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Acute Left Ventricular Unloading Reduces Atrial Stretch and Inhibits Atrial Arrhythmias.

ABSTRACT: BACKGROUND:Left atrium (LA) physiology is influenced by changes in left ventricular (LV) performance and load. OBJECTIVES:The purpose of this study was to define the effect of acute changes in LV loading conditions on LA physiology in subacute myocardial infarction (MI). METHODS:MI was percutaneously induced in 19 Yorkshire pigs. One to 2 weeks after MI, 14 pigs underwent acute LV unloading using a percutaneous LV assist device, Impella. The remaining 5 pigs underwent acute LV loading by percutaneous induction of aortic regurgitation. A pressure-volume catheter was inserted into the LA using a percutaneous transseptal approach, and LA pressure-volume loops were continuously monitored. Atrial arrhythmia inducibility was examined by burst-pacing of the right atrium. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) levels and ryanodine receptor phosphorylation were examined in LA tissues to study the potential effect of stretch-dependent oxidative stress. RESULTS:MI resulted in reduced LV ejection fraction and increased LV end-diastolic pressure with concomitant increase in LA pressure and volumes. Acute LV unloading resulted in a reduction of LV end-diastolic pressure, which led to proportional decreases in mean LA pressure and maximum LA volume. LA pressure-volume loops exhibited a pump flow-dependent, left-downward shift. This was associated with reduced LA passive stiffness, suggesting the alleviation of the LA stretch that was present after MI. Prior to acute unloading of the LV, 71% of the pigs were arrhythmia-inducible; LV unloading reduced this to 29% (p = 0.02). Time to spontaneous termination of atrial arrhythmias was decreased from median 55 s (range 5 to 300 s) to 3 s (range 0 to 59 s). In contrast, acute LV loading with aortic regurgitation increased LA pressure without a significant effect on arrhythmogenicity. Molecular analysis of LA tissue revealed that NOX2 expression was increased after MI, whereas acute LV unloading reduced NOX2 levels and diminished ryanodine receptor phosphorylation. CONCLUSIONS:Acute LV unloading relieves LA stretch and reduces atrial arrhythmogenicity in subacute MI.

SUBMITTER: Ishikawa K

PROVIDER: S-EPMC6160394 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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Acute Left Ventricular Unloading Reduces Atrial Stretch and Inhibits Atrial Arrhythmias.

Ishikawa Kiyotake K Watanabe Shin S Lee Philyoung P Akar Fadi G FG Lee Ahyoung A Bikou Olympia O Fish Kenneth K Kho Changwon C Hajjar Roger J RJ

Journal of the American College of Cardiology 20180801 7

<h4>Background</h4>Left atrium (LA) physiology is influenced by changes in left ventricular (LV) performance and load.<h4>Objectives</h4>The purpose of this study was to define the effect of acute changes in LV loading conditions on LA physiology in subacute myocardial infarction (MI).<h4>Methods</h4>MI was percutaneously induced in 19 Yorkshire pigs. One to 2 weeks after MI, 14 pigs underwent acute LV unloading using a percutaneous LV assist device, Impella. The remaining 5 pigs underwent acute ...[more]

PMID: 30092950

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Project description:BACKGROUND:Heart failure after an acute myocardial infarction (AMI) is a major cause of morbidity and mortality worldwide. We recently reported that activation of a transvalvular axial-flow pump in the left ventricle and delaying myocardial reperfusion, known as primary unloading, limits infarct size after AMI. The mechanisms underlying the cardioprotective benefit of primary unloading and whether the acute decrease in infarct size results in a durable reduction in LV scar and improves cardiac function remain unknown. OBJECTIVES:This study tested the importance of LV unloading before reperfusion, explored cardioprotective mechanisms, and determined the late-term impact of primary unloading on myocardial function. METHODS:Adult male swine were subjected to primary reperfusion or primary unloading after 90 min of percutaneous left anterior descending artery occlusion. RESULTS:Compared with primary reperfusion, 30 min of LV unloading was necessary and sufficient before reperfusion to limit infarct size 28 days after AMI. Compared with primary reperfusion, primary unloading increased expression of genes associated with cellular respiration and mitochondrial integrity within the infarct zone. Primary unloading for 30 min further reduced activity levels of proteases known to degrade the cardioprotective cytokine, stromal-derived factor (SDF)-1?, thereby increasing SDF-1? signaling via reperfusion injury salvage kinases, which limits apoptosis within the infarct zone. Inhibiting SDF-1? activity attenuated the cardioprotective effect of primary unloading. Twenty-eight days after AMI, primary unloading reduced LV scar size, improved cardiac function, and limited expression of biomarkers associated with heart failure and maladaptive remodeling. CONCLUSIONS:The authors report for the first time that first mechanically reducing LV work before coronary reperfusion with a transvalvular pump is necessary and sufficient to reduce infarct size and to activate a cardioprotective program that includes enhanced SDF-1? activity. Primary unloading further improved LV scar size and cardiac function 28 days after AMI.

Dataset Information

Acute Left Ventricular Unloading Reduces Atrial Stretch and Inhibits Atrial Arrhythmias.

Publications

Acute Left Ventricular Unloading Reduces Atrial Stretch and Inhibits Atrial Arrhythmias.

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