Detection of moderate regional ischemia in pig hearts in vivo by near-infrared and thermal imaging: effects of dipyridamole

Percutaneous cardiac support during myocardial infarction drastically reduces mortality: perspectives from a swine model

BACKGROUND/AIMS

Acute myocardial infarction (AMI) with cardiogenic shock (CS) remains the leading cause of in-hospital death in acute coronary syndromes. In the AMI-CS pig model we tested the efficacy of temporary percutaneous cardiorespiratory assist device (PCRA) in rescuing the failing heart and reducing early mortality.

METHODS

In open-chest pigs we induced AMI by proximal left anterior descending coronary artery (LAD) ligation. Eight animals without PCRA (C group) were compared with 12 animals otherwise treated with PCRA (T group), starting approximately at 60 minutes post-occlusion and lasting 120-180 minutes. In 3 animals of the T group, regional myocardial oxygen content was also imaged by two-dimensional near infrared spectroscopy (2D-NIRS) with and without PCRA, before and after LAD reperfusion.

RESULTS

All animals without PCRA died despite unrelenting resuscitation maneuvers (120 minutes average survival time). Conversely, animals treated with PCRA showed a reduction in life-threatening arrhythmia and maintenance of aortic pressure, allowing interruption of PCRA in all cases early in the experiments, with sound hemodynamics at the end of the observation period. During LAD occlusion, NIRS showed severe de-oxygenation of the LAD territory that improved with PCRA. After PCRA suspension and LAD reperfusion, the residual de-oxygenated area proved to be smaller than the initial risk area.

CONCLUSIONS

In AMI, PCRA initiated during advanced CS drastically reduced early mortality from 100% to 0% in a 4-5 hour observation period. PCRA promoted oxygenation of the ischemic area during LAD occlusion. Results support the use of PCRA as first line of treatment in AMI-CS, improving myocardial rescue and short-term survival.

NIR spectroscopic imaging to map hemoglobin + myoglobin oxygenation, their concentration and optical pathlength across a beating pig heart during surgery

The purpose of this paper is to demonstrate that near-infrared (NIR) spectroscopic imaging can provide spatial distribution (maps) of the absolute concentration of hemoglobin + myoglobin, oxygen saturation parameter and optical pathlength, reporting on the biochemico-physiological status of a beating heart in vivo. The method is based on processing the NIR spectroscopic images employing a first-derivative approach. Blood-pressure-controlled gating compensated the effect of heart motion on the imaging. All the maps are available simultaneously and noninvasively at a spatial resolution in the submillimeter range and can be obtained in a couple of minutes. The equipment has no mechanical contact with the tissue, thereby leaving the heart unaffected during the measurement.

Visualization and grading of regional ischemia in pigs in vivo using near-infrared and thermal imagingThis paper is one of a selection of papers published in this Special Issue, entitled The Cellular and Molecular Basis of Cardiovascular Dysfunction, Dhalla 70th Birthday Tribute

Reductions in regional coronary flow result in tissue deoxygenation and decrease in surface temperature, changes detectable by near-infrared spectroscopic (NIRS) and thermal imaging, respectively. In anesthetized open-chest pigs, an inflatable occluder and flow probe were placed around the left anterior descending artery. Gated NIRS and nongated thermal images were acquired at baseline, partial (17% and 50%), and complete occlusion and reflow. At each step, dobutamine was infused (10 μg·min–1·kg–1) for 7–9 min to increase blood pressure and flow. Changes in the oxygen saturation parameter, rate of indocyanine green flow tracer passage, and the surface temperature were correlated with the measured left anterior descending artery flow. Location and sizes of the areas of reduced oxygenation, indocyanine green uptake, and temperature were similar. Decrease in the coronary flow to 50% and 17% of baseline resulted in progressive decrease in the above parameters, whereas increase in flow from 75% to ~250% achieved by dobutamine and reactive hyperemia did not significantly change them. Dobutamine increased total and epicardial flow in ischemic areas and increased subepicardial oxygenation. NIRS and thermal imaging provide epicardial maps of oxygen saturation and perfusion that reveal ischemic areas. Combination of these techniques may be useful in the coronary artery bypass graft (CABG) surgery setting.