Prognostic Value of Hyperpolarized 13C MRI for Clinical Myocardial Viability

University of Texas Southwestern Medical Center30 enrolled

Overview

Heart failure due to coronary artery disease represents a significant cause of mortality. The detection of patients eligible for bypass surgery is a pivotal concern. Nevertheless, the optimal approach for patient selection based on conventional imaging scans remains unclear. The proposed method (Hyperpolarized 13C MRI) has gained extensive use in evaluating in vivo metabolism. This method avoids ionizing radiation and provides critical insights into cardiac function. The feasibility study aims to investigate this method for patient selection before bypass surgery. This innovative imaging technique facilitates the identification of two simple molecules, bicarbonate and lactic acid, produced at high rates by normal heart metabolism. Both bicarbonate and lactate originate from the same precursor molecule, pyruvate. The data generated from this study holds the potential to refine diagnostic precision.

PRIMARY OBJECTIVES: The principal aim of this investigation is to employ noninvasive techniques for the in vivo assessment of segmental myocardial metabolism. This will be achieved by measuring the hyperpolarized (HP) 13C bicarbonate-to-lactate (bic/lac) ratio in patients scheduled for coronary artery bypass surgery (CABG), both preoperatively and 4-6 months postoperatively. These findings will be compared with a control group of healthy subjects to establish normal metabolic values. SECONDARY OBJECTIVES: In addition to the primary objectives, this study seeks to accomplish the following secondary objectives: 1. To ascertain the safety profile and tolerability of HP \[1-13C\] pyruvate administration during the MRI exam. 2. To evaluate the reproducibility of the HP 13C MRI data if the optional second injection of hyperpolarized 13C pyruvate is administered. EXPLORATORY OBJECTIVES: In pursuit of further insights, this research also aims to explore the following: 1. Investigate potential associations between blood measurements for pyruvate, triglycerides, free fatty acids, and insulin levels with the bicarbonate/lactate ratio within the myocardium. 2. Explore correlations between segmental myocardial metabolism (the bic/lac ratio) and mechanical function, such as echocardiographic measurements of wall motion.

Study Type

OBSERVATIONAL

Enrollment

Conditions

Eligibility

Sex: ALLMin age: 20 YearsMax age: 80 YearsHealthy volunteers:

Medical Language ↔ Plain English

The eligibility criteria for this feasibility study are designed to select participants who will provide valuable insights into myocardial metabolism using HP-13C MRI in various contexts related to ischemic heart failure. These criteria aim to ensure that the study population is diverse and representative of the patient groups under investigation. Inclusion/Exclusion Criteria: * Age range: 20 to 80 years * Sex: Random allocation * Left ventricular ejection fraction (LVEF): * Preoperative patients with LVEF \< 0.35 * Healthy subjects with LVEF \> 0.50 * Clinical history: * Previous myocardial infarction (MI): Excluded for healthy subjects, included for preoperative patients. * Diabetes mellitus: Excluded for all participants. * Hypertension: Included for all participants * Mean blood pressure: Systolic \< 140 mm Hg and Diastolic \< 90 mm Hg for all participants * Mean heart rate: 78 beats/min for all participants * Current smoker status: Included but will be reported. * Medication use within 24 hours: Use will be reported. * Coronary artery bypass surgery history: Excluded for healthy subjects, included for preoperative patients. * Infarct type and location: Excluded for healthy subjects, included for preoperative patients with various Q-wave infarct types and locations. * Number of diseased coronary vessels: Excluded for healthy subjects, included for preoperative patients with at least one diseased vessel. * Additional medical history and clinical data: Variations in data availability are expected based on the practices of referring physicians and will be documented.

Outcomes

Primary Outcomes

Bicarbonate-to-Lactate Ratio in Healthy Control Subjects

Assessment of normal segmental myocardial metabolism by measuring the ratio of hyperpolarized (HP) \[13C\]-bicarbonate to HP \[1-13C\]lactate (bic/lac ratio). This is obtained during an HP-13C MRI utilizing \[1-13C\] pyruvate to establish baseline normal values for healthy subjects.

Time frame: Baseline (Day 1 of imaging)

Bicarbonate-to-Lactate Ratio in Preoperative CAD Patients

Assessment of segmental myocardial metabolism and mechanical function in patients scheduled for coronary artery bypass surgery. The bic/lac ratio is measured using HP-13C MRI to identify abnormal cardiac metabolism and impaired oxidative function. These metabolic findings will be correlated with echocardiographic measurements of wall motion and viability studies obtained by the referring cardiologist.

Time frame: Preoperative imaging day

Change in Bicarbonate-to-Lactate Ratio Post-Surgery

Follow-up assessment of segmental myocardial metabolism to evaluate the remodeling of cardiac metabolism as a consequence of surgery. The bic/lac ratio is measured using HP-13C MRI to determine if the ratio has increased compared to the patient's preoperative baseline, indicating improved oxidative function.

Time frame: 4-6 months after surgical coronary revascularization