormal myocardial perfusion imaging (MPI).

METHODS

About 116 consecutive patients with chest discomfort, age 57 +/- 10 years, underwent MPI, DTM and Framingham Risk Score (FRS) assessment. Fingertip temperature rebound (TR), DTM index of vascular reactivity, was assessed after a 2-minute arm-cuff reactive hyperemia test. The extent of myocardial perfusion defect was measured by summed stress score (SSS).

RESULTS

TR decreased from SSS < 4 (1.61 +/- 0.15) to 4 < or = SSS < or = 8 (0.5 +/- 0.22) to 9 < or = SSS < or = 13 (0.26 +/- 0.15) to SSS > 13 (-0.37 +/- 0.19) (P = .0001). After adjusting for cardiac risk factors, the odds ratio of the lowest versus two upper tertiles of TR was 3.93 for SSS > or = 4 and 9.65 for SSS > or = 8 compared to SSS < 4. TR correlated well with SSS (r = -0.88, P = .0001). Addition of TR to FRS increased the area under the ROC curve to predict abnormal MPI, SSS > or = 4, from 0.65 to 0.84 (P < .05).

CONCLUSION

Vascular dysfunction measured by DTM is associated with the extent of myocardial perfusion defect independent of age, gender, and cardiac risk factors.

First-pass dynamic contrast-enhanced MRI with extravasating contrast reagent: evidence for human myocardial capillary recruitment in adenosine-induced hyperemia

Human myocardial (1)H(2)O T(1)-weighted dynamic contrast-enhanced MRI data were acquired during the brief first-pass period after injection of a very small gadolinium diethylenetriaminepenta-acetate (GdDTPA(2-)) dose. The shutter-speed pharmacokinetic effects of both transendothelial and transcytolemmal equilibrium water exchange processes were investigated. Our results indicate that even for such a short acquisition window and relatively large pseudo-first-order rate constant (K(trans)) for plasma/interstitium contrast reagent (CR) transfer the kinetics of these water exchange processes cannot be treated as infinitely fast or slow. However, neither the intracellular water molecule lifetime (tau(i)) nor its intravascular counterpart (tau(b)) are among the parameters most influential in analysis of the noisy data typically associated with the cardiac perfusion application. Thus, the actual values of water exchange kinetic rate constants are relatively indeterminate as this experiment is usually conducted. Combining the K(trans) evaluations with independently determined flow (F) values allows us to estimate CR permeability coefficient surface area product (P(CR)S) values. The fact that the P(CR)S magnitudes almost equal the K(trans) values confirms that GdDTPA(2-) extravasation in resting human myocardial muscle is indeed permeation-limited and supports the validity of the K(trans) and P(CR)S estimations. Nevertheless the model analysis is most consistent with the results if P(CR)S is not assumed to be constant with changing flow. The capillary blood volume fraction (v(b)) is a sensitive parameter in the analysis. We also compared resting and hyperemic cardiac conditions, the latter resulting from the volume flow increase induced by adenosine arteriolar vasodilation. We found that the P(CR)S value increases with flow probably mostly because of an S increase associated with capillary recruitment. The v(b) values also increased in hyperemia and showed a flow-dependence with a clearly identifiable component due to capillary recruitment.

Diabetic cardiomyopathy

Diabetes mellitus is well recognized as a potent and prevalent risk factor for accelerated atherosclerosis and ischemic heart disease. However, there is also evidence of cardiac dysfunction in diabetes in the absence of coronary atherosclerosis, termed diabetic cardiomyopathy. Changes in ventricular structure and left ventricular systolic and diastolic dysfunction have all been noted even in patients with well-controlled diabetes and without overt macrovascular complications. Insulin resistance, hyperglycemia, and increased free fatty acid metabolism promote coronary microvascular disease, sympathetic nervous system dysfunction, and ventricular remodeling, and may contribute to the altered cardiac phenotype seen in diabetes. In addition to standard therapy (angiotensin-converting enzyme inhibitors and beta-blockers), diabetic patients with left ventricular dysfunction are likely to benefit from targeted therapies to reduce insulin resistance and modulate substrate use.

