Three-dimensional echocardiographic assessment of left ventricular geometric changes following acute myocardial infarction.

Acute ST-segment elevation myocardial infarction (STEMI) is associated with left ventricular (LV) structural and functional consequences. We aimed to elucidate LV geometric changes following STEMI using three-dimensional (3D) echocardiography (3DE) and to assess their functional implications using two-dimensional (2D) speckle tracking echocardiography (STE). The study included 71 patients with STEMI who underwent baseline and 6-month follow-up 2D- and 3DE. Measured parameters included LV dimensions, biplane volumes, wall motion assessment, 2D LV global longitudinal strain (GLS), and 3D LV volumes, sphericity index and systolic dyssynchrony index. According to 3DE, LV geometric changes were classified as, adverse remodeling, reverse remodeling, and minimal LV volumetric changes. The occurrence of in-hospital and follow-up major adverse cardiovascular events (MACE) was assessed among the study population. The incidence of developing adverse remodeling was 25.4% while that of reverse remodeling was 36.6%. Adverse remodeling patients had significantly higher in-hospital MACE. Reverse remodeling was associated with significantly improved GLS, that was less evident in those with minimal LV geometric changes, and non-significant improvement for adverse remodeling group. LV baseline 2D GLS significantly correlated with follow-up 3D volumes among both reverse and adverse remodeling groups. Female gender and higher absolute GLS change upon follow-up were significantly associated with reverse remodeling. ROC-derived cutoff for adverse remodeling reallocated a substantial number of patients from the minimal change group to the adverse remodeling. Following acute STEMI, two-dimensional GLS was associated with and potentially predictive of changes in LV volumes as detected by three-dimensional echocardiography.

Cardiac magnetic resonance assessment of mitral regurgitation severity appears better than echocardiographic imaging.

The mitral valve surgery decision is made mainly according to echocardiographic (ECHO) criteria. As the asymptomatic patients are still candidates for surgery in some situations, this makes the accurate assessment of mitral regurgitation (MR) severity and cardiac dimensions even more important. We aimed to compare ECHO and cardiac magnetic resonance imaging (CMR) in the assessment of MR severity and cardiac dimensions. In this prospective study, we included all patients with more than mild MR by ECHO and referred to our university hospital from 1st of April 2017 and 1st of April 2019. Exclusion criteria were critically ill patients, presence of other valve lesions, planned revascularization, pregnancy and contraindication for CMR. All patients had full history taking, examination, body surface area, and ECG. MR severity and left atrial and left ventricular dimensions were assessed in 50 patients with both 2D-ECHO and CMR in the same day. There were no significant differences in baseline clinical characteristics between moderate (24 patients) and severe MR (26 patients) groups. Poor degree of agreement was present between CMR and ECHO assessment for MR severity (same degree of MR only in 36% (18/50 patients) with kappa grade = 0.19). Furthermore, ECHO overestimated grades of MR compared to CMR (severe MR in 52% vs. 38.4%, p = 0.01 respectively). Based on the etiology of MR, primary (30 patients) vs. secondary MR (20 patients) showed the same dis-agreement between CMR and ECHO assessment of MR severity. Left atrial and ventricular dimensions showed good agreement between CMR and ECHO. Our results suggest that CMR could be more accurate than ECHO in assessing the severity of MR especially in severe cases that need surgery.

Assessment of distribution and evolution of mechanical dyssynchrony in a porcine model of myocardial infarction by cardiovascular magnetic resonance.

BACKGROUND: We sought to investigate the relationship between infarct and dyssynchrony post- myocardial infarct (MI), in a porcine model. Mechanical dyssynchrony post-MI is associated with left ventricular (LV) remodeling and increased mortality. METHODS: Cine, gadolinium-contrast, and tagged cardiovascular magnetic resonance (CMR) were performed pre-MI, 9 ± 2 days (early post-MI), and 33 ± 10 days (late post-MI) post-MI in 6 pigs to characterize cardiac morphology, location and extent of MI, and regional mechanics. LV mechanics were assessed by circumferential strain (eC). Electro-anatomic mapping (EAM) was performed within 24 hrs of CMR and prior to sacrifice. RESULTS: Mean infarct size was 21 ± 4% of LV volume with evidence of post-MI remodeling. Global eC significantly decreased post MI (-27 ± 1.6% vs. -18 ± 2.5% (early) and -17 ± 2.7% (late), p < 0.0001) with no significant change in peri-MI and MI segments between early and late time-points. Time to peak strain (TTP) was significantly longer in MI, compared to normal and peri-MI segments, both early (440 ± 40 ms vs. 329 ± 40 ms and 332 ± 36 ms, respectively; p = 0.0002) and late post-MI (442 ± 63 ms vs. 321 ± 40 ms and 355 ± 61 ms, respectively; p = 0.012). The standard deviation of TTP in 16 segments (SD16) significantly increased post-MI: 28 ± 7 ms to 50 ± 10 ms (early, p = 0.012) to 54 ± 19 ms (late, p = 0.004), with no change between early and late post-MI time-points (p = 0.56). TTP was not related to reduction of segmental contractility. EAM revealed late electrical activation and greatly diminished conduction velocity in the infarct (5.7 ± 2.4 cm/s), when compared to peri-infarct (18.7 ± 10.3 cm/s) and remote myocardium (39 ± 20.5 cm/s). CONCLUSIONS: Mechanical dyssynchrony occurs early after MI and is the result of delayed electrical and mechanical activation in the infarct.

Strain-encoding cardiovascular magnetic resonance for assessment of right-ventricular regional function.

BACKGROUND: Tissue tagging by cardiovascular magnetic resonance (CMR) is a comprehensive method for the assessment of cardiac regional function. However, imaging the right ventricle (RV) using this technique is problematic due to the thin wall of the RV relative to tag spacing which limits assessment of regional function using conventional in-plane tagging. HYPOTHESIS: We hypothesize that the use of through-plane tags in the strain-encoding (SENC) CMR technique would result in reproducible measurements of the RV regional function due to the high image quality and spatial resolution possible with SENC. AIM: To test the intra- and inter-observer variabilities of RV peak systolic strain measurements with SENC CMR for assessment of RV regional function (systolic strain) in healthy volunteers. METHODS: Healthy volunteers (n = 21) were imaged using SENC. A four-chamber view was acquired in a single breath-hold. Circumferential strain was measured during systole at six equidistant points along the RV free wall. Peak contraction is defined as the maximum value of circumferential strain averaged from the six points, and regional function is defined as the strain value at each point at the time of peak contraction. RESULTS: Mean values for peak circumferential strain (+/- standard deviation) of the basal, mid, and apical regions of the RV free wall were -20.4 +/- 2.9%, -18.8 +/- 3.9%, and -16.5 +/- 5.7%, Altman plots showed good intra- and inter-observer agreements with mean difference of 0.11% and 0.32% and limits of agreement of -4.038 to 4.174 and -4.903 to 5.836, respectively. CONCLUSION: SENC CMR allows for rapid quantification of RV regional function with low intra- and inter-observer variabilities, which could permit accurate quantification of regional strain in patients with RV dysfunction.