Partial Right Atrial Inflow Occlusion for Transient Systemic Hypotension During Deployment of Thoracic Stentgrafts.

PURPOSE: Temporary balloon occlusion of the inferior vena cava to lower cardiac output is a relatively infrequently used technique to induce controlled systemic hypotension. In this technical note, we describe the feasibility, reliability, and safety of partial occlusion of right atrial inflow and the effect on systemic blood pressure during the deployment of a thoracic stentgraft. MATERIALS AND METHODS: Twenty consecutive patients undergoing thoracic endovascular aortic repair, with proximal landing in zone 0-3 of the thoracic aorta, were prospectively included. Right atrial inflow occlusion was performed with a compliant occlusion balloon. RESULTS: Median time to reach a mean arterial pressure of 50 mmHg was 43 s. Median recovery time of blood pressure was 42 s. CONCLUSION: Partial right atrial inflow occlusion with an occlusion balloon is feasible with reliable results and without procedure-related complications.

Assessing heterogeneous distribution of blood flow and metabolism in the heart.

The literature is reviewed on methods to assess heterogeneity of blood flow, substrate uptake and oxidative end energy metabolism in the normal heart, and their interrelations. Even though the factors controlling matching on the regional level remain largely obscure, the evidence that heterogeneous blood flow partially correlates to indicators of metabolism in the normal heart is accumulating, particularly in face of a correlation between acetate metabolism indicative of regional O2 consumption to microsphere blood flow. Moreover, the partial matching cannot be explained by vascular anatomical differences from one region to the other, since, although fractal theory can partially describe the branching patterns of the coronaries, vasodilation is similar among regions upon metabolic stimulation of the heart. It is dissimilar among regions, so that blood flow is redistributed, upon maximum vasodilation with adenosine or hypoxia, denoting regionally different maximum vessel diameter and flow reserve. However, regionally differing tissue composition could also contribute somewhat to regional differences in (the need for) blood flow. It is still unknown, because of technical limitations, how the foregoing measures relate to regional work load.

A (13)C NMR double-labeling method to quantitate local myocardial O(2) consumption using frozen tissue samples.

Measurement of local myocardial O(2) consumption (VO(2)) has been problematic but is needed to investigate the heterogeneity of aerobic metabolism. The goal of the present investigation was to develop a method to measure local VO(2) using small frozen myocardial samples, suitable for determining VO(2) profiles. In 26 isolated rabbit hearts, 1.5 mmol/l [2-(13)C]acetate was infused for 4 min, followed by 1.5 min of [1,2-(13)C]acetate. The left ventricular (LV) free wall was then quickly frozen. High-resolution (13)C-NMR spectra were measured from extracts taken from 2- to 3-mm thick transmural layer samples. The multiplet intensities of glutamate were analyzed with a computer model allowing simultaneous estimation of the absolute flux through the tricarboxylic acid cycle and the fractional contribution of acetate to acetyl CoA formation from which local VO(2) was calculated. The (13)C-derived VO(2) in the LV free wall was linearly related to "gold standard" VO(2) from coronary venous O(2) electrode measurements in the same region (r = 0.932, n = 22, P < 0.0001, slope 1.05) for control and lowered metabolic rates. The ratio of subendocardial to subepicardial VO(2) was 1.52 +/- 0.19 (SE, significantly >1, P < 0.025). Local myocardial VO(2) can now be quantitated with this new (13)C method to determine profiles of aerobic energy metabolism.