Estimating myocardial perfusion from dynamic contrast-enhanced CMR with a model-independent deconvolution method

BACKGROUND

Model-independent analysis with B-spline regularization has been used to quantify myocardial blood flow (perfusion) in dynamic contrast-enhanced cardiovascular magnetic resonance (CMR) studies. However, the model-independent approach has not been extensively evaluated to determine how the contrast-to-noise ratio between blood and tissue enhancement affects estimates of myocardial perfusion and the degree to which the regularization is dependent on the noise in the measured enhancement data. We investigated these questions with a model-independent analysis method that uses iterative minimization and a temporal smoothness regularizer. Perfusion estimates using this method were compared to results from dynamic 13N-ammonia PET.

RESULTS

An iterative model-independent analysis method was developed and tested to estimate regional and pixelwise myocardial perfusion in five normal subjects imaged with a saturation recovery turboFLASH sequence at 3 T CMR. Estimates of myocardial perfusion using model-independent analysis are dependent on the choice of the regularization weight parameter, which increases nonlinearly to handle large decreases in the contrast-to-noise ratio of the measured tissue enhancement data. Quantitative perfusion estimates in five subjects imaged with 3 T CMR were 1.1 +/- 0.8 ml/min/g at rest and 3.1 +/- 1.7 ml/min/g at adenosine stress. The perfusion estimates correlated with dynamic 13N-ammonia PET (y = 0.90x + 0.24, r = 0.85) and were similar to results from other validated CMR studies.

CONCLUSION

This work shows that a model-independent analysis method that uses iterative minimization and temporal regularization can be used to quantify myocardial perfusion with dynamic contrast-enhanced perfusion CMR. Results from this method are robust to choices in the regularization weight parameter over relatively large ranges in the contrast-to-noise ratio of the tissue enhancement data.

Fully automated motion correction in first-pass myocardial perfusion MR image sequences

This paper presents a novel method for registration of cardiac perfusion magnetic resonance imaging (MRI). The presented method is capable of automatically registering perfusion data, using independent component analysis (ICA) 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 that ICA. This reference image is used in a two-pass registration framework. Qualitative and quantitative validation of the method is carried out using 46 clinical quality, short-axis, perfusion MR datasets comprising 100 images each. Despite varying image quality and motion patterns in the evaluation set, validation of the method showed a reduction of the average right ventricle (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. Comparison of clinically relevant parameters computed using registered data and the manual gold standard show a good agreement. Additional tests with a simulated free-breathing protocol showed robustness against considerable deviations from a standard breathing protocol. We conclude that this fully automatic ICA-based method shows an accuracy, a robustness and a computation speed adequate for use in a clinical environment.

Stress perfusion magnetic resonance imaging of the heart

Extensive research has documented that rapid imaging during the first pass of a magnetic resonance imaging (MRI) contrast agent provides good sensitivity to detect myocardial blood flow deficits caused by coronary disease, cardiomyopathies, or microvascular dysfunction in patients without obstructive lesions in the coronary arteries. The autoregulatory mechanisms of the coronary circulation serve the purpose of maintaining sufficient blood flow at baseline in the presence of flow-obstructing coronary lesions. Stress testing is most commonly used in this setting to determine the hemodynamic effect of coronary lesions in the epicardial arteries when the small-vessel resistance has been minimized by vasodilation. The protocols for perfusion MRI combined with vasodilation have been successfully tested in large patient studies. Besides the absence of any ionizing radiation, MRI offers the advantages of relatively high spatial resolution to detect perfusion defects limited to the inner layer of the heart muscle. Furthermore, MRI can be used for noninvasive quantitative measurements of myocardial blood flow that compare well with invasive measurements with labeled microspheres. Additional useful markers, such as the dynamic distribution volume, the delay in the arrival of the contrast agent in a myocardial region relative to the enhancement in the arterial input, and the capillary permeability-surface area product, may, in the future, further enhance the capabilities to characterize with MRI coronary atherosclerosis, coronary vascular dysfunction, and adaptive mechanisms in the coronary circulation, such as arteriogenesis, that reduce ischemia.

Nonlinear myocardial signal intensity correction improves quantification of contrast-enhanced first-pass MR perfusion in humans

PURPOSE

To study the nonlinearity of myocardial signal intensity and gadolinium contrast concentration during first-pass perfusion MRI, and to compare quantitative perfusion estimates using nonlinear myocardial signal intensity correction.

