June Yamrozik

Physiologic compensation is supranormal in compensated aortic stenosis: does it return to normal after aortic valve replacement or is it blunted by coexistent coronary artery disease? An intramyocardial magnetic resonance imaging study.

BACKGROUND In compensated aortic stenosis (AS), cardiac performance measured at the ventricular chamber is typically supranormal, whereas measurements at the myocardium are often impaired. We investigated intramyocardial mechanics after aortic valve replacement (AVR) and the effects relative to the presence or absence of coronary artery disease (CAD+ or CAD-), respectively. METHODS AND RESULTS Twenty-nine patients (46 to 91 years, 10 female) with late but not decompensated AS underwent cardiovascular MRI before AVR (PRE), with follow-up at 6+/-1 (EARLY) and 13+/-2 months (LATE) to determine radiofrequency tissue-tagged left ventricle (LV) transmural circumferential strain, torsion, structure, and function. At the myocardial level, concentric LV hypertrophy regressed 18% LATE (93+/-22 versus 77+/-17 g/m2; P<0.0001), whereas at the LV chamber level, ejection fraction was supranormal PRE, 67+/-6% (ranging as high as 83%) decreasing to 59+/-6% LATE (P<0.05), representing not dysfunction but a return to more normal LV physiology. Between the CAD+ and CAD- groups, intramyocardial strain was similar PRE (19+/-10 versus 20+/-10) but different LATE, with dichotomization specifically related to the CAD state. In the CAD- patients, strain increased to 23+/-10% (+20%), whereas in CAD+ patients it fell to 16+/-11% (-26%), representing a nearly 50% decline after AVR (P<0.05). This was particularly evident at the apex, where CAD- strain LATE improved 17%, whereas for CAD+ it decreased 2.5-fold. Transmural strain and myocardial torsion followed a similar pattern, critically dependent on CAD. AVR impacted LV geometry and mitral apparatus, resulting in decreased mitral regurgitation, negating the double valve consideration. CONCLUSIONS In AS patients after AVR, reverse remodeling of the supranormal systolic function parallels improvement in cardiovascular MRI-derived regression of LV hypertrophy and LV intramyocardial strain. However, discordant effects are evident after AVR, driven by CAD status, suggesting that the typical AVR benefits are experienced disproportionately by those without CAD and not by those obliged to undergo concomitant coronary artery bypass grafting/AVR.

Contrast-enhanced CMR is equally effective as TEE in the evaluation of left atrial appendage thrombus in patients with atrial fibrillation undergoing pulmonary vein isolation procedure

BACKGROUND Patients with atrial fibrillation (AF) routinely undergo transesophageal echocardiography (TEE) for the evaluation of the left atrial appendage (LAA) to rule out thrombus prior to undergoing pulmonary vein isolation (PVI). Cardiac magnetic resonance (CMR) is now increasingly used for the evaluation of patients with AF to define pulmonary vein (PV) anatomy prior to PVI. OBJECTIVE To hypothesize that a retrospective comparison of 2-dimensional/3-dimensional (2D/3D) contrast-enhanced CMR sequences with TEE for the evaluation of LAA thrombus in patients with AF selected for PVI will demonstrate equivalence. METHODS Ninety-seven (N = 97) consecutive patients with AF underwent near-simultaneous TEE and noncontrast and contrast CMR prior to undergoing an initial PVI procedure. The CMR images were analyzed in 2 categories: (1) the 2D noncontrast cine images and early gadolinium enhancement images showing LAA and (2) 3D contrast source images acquired during PV magnetic resonance angiography. CMR variables evaluated were the presence or absence of LAA thrombus and the quality of images, and they were compared with the results of TEE in a blinded fashion. RESULTS All subjects were analyzed for the presence or absence of LAA thrombus. Thrombus was absent in 98% of the patients on both TEE and CMR and present in 2% on both studies (100% correlation). In 6 subjects, 2D cine CMR images were indeterminate whereas all 2D early gadolinium enhancement images and 3D contrast images were successful in excluding LAA thrombus. There was 100% concordance between CMR and TEE for the final diagnosis of LAA thrombus. CONCLUSIONS In one single examination, CMR offers a comparable alternative to TEE for the complete noninvasive evaluation of LAA thrombus and PV anatomy in patients with AF referred for PVI without obligate need for TEE.

