Cardiovascular magnetic resonance-derived left ventricular mechanics-strain, cardiac power and end-systolic elastance under various inotropic states in swine.
BACKGROUND
Cardiovascular magnetic resonance (CMR) strain imaging is an established technique to quantify myocardial deformation. However, to what extent left ventricular (LV) systolic strain, and therefore LV mechanics, reflects classical hemodynamic parameters under various inotropic states is still not completely clear. Therefore, the aim of this study was to investigate the correlation of LV global strain parameters measured via CMR feature tracking (CMR-FT, based on conventional cine balanced steady state free precession (bSSFP) images) with hemodynamic parameters such as cardiac index (CI), cardiac power output (CPO) and end-systolic elastance (Ees) under various inotropic states.


METHODS
Ten anaesthetized, healthy Landrace swine were acutely instrumented closed-chest and transported to the CMR facility for measurements. After baseline measurements, two steps were performed: (1) dobutamine-stress (Dobutamine) and (2) verapamil-induced cardiovascular depression (Verapamil). During each protocol, CMR images were acquired in the short axisand apical 2Ch, 3Ch and 4Ch views. MEDIS software was utilized to analyze global longitudinal (GLS), global circumferential (GCS), and global radial strain (GRS).


RESULTS
Dobutamine significantly increased heart rate, CI, CPO and Ees, while Verapamil decreased them. Absolute values of GLS, GCS and GRS accordingly increased during Dobutamine infusion, while GLS and GCS decreased during Verapamil. Linear regression analysis showed a moderate correlation between GLS, GCS and LV hemodynamic parameters, while GRS correlated poorly. Indexing global strain parameters for indirect measures of afterload, such as mean aortic pressure or wall stress, significantly improved these correlations, with GLS indexed for wall stress reflecting LV contractility as the clinically widespread LV ejection fraction.


CONCLUSION
GLS and GCS correlate accordingly with LV hemodynamics under various inotropic states in swine. Indexing strain parameters for indirect measures of afterload substantially improves this correlation, with GLS being as good as LV ejection fraction in reflecting LV contractility. CMR-FT-strain imaging may be a quick and promising tool to characterize LV hemodynamics in patients with varying degrees of LV dysfunction.
['Faragli|A|A|', 'Tanacli|R|R|', 'Kolp|C|C|', 'Abawi|D|D|', 'Lapinskas|T|T|', 'Stehning|C|C|', 'Schnackenburg|B|B|', 'Lo Muzio|F P|FP|', 'Fassina|L|L|', 'Pieske|B|B|', 'Nagel|E|E|', 'Post|H|H|', 'Kelle|S|S|', 'Alogna|A|A|']
D000818:Animals D001696:Biomechanical Phenomena D002121:Calcium Channel Blockers D002316:Cardiotonic Agents D005260:Female D006352:Heart Ventricles D006439:Hemodynamics D019028:Magnetic Resonance Imaging, Cine D011237:Predictive Value of Tests D034421:Sus scrofa D013599:Systole D013997:Time Factors D016277:Ventricular Function, Left
Cardiovascular magnetic resonance Hemodynamics Feature tracking Contractile function Left ventricular strain Porcine model Translational studies