MATERIALS AND METHODS

The nonlinearity of signal intensity and contrast concentration was simulated by magnetization modeling and evaluated in phantom measurements. A total of 10 healthy volunteers underwent rest and stress dual-bolus perfusion studies using an echo-planar imaging sequence at both short and long saturation-recovery delay times (TD70 and TD150). Perfusion estimates were compared before and after the correction.

RESULTS

The phantom data showed a linear relationship (R(2) = 1.00 and 0.99) of corrected signal intensity vs. contrast concentrations. Peak myocardial contrast concentration averaged 0.64 +/- 0.10 mmol x L(-1) at rest and 0.91 +/- 0.21 mmol x L(-1) during stress for TD70 and were similar for TD150 (P = not significant [NS]). The corrections were larger for stress than rest perfusion and larger for TD150 than TD70 studies (both P < 0.01). Perfusion estimates of TD70 and TD150 stress studies were significantly different before the correction (P < 0.01) but equivalent after the correction (P = NS).

CONCLUSION

The nonlinearity between signal intensity and myocardial contrast concentration in perfusion MRI can be corrected through magnetization modeling. A nonlinear correction of myocardial signal intensity is feasible and improves quantitative perfusion analysis.

Noninvasive assessment of coronary vasodilation using cardiovascular magnetic resonance in patients at high risk for coronary artery disease

BACKGROUND

Impaired coronary vasodilation to both endothelial-dependent and endothelial-independent stimuli have been associated with atherosclerosis. Direct measurement of coronary vasodilation using x-ray angiography or intravascular ultrasound is invasive and, thus, not appropriate for asymptomatic patients or for serial follow-up. In this study, high-resolution coronary cardiovascular magnetic resonance (CMR) was used to investigate the vasodilatory response to nitroglycerine (NTG) of asymptomatic patients at high risk for CAD.

METHODS

A total of 46 asymptomatic subjects were studied: 13 high-risk patients [8 with diabetes mellitus (DM), 5 with end stage renal disease (ESRD)] and 33 age-matched controls. Long-axis and cross-sectional coronary artery images were acquired pre- and 5 minutes post-sublingual NTG using a sub-mm-resolution multi-slice spiral coronary CMR sequence. Coronary cross sectional area (CSA) was measured on pre- and post-NTG images and % coronary vasodilation was calculated.

RESULTS

Patients with DM and ESRD had impaired coronary vasodilation to NTG compared to age-matched controls (17.8 +/- 7.3% vs. 25.6 +/- 7.1%, p = 0.002). This remained significant for ESRD patients alone (14.8 +/- 7.7% vs. 25.6 +/- 7.1%; p = 0.003) and for DM patients alone (19.8 +/- 6.3% vs. 25.6 +/- 7.1%; p = 0.049), with a non-significant trend toward greater impairment in the ESRD vs. DM patients (14.8 +/- 7.7% vs. 19.8 +/- 6.3%; p = 0.23).

CONCLUSION

Noninvasive coronary CMR demonstrates impairment of coronary vasodilation to NTG in high-risk patients with DM and ESRD. This may provide a functional indicator of subclinical atherosclerosis and warrants clinical follow up to determine prognostic significance.

Coronary flow reserve is impaired in patients with aortic valve calcification

BACKGROUND

Calcific aortic valve disease is an active and progressive condition. Data indicate that aortic valve calcification (AVC) is associated with endothelial dysfunction and accepted as a manifestation of atherosclerosis. Coronary flow reserve (CFR) determined by transthoracic echocardiography has been introduced as a reliable indicator for coronary microvascular function. In this study we aimed to evaluate CFR in patients with AVC.

METHODS

Eighty patients, aged more than 60 years, without coronary heart disease or diabetes mellitus were included: 40 had AVC without significant stenosis (peak gradient across the valve <25 mm Hg) and 40 had normal aortic valves (controls). Using transthoracic Doppler echocardiography, we measured coronary diastolic peak flow velocities (PFV) at baseline and after dipyridamole infusion. CFR was calculated as the ratio of hyperemic to baseline diastolic PFV and was compared between groups.

RESULTS

Mean ages for patients with AVC and controls were 68.9+/-6.2 and 67.6+/-5.9 years (P=.3). There were no significant differences regarding clinical characteristics, laboratory findings, ejection fraction, or peak aortic valve gradients. Mean diastolic PFV at baseline and during hyperemia were 28.4+/-4.2 and 59.2+/-7.8 cm/s for AVC and 27.7+/-3.9 and 68.5+/-10.5 cm/s for controls. Compared with controls, patients with AVC had significantly lower CFR values (2.12+/-0.41 versus 2.51+/-0.51; P<.0001).