Effect of a Flexible Ventricular Restraint Device on Cardiac Remodeling after Acute Myocardial Infarction

The effects of a flexible ventricular restraint device on left ventricular (LV) dilatation and hypertrophy after transmural infarction are examined in an ovine model. Left ventricular remodeling and dilatation occurs after extensive myocardial infarction. A flexible ventricular restraint made from a nitinol mesh was evaluated in adult female sheep (n = 14). Cardiac magnetic resonance imaging scans and hemodynamic measurements were completed before and 6 weeks after anterior myocardial infarction. Treatment animals (n = 7) received passive ventricular restraint concurrently with LV infarction; the others (n = 7) served as controls. Increases in LV end-diastolic volume index were significantly less in the restraint group than in controls (0.20 ± 0.41 vs 0.83 ± 0.50 ml/kg, p < 0.03). End-systolic volumes increased less in treatment animals (0.43 ± 0.28 vs 0.90 ± 0.38 ml/kg, p < 0.03). Control hearts showed an increase in LV mass after infraction, whereas LV mass decreased in restrained hearts (0.14 ± 0.19 vs −0.25 ± 0.36 g/kg, p < 0.03). Hemodynamic studies showed similar changes after infarction for the control and the device group. Gross and microscopic examination showed no device-induced epicardial injury. A flexible ventricular restraint device attenuated remodeling after acute myocardial infarction in sheep.

Ex vivo cardiovascular magnetic resonance measurements of right and left ventricular mass compared with direct mass measurement in excised hearts after transplantation: a first human SSFP comparison

BackgroundCMR is considered the `gold standard’ for non-invasive LV and RV mass quantitation. This information is solely based on gradient-recalled echo (GRE) sequences while contrast dependent on intrinsic T1/T2 characteristics potentially offers superior image contrast between blood and myocardium. This study aims, for the first time in humans, to validate the SSFP approach using explanted hearts obtained from heart transplant recipients. Our objective is establish the correlation between and to validate steady-state free precession (SSFP) derived LV and RV mass vs. autopsy mass of hearts from cardiac transplants patients.MethodsOver three-years, 58 explanted cardiomyopathy hearts were obtained immediately upon orthotopic heart transplantation from the OR. They were quickly cleaned, prepared and suspended in a saline-filled container and scanned ex vivo via SSFP-SA slices to define LV/RV mass. Using an automatic thresholding program, segmentation was achieved in combination with manual trimming (ATMT) of extraneous tissue incorporating 3D cardiac modeling performed by independent and blinded readers. The explanted hearts were then dissected with the ventricles surgically separated at the interventricular septum. Weights of the total heart not excluding papillary and trabecular myocardium, LV and RV were measured via high-fidelity scale. Linear regression and Bland-Altman plots were used to analyze the data. The intra-class correlation coefficient was used to assess intra-observer reliability.ResultsOf the total of 58 explanted hearts, 3 (6%) were excluded due to poor image quality leaving 55 patients (94%) for the final analysis. Significant positive correlations were found between total 3D CMR mass (450 ± 111 g) and total pathology mass (445 ± 116 g; r = 0.99, p < 0.001) as well as 3D CMR measured LV mass (301 ± 93 g) and the pathology measured LV mass (313 ± 96 g; r = 0.95, p < 0.001). Strong positive correlations were demonstrated between the 3D CMR measured RV mass (149 ± 46 g) and the pathology measured RV mass (128 ± 40 g; r = 0.76, p < 0.001). The mean bias between 3D-CMR and pathology measures for total mass, LV mass and RV mass were: 3.0 g, -16 g and 19 g, respectively.ConclusionsSSFP-CMR accurately determines total myocardial, LV and RV mass as compared to pathology weighed explanted hearts despite variable surgical removal of instrumentation (left and right ventricular assist devices, AICD and often apical core removals). Thus, this becomes the first-ever human CMR confirmation for SSFP now validating the distinction of `gold standard’.

Exploratory use of cardiovascular magnetic resonance imaging in liver transplantation: a one-stop shop for preoperative cardiohepatic evaluation.

Background Preoperative cardiovascular risk stratification in orthotopic liver transplantation candidates has proven challenging due to limitations of current noninvasive modalities. Additionally, the preoperative workup is logistically cumbersome and expensive given the need for separate cardiac, vascular, and abdominal imaging. We evaluated the feasibility of a “one-stop shop” in a magnetic resonance suite, performing assessment of cardiac structure, function, and viability, along with simultaneous evaluation of thoracoabdominal vasculature and liver anatomy. Methods In this pilot study, patients underwent steady-state free precession sequences and stress cardiac magnetic resonance (CMR), thoracoabdominal magnetic resonance angiography, and abdominal magnetic resonance imaging (MRI) on a standard MRI scanner. Pharmacologic stress was performed using regadenoson, adenosine, or dobutamine. Viability was assessed using late gadolinium enhancement. Results Over 2 years, 51 of 77 liver transplant candidates (mean age, 56 years; 35% female; mean Model for End-stage Liver Disease score, 10.8; range, 6–40) underwent MRI. All referred patients completed standard dynamic CMR, 98% completed stress CMR, 82% completed late gadolinium enhancement for viability, 94% completed liver MRI, and 88% completed magnetic resonance angiography. The mean duration of the entire study was 72 min, and 45 patients were able to complete the entire examination. Among all 51 patients, 4 required follow-up coronary angiography (3 for evidence of ischemia on perfusion CMR and 1 for postoperative ischemia), and none had flow-limiting coronary disease. Nine proceeded to orthotopic liver transplantation (mean 74 days to transplantation after MRI). There were six ascertained mortalities in the nontransplant group and one death in the transplanted group. Explant pathology confirmed 100% detection/exclusion of hepatocellular carcinoma. No complications during CMR examination were encountered. Conclusions In this proof-of-concept study, it appears feasible to perform a comprehensive, efficient, and safe preoperative liver transplant imaging in a CMR suite—a one-stop shop, even in seriously ill patients.

