Fasting and postprandial ischemic threshold in patients with unstable angina with and without postprandial angina at rest

Absence of postprandial surge in coronary blood flow distal to significant stenosis: a possible mechanism of postprandial angina

OBJECTIVES

This study was designed to investigate a possible mechanism of postprandial angina.

BACKGROUND

Postprandial angina has been recognized for more than two centuries; however, its mechanism is still controversial. The most widely accepted mechanism involves increased myocardial oxygen demand after food intake. Recently, the redistribution in coronary blood flow (CBF) was suggested as a possible mechanism.

METHODS

Twenty young, healthy volunteer controls and 20 patients with significant stenosis in the left anterior descending (LAD) or left main coronary artery were enrolled in the study. Coronary blood flow was evaluated in the distal LAD by using transthoracic Doppler echocardiography before and 15, 30, 45, and 60 min after food intake. In the CBF curve, the time velocity integral of diastolic flow (Dtvi) and the product of Dtvi and heart rate (HR) were measured. In six patients, these measurements were repeated after successful coronary intervention.

RESULTS

In the healthy volunteer controls, Dtvi and Dtvi x HR increased after food intake with a peak value at 15 min, which indicates the presence of postprandial surge in the CBF. Fasting values and peak values at 15 min were significantly different (Dtvi: 15.1 +/- 4.9 cm/s vs. 18.9 +/- 5.9 cm/s, p = 0.04, Dtvi x HR: 862.2 +/- 261.5 cm/min vs. 1,174.2 +/- 307.5, p = 0.002). In contrast with the controls, despite postprandial increase in double product (HR x blood pressure), Dtvi and Dtvi x HR in the patient group decreased after food intake, with a nadir value at 45 min. Fasting values and nadir values at 45 min were significantly different (Dtvi: 24.0 +/- 19.6 cm/s vs. 19.3 +/- 17.1 cm/s, p < 0.001, Dtvi x HR: 1,449.6 +/- 1,044.0 cm/min vs. 1,273.4 +/- 1,000.9 cm/min, p = 0.002). In six patients, the CBF pattern resumed the normal pattern of postprandial surge in the CBF after successful coronary intervention.

CONCLUSIONS

Results of our study suggest that "steal phenomenon" may play a role in the mechanism of postprandial angina.

Fibrinogen-coated chylomicrons in gastrointestinal lymph: a new rationale regarding the arterial deposition of postprandial lipids

The recent discovery that fibrinogen binds to chylomicrons in gastrointestinal lymph has prompted a new rationale regarding the arterial deposition of postprandial lipids, i.e., dietary fat. According to this new rationale, fibrinogen bound to chylomicrons in the gastrointestinal lymph renders those lipid particles and/or their remnants an adhesive potential, even before the particles reach the arterial system. It is proposed that such an adhesive potential, if realized in the vicinity of the arterial wall, can contribute to the nucleation and growth of atherosclerotic plaques, especially during and immediately following a fat-rich meal. Arguments in support of this proposal are made based on the proximity of the lymph outflow tract to the arteries most susceptible to atherosclerosis, and on the tissue distributions and activities of heparin, diamine oxidase, and lipoprotein lipase. This new rationale reconciles existing theories on atherosclerosis, and it also suggests novel means by which to prevent/treat the disease.