Myocardial Perfusion Imaging by Cardiovascular Magnetic Resonance: Research Progress and Current Implementation

Cardiovascular diseases pose a significant health and economic burden worldwide, with coronary artery disease still recognized as a major problem. It is closely associated with hypertension, diabetes, obesity, smoking, lack of exercise, poor diet, and excessive alcohol consumption, which may lead to macro- and microvascular abnormalities in the heart. Coronary artery stenosis reduces the local supply of oxygen and nutrients to the myocardium and results in reduced levels of myocardial perfusion, which can lead to more severe conditions and irreversible damage to myocardial tissues. Therefore, accurate evaluation of myocardial perfusion abnormalities in patients with these risk factors is critical. As technology advances, magnetic resonance myocardial perfusion imaging has become more accurate at evaluating the myocardial microcirculation and has shown a powerful ability to detect myocardial ischemia. The purpose of this review is to summarize the principle, research progress of acquisition and analysis, and clinical implementation of cardiovascular magnetic resonance (CMR) myocardial perfusion imaging.

Long-term outcomes and left ventricular diastolic function of sarcomere mutation-positive and mutation-negative patients with hypertrophic cardiomyopathy: a prospective cohort study

AIMS

Hypertrophic cardiomyopathy (HCM) is an inheritable disease that leads to sudden cardiac death and heart failure (HF). Sarcomere mutations (SMs) have been associated with HF. However, the differences in ventricular function between SM-positive and SM-negative HCM patients are poorly characterized.

METHODS AND RESULTS

Of the prospectively enrolled 374 unrelated HCM patients in Taiwan, 115 patients underwent both 91 cardiomyopathy-related gene screening and cardiovascular magnetic resonance (45.6 ± 10.6 years old, 76.5% were male). Forty pathogenic/likely pathogenic mutations were identified in 52 patients by next-generation sequencing. The SM-positive group were younger at first cardiovascular event (P = 0.04) and progression to diastolic HF (P = 0.02) with higher N-terminal pro-brain natriuretic peptide (NT-proBNP) [New York Heart Association (NYHA) Class III/IV symptoms with left ventricular ejection fraction > 55%] than the SM-negative group (P < 0.001). SM-positive patients had a greater extent of late gadolinium enhancement (P = 0.01), larger left atrial diameter (P = 0.03), higher normalized peak filling rate (PFR) and PFR ratio, and a greater reduction in global longitudinal strain than SM-negative patients (all P ≤ 0.01). During mean lifelong follow-up time (49.2 ± 15.6 years), SM-positive was a predictor of earlier HF (NYHA Class III/IV symptoms) after multivariate adjustment (hazard ratio 3.5; 95% confidence interval 1.3-9.7; P = 0.015).

CONCLUSION

SM-positive HCM patients had a higher extent of myocardial fibrosis and more severe ventricular diastolic dysfunction than those without, which may contribute to earlier onset of advanced HF, suggesting the importance of close surveillance and early treatment throughout life.

Introduction to Cardiovascular Magnetic Resonance: Technical Principles and Clinical Applications

Cardiovascular magnetic resonance (CMR) is a set of magnetic resonance imaging (MRI) techniques designed to assess cardiovascular morphology, ventricular function, myocardial perfusion, tissue characterization, flow quantification and coronary artery disease. Since MRI is a non-invasive tool and free of radiation, it is suitable for longitudinal monitoring of treatment effect and follow-up of disease progress. Compared to MRI of other body parts, CMR faces specific challenges from cardiac and respiratory motion. Therefore, CMR requires synchronous cardiac and respiratory gating or breath-holding techniques to overcome motion artifacts. This article will review the basic principles of MRI and introduce the CMR techniques that can be optimized for enhanced clinical assessment.

KEY WORDS

Cardiovascular MR • Coronary arteries • Flow quantification • Myocardial fibrosis • Myocardial perfusion • Myocardial scarring • Regional wall motion • Ventricular function.

Sensitivity of quantitative myocardial dynamic contrast-enhanced MRI to saturation pulse efficiency, noise and t1 measurement error: Comparison of nonlinearity correction methods

PURPOSE

To compare methods designed to minimize or correct signal nonlinearity in quantitative myocardial dynamic contrast-enhanced (DCE) MRI.

METHODS

DCE-MRI studies were simulated and data acquired in eight volunteers. Signal nonlinearity was corrected using either a dual-bolus approach or model-based correction using proton-density weighted imaging (conventional or dual-sequence acquisition) or T1 data (native or bookend). Scanning of healthy and infarcted myocardium at 3 T was simulated, including noise, saturation imperfection and T1 measurement error. Data were analyzed using model-based deconvolution with a one-compartment (mono-exponential) model.

RESULTS

Substantial variation between methods was demonstrated in volunteers. In simulations the dual-bolus method proved stable for realistic levels of saturation efficiency but demonstrated bias due to residual nonlinearity. Model-based methods performed ideally in the absence of confounding error sources and were generally robust to noise or saturation imperfection, except for native T1 based correction which was highly sensitive to the latter. All methods demonstrated large variation in accuracy above an over-saturation level where baseline signal was nulled. For the dual-sequence approach this caused substantial bias at the saturation efficiencies observed in volunteers.

CONCLUSION

The choice of nonlinearity correction method in myocardial DCE-MRI impacts on accuracy and precision of estimated parameters, particularly in the presence of nonideal saturation.

Cell therapy in reperfused acute myocardial infarction does not improve the recovery of perfusion in the infarcted myocardium: a cardiac MR imaging study

PURPOSE

To investigate the effects of cell therapy on myocardial perfusion recovery after treatment of acute myocardial infarction (MI) with primary percutaneous coronary intervention (PCI).

MATERIALS AND METHODS

In this HEBE trial substudy, which was approved by the institutional review board (trial registry number ISRCTN95796863), the authors assessed the effects of intracoronary infusion with bone marrow-derived mononuclear cells (BMMCs) or peripheral blood-derived mononuclear cells (PBMCs) on myocardial perfusion recovery by using cardiac magnetic resonance (MR) imaging after revascularization. In 152 patients with acute MI treated with PCI, cardiac MR imaging was performed after obtaining informed consent-before randomization to BMMC, PBMC, or standard therapy (control group)-and repeated at 4-month follow-up. Cardiac MR imaging consisted of cine, rest first-pass perfusion, and late gadolinium enhancement imaging. Perfusion was evaluated semiquantitatively with signal intensity-time curves by calculating the relative upslope (percentage signal intensity change). The relative upslope was calculated for the MI core, adjacent border zone, and remote myocardium. Perfusion differences among treatment groups or between baseline and follow-up were assessed with the Wilcoxon signed rank or Mann-Whitney U test.

RESULTS

At baseline, myocardial perfusion differed between the MI core (median, 6.0%; interquartile range [IQR], 4.1%-8.0%), border zone (median, 8.4%; IQR, 6.4%-10.2%), and remote myocardium (median, 12.2%; IQR, 10.5%-15.9%) (P < .001 for all), with equal distribution among treatment groups. These interregional differences persisted at follow-up (P < .001 for all). No difference in perfusion recovery was found between the three treatment groups for any region.

CONCLUSION

After revascularization of ST-elevation MI, cell therapy does not augment the recovery of resting perfusion in either the MI core or border zone.