Detection of remote myocardial infarction in patients with positron emission transaxial tomography and intravenous 11C-palmitate.

Abstract

Ischemic myocardial injury has been detected recently in isolated perfused hearts and intact experimental animals with positron-emitting 11C-palmitate and reconstructive tomography providing cross-sectional images of the heart free from superimposed activity in overlying structures. To evaluate the applicability of positron emission transaxial tomography in detecting infarction in man, 10 normal human subjects and 12 patients who sustained documented acute myocardial infarction three to 12 months previously were studied. Tomograms were obtained after intravenous injection of 5 to 10 mCi of 11C-labeled palmitate, a physiological substrate of myocardium. Tomograms from all normal subjects exhibited homogeneous distribution of 11C-palmitate throughout each 1.5 cm thick cross section of the ventricle. Tomograms from all patients with remote anterior or inferior and posterior myocardial infarction exhibited diminished accumulation of 11C-palmitate delineating regions corresponding to the electrocardiographic locus of infarction. The distribution of 11C-palmitate detectable by positron emission transaxial tomography in a series of cross sections from apex to base in the same normal subject or patient with remote myocardial infarction was analogous to that observed in normal dogs and animals with experimentally induced myocardial infarction.

Regional assessment of myocardial metabolic integrity in vivo by positron-emission tomography with 11C-labeled palmitate.

“…A substantial portion is incorporated into triglycerides, before subsequent lipolysis and oxidation. 23 Hydrolysis of triglycerides to liberate fatty acid from temporary intracellular storage is accelerated during conditions of increased energy requirements.38 Some of the extracted and thioesterified fatty acid is transported into mitochondria via a system of chain-length-specific carnitine transferases, where it undergoes beta-oxidation with production of acetyl-CoA, ultimately oxidized to C02. 3' Because of the complex interrelationships of factors influencing the uptake, accumulation and egress of "C-counts from the heart exposed to "C-labeled fatty acid in vivo, we recently evaluated isolated perfused hearts under conditions of constant flow and imposed alterations in oxidation requirements induced by inflation of an intraventricular balloon and monitored by indexes such as tension-time index and peak dP/dt.…”

External quantification of myocardial perfusion by exponential infusion of positron-emitting radionuclides.

“…Regional myocardial mass and, by calculation, flow/mass, can be determined from definition of pixel size and depth. We have shown that the resolution of the PET instrument is sufficient to permit quantification of the regional distribution of tracer within hearts of patients during imaging, and that regional tissue mass can be determined accurately and reproducibly by knowing pixel size and depth (19)(20)(21) …”

Estimation of myocardial infarct size with ultrasonic tissue characterization.

“…Adult mongrel dogs of either sex weighing [15][16][17][18][19][20][21][22][23][24][25] the left fifth intercostal space. The lung was retracted and the heart suspended in a pericardial cradle.…”