CONCLUSION

CFR is impaired in patients with AVC before valve stenosis develops, suggesting that microvascular-endothelial dysfunction is present during the early stages of the calcific aortic valve disease.

Coronary flow reserve is impaired in subclinical hypothyroidism

OBJECTIVE

Although the cardiovascular system is highly sensitive to thyroid hormones, the cardiovascular effects of subtle thyroid dysfunction such as subclinical hypothyroidism (SHT) remain unclear. Therefore, we investigated coronary flow reserve (CFR) reflecting coronary microvascular function in patients with SHT.

METHODS

Fifty subjects with SHT and 30 control subjects with normal serum thyroid hormones and TSH levels were included in this study. Coronary diastolic peak flow velocities were measured at baseline and after dipyridamole infusion. CFR was calculated as the ratio of hyperemic to baseline diastolic peak velocity.

RESULTS

Age, gender, diastolic and systolic blood pressure, body mass index (BMI), serum lipid parameters, and thyroid hormone levels were similar between the groups. Heart rate was significantly lower in the SHT group. Left ventricular diastolic filling parameters were significantly different in the SHT group while other echocardiographic parameters were similar. CFR values were significantly lower in subjects with SHT than in the control group (2.38 +/- 0.44 vs. 2.98 +/- 0.47, p < 0.0001).

CONCLUSIONS

These findings suggest that CFR, which reflects coronary microvascular function, is impaired in patients with SHT.

Impaired coronary microvascular and left ventricular diastolic functions in patients with ankylosing spondylitis

BACKGROUND

It has been shown that the patients with inflammatory rheumatic diseases such as systemic lupus erythematosus and rheumatoid arthritis have an increased risk of developing atherosclerosis. However, the association of ankylosing spondylitis (AS) to atherosclerosis and related diseases is still controversial. Accordingly, we investigated coronary flow reserve (CFR) and left ventricular (LV) diastolic function in patients with AS using transthoracic Doppler echocardiography.

METHODS

CFR and LV diastolic function were studied in 40 patients with AS (38.9+/-10.2 years, 26 males) and 35 healthy volunteers (37.5+/-6.4 years, 23 males). Coronary diastolic peak flow velocities (DPFV) were measured at baseline and after dipyridamole infusion. CFR was calculated as the ratio of hyperemic to baseline DPFV. LV diastolic function was assessed by both standard and tissue Doppler imaging.

RESULTS

Demographic features and coronary risk factors except diastolic blood pressure were similar between the groups. CFR were significantly lower in the AS group than in the control group (2.20+/-0.46 versus 3.02+/-1.50, P<0.0001). Reflecting LV diastolic function mitral A-wave and E/A ratio were borderline significant, and mitral E-wave deceleration time and isovolumic relaxation time were significantly different between the groups. Serum hsCRP and TNF-alpha levels were significantly higher in the patients with AS, and hsCRP and TNF-alpha levels independently correlated with CFR.

CONCLUSION

These findings show that CFR reflecting coronary microvascular function and LV diastolic function are impaired in patients with AS, and severity of these impairments correlate well with hsCRP and TNF-alpha. These results suggest that impaired CFR may be an early manifestation of cardiac involvement in patients with AS.

Relationship between retinal arteriolar narrowing and myocardial perfusion: multi-ethnic study of atherosclerosis

Retinal arteriolar narrowing is a marker of chronic hypertension. Myocardial perfusion reflects microvascular processes in the heart. The relationship between these 2 measures has not been studied previously and is examined in 212 men and women aged 45 to 84 years and free of cardiovascular disease diagnoses. Retinal caliber was measured through fundus photography and presented as central retinal arteriolar and venular caliber equivalents. Myocardial blood flow was measured using MRI during rest and adenosine-induced hyperemia. Among subjects with no coronary artery calcification (n=98), smaller retinal arteriolar caliber was associated with lower hyperemic myocardial blood flow and perfusion reserve (calculated as the ratio of hyperemic:resting blood flow). Mean hyperemic blood flow (3.43, 3.28, 3.26, and 3.09 mL/min per gram; P(linear)=0.006) and mean perfusion reserve (3.52, 3.37, 3.19, and 3.10; P(linear)=0.01) progressively decreased across decreasing quartiles of retinal arteriolar caliber. These associations remained significant after adjusting for age, gender, and race/ethnicity but were no longer significant after additionally adjusting for other cardiovascular risk factors. In contrast, among subjects with coronary calcification (n=114), retinal arteriolar caliber was not associated with hyperemic myocardial blood flow (P(linear)=0.73) or perfusion reserve (P(linear)=0.79). There were no associations between retinal venular caliber and perfusion measurements. We conclude that narrower retinal arterioles were associated with lower hyperemic myocardial blood flow and perfusion reserve in asymptomatic adults with no coronary calcification, which is partially mediated by traditional cardiovascular risk factors. This finding suggests that retinal arteriolar narrowing may serve as a marker of coronary microvascular disease.

