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Effects of substrate availability on myocardial C-11 palmitate kinetics by positron emission tomography in normal subjects and patients with ventricular dysfunction.

Abstract：

:The possibility of demonstrating noninvasively with C-11 palmitate and positron emission tomography (PET) changes in myocardial substrate metabolism in normal and diseased human myocardium in response to altered substrate availability in blood and disease-related abnormalities was examined in five normal volunteers and 16 patients with ventricular dysfunction. C-11 palmitate injection and serial PET imaging were performed after an overnight fast (control period) and again 2 hours later after oral glucose (50 gm). Myocardial C-11 time-activity curves from serial PET images revealed a biexponential clearance pattern. An early rapid phase, defined by relative size and clearance half-time, reflects C-11 palmitate oxidation and the late slow phase tracer deposition in the endogenous lipid pool. During the control period, the tracer fraction entering the early rapid phase averaged 47 +/- 13% (SD) in normal subjects and 45 +/- 12% in patients. Corresponding clearance half-times were 19 +/- 7 and 20 +/- 5 minutes, respectively. Heart rate and blood pressure remained unchanged after glucose, but plasma glucose levels rose by 72.5% in normal subjects and by 98.9% in patients, while free fatty acid levels fell by 72% and 42% (p less than 0.001), respectively. In normal subjects, the tracer fraction in the early rapid phase fell by 43% (p less than 0.005) and the clearance half-time increased by 46% (p less than 0.01). In patients, the response of C-11 palmitate tissue kinetics to glucose was variable. In nine patients, it was similar to that in normal subjects while in the other seven patients a "paradoxic" response occurred. The tracer fraction entering the rapid clearance phase increased after glucose by 30% (p less than 0.05) associated with a 36% (p less than 0.05) decline in clearance half-times. The paradoxic response was unrelated to disease etiology or plasma substrate levels but occurred mostly in left ventricles with more severely depressed function. Thus, PET and C-11 palmitate allow the noninvasive demonstration of the known response of substrate metabolism of the human heart to altered substrate availability. Glucose administration in fasted humans serves as a provocative test of substrate regulation which can be abnormal in myocardial disease and can be demonstrated noninvasively.

journal_name

Am Heart J

journal_title

American heart journal

authors

Schelbert HR,Henze E,Sochor H,Grossman RG,Huang SC,Barrio JR,Schwaiger M,Phelps ME

doi

10.1016/0002-8703(86)90006-2

subject

Has Abstract

pub_date

1986-06-01 00:00:00

pages

1055-64

issue

eissn

0002-8703

issn

1097-6744

pii

0002-8703(86)90006-2

journal_volume

111

pub_type

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Effects of substrate availability on myocardial C-11 palmitate kinetics by positron emission tomography in normal subjects and patients with ventricular dysfunction.