Evaluation of Cardiac Mitochondrial Function by a Nuclear Imaging Technique using Technetium-99m-MIBI Uptake Kinetics

Abstract

Mitochondria play an important role in energy production for the cell. The proper function of a myocardial cell largely depends on the functional capacity of the mitochondria. Therefore it is necessary to establish a novel and reliable method for a non-invasive assessment of mitochondrial function and metabolism in humans. Although originally designed for evaluating myocardial perfusion, (99m)Tc-MIBI can be also used to evaluate cardiac mitochondrial function. In a clinical study on ischemic heart disease, reverse redistribution of (99m)Tc-MIBI was evident after direct percutaneous transluminal coronary angioplasty. The presence of increased washout of (99m)Tc-MIBI was associated with the infarct-related artery and preserved left ventricular function. In non-ischemic cardiomyopathy, an increased washout rate of (99m)Tc-MIBI, which correlated inversely with left ventricular ejection fraction, was observed in patients with congestive heart failure. Increased (99m)Tc-MIBI washout was also observed in mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and in doxorubicin-induced cardiomyopathy. Noninvasive assessment of cardiac mitochondrial function could be greatly beneficial in monitoring possible cardiotoxic drug use and in the evaluation of cardiac damage in clinical medicine.

Keywords: 99mTc-MIBI; cardiomyopathy; heart failure; ischemic heart disease; mitochondria.

Figure 1

Kinetics of ^99mTc-MIBI in the cell. ^99mTc-MIBI accumulates and concentrates into cell according to membrane potential

Figure 2

Quantitative analysis by heart-to-mediastinum count ratio on planar image. M = mediastinum; H = heart.

Figure 3

Quantitative gated-SPECT provides cardiac systolic and diastolic functional information. The cardiac function deteriorated in a patient after chemotherapy.

Figure 4

Initial and delayed planar images after administration of ^99mTc-MIBI, on baseline and after chemotherapy in a female patient (37 y.o.) with osteosarcoma. The washout rate is increased after chemotherapy (21% on baseline to 30% after chemotherapy).