Ventricular Tachycardia and Right Ventricular Fibrosis After Tetralogy of Fallot Surgical Repair

Ventricular tachyarrhythmias are known sequelae among adults with repaired tetralogy of Fallot. The incidence of sustained ventricular tachycardia and sudden cardiac death in patients 35 years after corrective surgery is estimated at 11.9% and 8.3%, respectively.1 Studies have shown that right ventricular enlargement resulting from chronic pulmonic regurgitation is the most common hemodynamic substrate.2 QRS prolongation (>180 milliseconds) is one of the most sensitive ECG predictors and in turn correlates with right ventricular (RV) dilation.3 The exact mechanism is not as well studied as that of left ventricular arrhythmias, but it is purported that volume overload leads to RV myocardial stretching and RV fibrosis and hence serves as an arrhythmogenic focus. The anatomic location of the RV pathology leading to ventricular tachyarrhythmias after tetralogy of Fallot surgical repair is not well defined. The basal portions of the RV …

Evaluation of cardiac valvular regurgitant lesions by cardiac MRI sequences: comparison of a four valve semi-quantitative vs. quantitative approach.

BACKGROUND AND AIM OF THE STUDY Cardiac magnetic resonance (CMR) imaging generally allows a more accurate and valid quantification of cardiac function, mass and regurgitant volumes than echocardiography. Although recent technological advancements in CMR have made the evaluation of cardiac valves more reliable, no studies have yet been conducted to compare semi-quantitative grading (SQG) using CMR steady-state free precession (SSFP) sequences with quantitative grading (QG) based on stroke volumes and phase-velocity mapping (PVM). It is proposed that the SQG of cardiac valvular regurgitations based on CMR SSFP sequences is feasible, and highly correlative with standard CMR QG methods. METHODS CMR data obtained between January 2007 and December 2011 was evaluated prospectively for valvular regurgitant lesions. Patients were included if they had right and left ventricular volumetrics based on CMR SSFP sequences and PVM across the aortic and pulmonic valves with reported regurgitant volumes and fractions. Patients were excluded if they had prosthetic valves, cardiac arrhythmias and intra-cardiac shunts. Regurgitant lesions were semi-quantitatively (visually) graded on a standard scale of 0 to 4 (trace, mild, moderate, moderate to severe, and severe) and compared with quantitative regurgitant fractions. Correlations were evaluated by Spearmans rho formula, and kappa for intra- and inter-observer variabilities were obtained on 30% of the study sample. RESULTS A total of 97 patients (58 males, 39 females; average age 55 +/- 18 years) representing 134 valvular regurgitations [mitral (MR), aortic (AR), tricuspid (TR), and pulmonary (PR)] were analyzed by semiquantitative and quantitative methods. The regurgitant lesions included 44 mitral, 50 aortic, 29 tricuspid, and 11 pulmonary. The correlation between SQR versus QG yielded the following results: 0.67, p < 0.001 (MR, r = 0.66, p < 0.001; AR, r = 0.68, p < 0.002; TR, r = 0.68, p = 0.001; PR, r = 0.70, p = 0.017). The results for QG versus SQG accounting for clinically significant differences of +/- 1 grade for the group were as follows: 0.95, p < 0.001 (MR, r = 0.91, p < 0.001; AR, r = 0.96, p < 0.001; TR, r = 0.99, p < 0.001; PR, r = 0.93, p < 0.001). No discrepancy between surgical regurgitation was present (3+ versus 4+). Weighted kappa results were 0.67 and 0.61 for intra- and inter-observer variabilities. CONCLUSION The visual assessment of cardiac regurgitant lesions is reliable, accurate and reproducible when compared to formal quantitative analysis via CMR. This confirms a robust role for CMR in assessing regurgitant lesions, particularly for surgical decision-making. These results were applicable to patients in sinus rhythm at the time of scanning.

