1H- and 31P-myocardial magnetic resonance spectroscopy in non-obstructive hypertrophic cardiomyopathy patients and competitive athletes

In Vivo Magnetic Resonance Spectroscopy Methods for Investigating Cardiac Metabolism

Magnetic resonance spectroscopy (MRS) is a non-invasive and non-ionizing technique, enabling in vivo investigation of cardiac metabolism in normal and diseased hearts. In vivo measurement tools are critical for studying mechanisms that regulate cardiac energy metabolism in disease developments and to assist in early response assessments to novel therapies. For cardiac MRS, proton (1H), phosphorus (31P), and hyperpolarized 13-carbon (13C) provide valuable metabolic information for diagnosis and treatment assessment purposes. Currently, low sensitivity and some technical limitations limit the utility of MRS. An essential step in translating MRS for clinical use involves further technological improvements, particularly in coil design, improving the signal-to-noise ratios, field homogeneity, and optimizing radiofrequency sequences. This review addresses the recent advances in metabolic imaging by MRS from primarily the literature published since 2015.

Heart of the World's Top Ultramarathon Runner-Not Necessarily Much Different from Normal

The impact of ultramarathon (UM) runs on the organs of competitors, especially elite individuals, is poorly understood. We tested a 36-year-old UM runner before, 1–2 days after, and 10–11 days after winning a 24-h UM as a part of the Polish Championships (258.228 km). During each testing session, we performed an electrocardiogram (ECG), transthoracic echocardiography (TTE), cardiac magnetic resonance imaging (MRI), cardiac ³¹P magnetic resonance spectroscopy (³¹P MRS), and blood tests. Initially, increased cholesterol and low-density lipoprotein cholesterol (LDL-C) levels were identified. The day after the UM, increased levels of white blood cells, neutrophils, fibrinogen, alanine aminotransferase, aspartate aminotransferase, creatine kinase, C-reactive protein, and N-terminal type B natriuretic propeptide were observed. Additionally, decreases in hemoglobin, hematocrit, cholesterol, LDL-C, and hyponatremia were observed. On day 10, all measurements returned to normal levels, and cholesterol and LDL-C returned to their baseline abnormal values. ECG, TTE, MRI, and ³¹P MRS remained within the normal ranges, demonstrating physiological adaptation to exercise. The transient changes in laboratory test results were typical for the extreme efforts of the athlete and most likely reflected transient but massive striated muscle damage, liver cell damage, activation of inflammatory processes, effects on the coagulation system, exercise-associated hyponatremia, and cytoprotective or growth-regulatory effects. These results indicated that many years of intensive endurance training and numerous UMs (including the last 24-h UM) did not have a permanent adverse effect on this world-class UM runner’s body and heart. Transient post-competition anomalies in laboratory test results were typical of those commonly observed after UM efforts.

Myocardial triglycerides in cardiac amyloidosis assessed by proton cardiovascular magnetic resonance spectroscopy

BACKGROUND

Cardiac involvement of amyloidosis leads to left-ventricular (LV) wall thickening with progressive heart failure requiring rehospitalization. Cardiovascular magnetic resonance (CMR) is a valuable tool to non-invasively assess myocardial thickening as well as structural changes. Proton CMR spectroscopy (1H-CMRS) additionally allows assessing metabolites including triglycerides (TG) and total creatine (CR). However, opposing results exist regarding utilization of these metabolites in LV hypertrophy or thickening. Therefore, the aim of this study was to measure metabolic alterations using 1H-CMRS in a group of patients with thickened myocardium caused by cardiac amyloidosis.

METHODS

1H-CMRS was performed on a 1.5 T system (Achieva, Philips Healthcare, Best, The Netherlands) using a 5-channel receive coil in 11 patients with cardiac amyloidosis (60.5 ± 11.4 years, 8 males) and 11 age- and gender-matched controls (63.2 ± 8.9 years, 8 males). After cardiac morphology and function assessment, proton spectra from the interventricular septum (IVS) were acquired using a double-triggered PRESS sequence. Post-processing was performed using a customized reconstruction pipeline based on ReconFrame (GyroTools LLC, Zurich, Switzerland). Spectra were fitted in jMRUI/AMARES and the ratios of triglyceride-to-water (TG/W) and total creatine-to-water (CR/W) were calculated.

RESULTS

Besides an increased LV mass and a thickened IVS concomitant to the disease characteristics, patients with cardiac amyloidosis presented with decreased global longitudinal (GLS) and circumferential (GCS) strain. LV ejection fraction was preserved relative to controls (60.0 ± 13.2 vs. 66.1 ± 4.3%, p = 0.17). Myocardial TG/W ratios were significantly decreased compared to controls (0.53 ± 0.23 vs. 0.80 ± 0.26%, p = 0.015). CR/W ratios did not show a difference between both groups, but a higher standard deviation in patients with cardiac amyloidosis was observed. Pearson correlation revealed a negative association between elevated LV mass and TG/W (R = - 0.59, p = 0.004) as well as GCS (R = - 0.48, p = 0.025).

CONCLUSIONS

A decrease in myocardial TG/W can be detected in patients with cardiac amyloidosis alongside impaired cardiac function with an association to the degree of myocardial thickening. Accordingly, 1H-CMRS may provide an additional diagnostic tool to gauge progression of cardiac amyloidosis along with standard imaging sequences.

TRIAL REGISTRATION

EK 2013-0132.