Abstract:Cardiovascular magnetic resonance feature tracking (CMR-FT) is a novel technique for non-invasive assessment of myocardial motion and deformation. Although CMR-FT is standardized in humans, literature on comparative analysis from animal models is scarce. In this study, we measured the reproducibility of global strain under various inotropic states and the sample size needed to test its relative changes in pigs. Ten anesthetized healthy Landrace pigs were investigated. After baseline (BL), two further steps wer… Show more
“…In line with previous reproducibility studies [ 39 – 42 ], we showed that radial strain is a poorly reproducible and inaccurate measurement. In this study we did not show the inter- and intra-observer reproducibility because it was already assessed in a previous work from our group based on the same cohort [ 43 ]. Our analysis showed that measurements at baseline were good to excellent (good ICC 0.60–0.74; excellent ICC > 0.74) for GLS, GCS and GRS, but that only GLS and GCS displayed good reproducibility during both dobutamine and verapamil steps, whereas radial strain was highly variable [ 43 ].…”
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.
“…In line with previous reproducibility studies [ 39 – 42 ], we showed that radial strain is a poorly reproducible and inaccurate measurement. In this study we did not show the inter- and intra-observer reproducibility because it was already assessed in a previous work from our group based on the same cohort [ 43 ]. Our analysis showed that measurements at baseline were good to excellent (good ICC 0.60–0.74; excellent ICC > 0.74) for GLS, GCS and GRS, but that only GLS and GCS displayed good reproducibility during both dobutamine and verapamil steps, whereas radial strain was highly variable [ 43 ].…”
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.
“…Data from n = 10 (51 ± 10 kg) Landrace pigs were selected from an already published study cohort from our group (16,17), where dobutamine stress testing and verapamil ischemia induction were performed. Female Landrace swine were fasted overnight with free access to water and then sedated and intubated on the day of the experiment.…”
Section: Methodsmentioning
confidence: 99%
“…The experimental protocol has been already described in two published papers from our group (16,17). Briefly, female Landrace pigs (n = 10, weight = 51 ± 10 kg) were acutely instrumented, and the animals were transported to the MRI facility for measurements.…”
Section: Experimental Protocolmentioning
confidence: 99%
“…Internal myocardial power [baseline: 5.9 (4.6-8.5) W/m 2 ] was not affected by dobutamine [7.5 (6.9-9.0) W/m 2 , p = 0.241] nor verapamil [5.8 (4.7-8.8) W/m 2 , p = 0.878]. Myocardial efficiency did not change from baseline to dobutamine [21% (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) vs. 31% , p = 0.059] but decreased significantly during verapamil-induced ischemia [10% (8)(9)(10)(11)(12)(13), p = 0.005].…”
Background: Myocardial efficiency should be maintained stable under light-to-moderate stress conditions, but ischemia puts the myocardium at risk for impaired functionality. Additionally, the measurement of such efficiency typically requires invasive heart catheterization and exposure to ionizing radiation. In this work, we aimed to non-invasively assess myocardial power and the resulting efficiency during pharmacological stress testing and ischemia induction.Methods: In a cohort of n = 10 healthy Landrace pigs, dobutamine stress testing was performed, followed by verapamil-induced ischemia alongside cardiac magnetic resonance (CMR) imaging. External myocardial power, internal myocardial power, and myocardial efficiency were assessed non-invasively using geometrical and functional parameters from CMR volumetric as well as blood flow and pressure measurements.Results: External myocardial power significantly increased under dobutamine stress [2.3 (1.6–3.1) W/m2 vs. 1.3 (1.1–1.6) W/m2, p = 0.005] and significantly decreased under verapamil-induced ischemia [0.8 (0.5–0.9) W/m2, p = 0.005]. Internal myocardial power [baseline: 5.9 (4.6–8.5) W/m2] was not affected by dobutamine [7.5 (6.9–9.0) W/m2, p = 0.241] nor verapamil [5.8 (4.7–8.8) W/m2, p = 0.878]. Myocardial efficiency did not change from baseline to dobutamine [21% (15–27) vs. 31% (20–44), p = 0.059] but decreased significantly during verapamil-induced ischemia [10% (8–13), p = 0.005].Conclusion: In healthy Landrace pigs, dobutamine stress increased external myocardial power, whereas myocardial efficiency was maintained stable. On the contrary, verapamil-induced ischemia substantially decreased external myocardial power and myocardial efficiency. Non-invasive CMR was able to quantify these efficiency losses and might be useful for future clinical studies evaluating the effects of therapeutic interventions on myocardial energetics.
“…This multiparametric approach of strain measurements is beneficial as it provides a comprehensive assessment of various components of myocardial function over the cardiac cycle 16 , 17 . CMR-FT has also been translated to experimental animal models 15 , 18 , and has been reported to be reproducible in swine hearts 19 , and related to myocardial injury 20 , 21 . Figure 1 CMR as a non-invasive tool for assessing regional tissue, systolic and diastolic abnormalities.…”
Electric interventions are used to terminate arrhythmia. However, myocardial injury from the electrical intervention can follow unique pathways and it is unknown how this affects regional ventricular function. This study investigated the impact of transthoracic electrical shocks on systolic and diastolic myocardial deformation. Ten healthy anaesthetized female swine received five transthoracic shocks (5 × 200 J) and six controls underwent a cardiovascular magnetic resonance exam prior to and 5 h after the intervention. Serial transthoracic shocks led to a global reduction in both left (LV, − 15.6 ± 3.3% to − 13.0 ± 3.6%, p < 0.01) and right ventricular (RV, − 16.1 ± 2.3% to − 12.8 ± 4.2%, p = 0.03) peak circumferential strain as a marker of systolic function and to a decrease in LV early diastolic strain rate (1.19 ± 0.35/s to 0.95 ± 0.37/s, p = 0.02), assessed by feature tracking analysis. The extent of myocardial edema (ΔT1) was related to an aggravation of regional LV and RV diastolic dysfunction, whereas only RV systolic function was regionally associated with an increase in T1. In conclusion, serial transthoracic shocks in a healthy swine model attenuate biventricular systolic function, but it is the acute development of regional diastolic dysfunction that is associated with the onset of colocalized myocardial edema.
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