Complications of exercise and pharmacologic stress echocardiography.

Stress echocardiography is a diagnostic cardiovascular exam that is commonly utilized for multiple indications, including but not limited to the assessment of obstructive coronary artery disease, valvular disease, obstructive hypertrophic cardiomyopathy, and diastolic function. Stress echocardiography can be performed via both exercise and pharmacologic modalities. Exercise stress is performed with either treadmill or bicycle-based exercise. Pharmacologic stress is performed via either dobutamine or vasodilator-mediated (i.e., dipyridamole, adenosine) stress testing. Each of these modalities is associated with a low overall prevalence of major, life-threatening adverse outcomes, though adverse events are most common with dobutamine stress echocardiography. In light of the recent COVID-19 pandemic, the risk of infectious complications to both the patient and stress personnel cannot be negated; however, when certain precautions are taken, the risk of infectious complications appears minimal. In this article, we review each of the stress echocardiographic modalities, examine major potential adverse outcomes and contraindications, assess the risks of stress testing in the setting of a global pandemic, and examine the utilization and safety of stress testing in special patient populations (i.e., language barriers, pediatric patients, pregnancy).

Distinct Effects of Left or Right Atrial Cannulation on Left Ventricular Hemodynamics in a Swine Model of Acute Myocardial Injury.

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) and the TandemHeart left ventricular (LV) assist device are increasingly employed as mechanical circulatory support devices during acute LV injury. We examined the effects of right atrial to femoral artery (RA-FA; VA-ECMO) bypass versus left atrial to femoral artery (LA-FA; TandemHeart) bypass using a centrifugal pump (Cardiac Assist Inc, Pittsburgh, PA) on LV hemodynamics in a swine model of acute LV injury. In eight male swine, the RA-FA bypass group employed a 21 Fr inflow cannula in the right atrial (RA) and a 17 Fr FA outflow cannula. The LA-FA bypass group employed a 21 Fr inflow cannula in the LA and a 17 Fr FA outflow cannula. Both pump configurations were activated at 3,500 rotations per minute (RPMs) followed by balloon angioplasty-mediated occlusion of the left circumflex (LCx) artery. After 30 minutes of LCx occlusion, RPMs through the centrifugal pump were increased from 3,500, 5,500 then to a maximum at 7,500 RPMs. At 7,500 RPMs, RA-FA and LA-FA bypass generated 3.5 ± 0.1 and 3.6 ± 0.2 liters/minute (LPM) of flow, respectively. At maximum flow, RA unloading increased LV end-systolic pressure and estimated wall stress, whereas LA unloading reduced LV end-diastolic pressure, end-diastolic volume, and native stroke volume without changing estimated wall stress. Veno-arterial extracorporeal membrane oxygenation acutely increases mean arterial pressure (MAP) without unloading the LV, whereas the TandemHeart maintains MAP and unloads the LV. These findings indicate that RA versus LA cannulation for circulatory support have distinct acute hemodynamic effects on the LV.

Mechanical Pre-Conditioning With Acute Circulatory Support Before Reperfusion Limits Infarct Size in Acute Myocardial Infarction.

OBJECTIVES: This study tested the hypothesis that first reducing myocardial work by unloading the left ventricle (LV) with a novel intracorporeal axial flow catheter while delaying coronary reperfusion activates a myocardial protection program and reduces infarct size. BACKGROUND: Ischemic heart disease is a major cause of morbidity and mortality worldwide. Primary myocardial reperfusion remains the gold standard for the treatment of an acute myocardial infarction (AMI); however, ischemia-reperfusion injury contributes to residual myocardial damage and subsequent heart failure. Stromal cell-derived factor (SDF)-1α is a chemokine that activates cardioprotective signaling via Akt, extracellular regulated kinase, and glycogen synthase kinase-3ß. METHODS: AMI was induced by occlusion of the left anterior descending artery (LAD) via angioplasty for 90 min in 50-kg male Yorkshire swine (n = 5/group). In the primary reperfusion (1° Reperfusion) group, the LAD was reperfused for 120 min. In the primary unloading (1° Unloading) group, after 90 min of ischemia the axial flow pump was activated and the LAD left occluded for an additional 60 min, followed by 120 min of reperfusion. Myocardial infarct size and kinase activity were quantified. RESULTS: Compared with 1° Reperfusion, 1° Unloading reduced LV wall stress and increased myocardial levels of SDF-1α, CXCR4, and phosphorylated Akt, extracellular regulated kinase, and glycogen synthase kinase-3ß in the infarct zone. 1° Unloading increased antiapoptotic signaling and reduced myocardial infarct size by 43% compared with 1° Reperfusion (73 ± 13% vs. 42 ± 8%; p = 0.005). Myocardial levels of SDF-1 correlated inversely with infarct size (R = 0.89; p < 0.01). CONCLUSIONS: Compared with the contemporary strategy of primary reperfusion, mechanically conditioning the myocardium using a novel axial flow catheter while delaying coronary reperfusion decreases LV wall stress and activates a myocardial protection program that up-regulates SDF-1α/CXCR4 expression, increases cardioprotective signaling, reduces apoptosis, and limits myocardial damage in AMI.