Clinically Unrecognized Myocardial Infarction Detected at MR Imaging May Not Be Associated with Atherosclerosis

PURPOSE

To prospectively investigate whether there is support for the hypothesis that clinically unrecognized myocardial infarctions (UMIs) detected at magnetic resonance (MR) imaging have an atherosclerotic pathogenesis similar to that of recognized myocardial infarctions (RMIs).

MATERIALS AND METHODS

After ethics committee approval and informed consent were obtained, gadolinium-enhanced whole-body MR angiography and late-enhancement MR imaging were performed in 248 randomly chosen 70-year-old subjects (123 women, 125 men). Imaging included the aorta and the carotid, renal, and lower limb arteries to the ankle, but not the coronary arteries. Subjects with myocardial infarction (MI) scars at late-enhancement MR imaging were classified as having RMI (n=11) (those with a diagnosis of MI at the hospital) or UMI (n=49) (those without a diagnosis of MI at the hospital). The presence of 50% or higher luminal narrowing in any vessel at whole-body MR angiography was considered to represent significant atherosclerosis. Intima-media thickness of the common carotid artery was measured with ultrasonography. C-reactive protein level was measured, and coronary heart disease risk was estimated. Observers were blinded to any previous results. The chi2 test, analysis of variance, and Bonferroni correction were used for statistical analyses.

RESULTS

None of the measured parameters differed significantly between the group without MI scars and the UMI group, but parameters were significantly increased in the RMI group (P<.05) compared with those in the group without MI scars. Forty-two of 49 UMIs and nine of 11 RMIs were located within inferolateral segments of the left ventricle.

CONCLUSION

MR imaging-detected UMIs might have a different pathogenesis from that of RMIs or may have the same pathogenesis but may manifest at an earlier stage.

Diagnostic accuracy of quantitative cardiac MRI evaluation compared to stress single-photon-emission computed tomography

BACKGROUND

Cardiac MRI (cMRI) perfusion is a promising non-invasive tool to assess myocardial ischemia. The accuracy of quantitative cMRI perfusion has been recently demonstrated, but to date no previous study has compared this technique with stress single-photon-emission computed tomography (SPECT). The aim of this study was to evaluate the diagnostic accuracy of myocardial perfusion reserve (MPR) based on cMRI compared with SPECT.

METHODS

We examined 24 patients who underwent coronary angiography, stress SPECT and cMRI perfusion. Qualitative assessment of both SPECT and cMRI images, quantification of cMRI perfusion, and quantitative coronary angiography (QCA) were independently performed. MPR was calculated using Fermi deconvolution technique. Accuracy of quantitative and qualitative data was examined to detect > 50% diameter stenosis (DS) by QCA.

RESULTS

Qualitative analysis was obtained in 198 segments and quantitative analysis was performed in 171 segments. Significant coronary artery disease (CAD) was present in 81.8% of patients. Visual cMRI assessment yielded sensitivity of 74.4% and specificity of 79.4% to predict > 50%DS, while SPECT showed sensitivity of 67.4% and specificity of 81.3%. The sensitivity for SPECT in the right coronary artery territory and apex was low compared to cMRI. Sensitivity and specificity for detection of significant CAD were 89.5% and 46.6% for MPR (cutoff 1.92). Area under the curve was 0.75 for MPR (P < 0.01).

CONCLUSIONS

The diagnostic accuracy of qualitative examination of perfusion cardiac MRI and stress SPECT were comparable. The high sensitivity and low operator dependency of quantitative cMRI makes it an attractive tool to evaluate myocardial perfusion.