Geometria da valva mitral derivada da ressonância magnética cardiovascular na avaliação da gravidade da regurgitação mitral

BACKGROUND Mitral regurgitation is the most common valvular heart disease worldwide. Magnetic resonance may be a useful tool to analyze mitral valve parameters. OBJECTIVE To distinguish mitral valve geometric patterns in patients with different severities of mitral regurgitation (MR) based on cardiovascular magnetic resonance imaging. METHODS Sixty-three patients underwent cardiovascular magnetic resonance imaging. Mitral valve parameters analyzed were: tenting area (mm2) and angle (degrees), ventricle height (mm), tenting height (mm), anterior leaflet, posterior leaflet length and annulus diameter (mm). Patients were divided into two groups, one including patients who required mitral valve surgery and another which did not. RESULTS Thirty-six patients had trace to mild (1-2+) MR and 27 had moderate to severe MR (3-4+). Ten (15.9%) out of 63 patients underwent surgery. Patients with more severe MR had a larger left ventricle end systolic diameter (38.6 ± 10.2 vs 45.4 ± 16.8, p<0.05) and left end diastolic diameter (52.9 ± 6.8 vs 60.1 ± 12.3, p= 0.005). On multivariate analysis, the tenting area was the strongest determinant of MR severity (r= 0.62, p=0.035). Annulus length (36.1 ± 4.7 vs 41 ± 6.7, p< 0.001), tenting area (190.7 ± 149.7 vs 130 ± 71.3, p= 0.048) and posterior leaflet length (15.1 ± 4.1 vs 12.2 ± 3.5, p= 0.023) were larger on patients requiring mitral valve surgery. CONCLUSIONS Tenting area, annulus and posterior leaflet length are possible determinants of MR severity. These geometric parameters could be used to determine severity and could, in the future, direct specific patient care based on individual mitral apparatus anatomy.

Does the presence of Q waves on the EKG accurately predict prior myocardial infarction when compared to cardiac magnetic resonance using late gadolinium enhancement? A cross-population study of noninfarct vs infarct patients

BACKGROUND We hypothesize that infarct detection by electrocardiogram (EKG) is inaccurate as compared with detection by magnetic resonance imaging and is potentially independent of infarct vs noninfarct status. This might have implications for societies in which initial cardiovascular testing is uniformly EKG. OBJECTIVE This study aimed to relate EKG-defined scar to cardiovascular magnetic resonance imaging (CMR)-defined scar independent of the underlying myocardial pathology. METHODS A total of 235 consecutive patients who underwent CMR-late gadolinium enhancement (LGE) with simultaneous EKG were screened for Q waves and compared with patients with a positive LGE pattern. The patients were divided into 3 groups: (1) patients with a positive infarct LGE pattern (LGE+/+; herein defined as LGE+), (2) patients with a noninfarct LGE pattern (LGE+/-), and (3) patients with a negative LGE pattern (LGE-). RESULTS While 139 of 235 patients (59%) were either LGE+ or LGE+/-, pathological Q waves were present in only 74 of 235 patients (31%). However, of these LGE+ or LGE+/- patients, only 76 (32%) had an infarct LGE pattern representing little overlap between the presence of LGE+ and Q waves. EKG sensitivity and specificity to detect infarct: 66% and 85%, respectively. However, of 24 of 74 patients (32%) with Q waves on the EKG, 66% were LGE+/- and 34% were LGE-. Importantly, 3-dimensional volume of myocardial scar was far more predictive of a Q wave than of scar transmurality. CONCLUSION EKG-defined scar, while ubiquitous for an infarct, has low sensitivity than CMR-LGE-defined scar. Unexpectedly, a significant number of pathological Q waves had absent infarct etiology, indicating high false positivity. Similarly, underrecognition of bona fide myocardial infarction frequently occurs, while 3-dimensional CMR volume of myocardial scar is far more predictive of a Q wave than of scar transmurality. This suggests that the well-regarded EKG may be a disservice when applied on a population basis, leading to inappropriate over or under downstream testing with wide socioeconomic implications.

Is cardiovascular MRI equally effective as TEE in evaluation of left atrial appendage thrombus in patients with atrial fibrillation undergoing pulmonary vein isolation

Patients with atrial fibrillation (Afib) routinely undergo a transesophageal echocardiogram (TEE) for evaluation of the left atrial appendage (LAA) to rule out thrombus prior to undergoing cardioversion or pulmonary vein isolation (PVI). Cardiac MRI (CMR) is now increasingly used for evaluation of these patients for defining pulmonary vein anatomy prior to PVI. We hypothesized that 2D and 3D non-contrast and contrast CMR is as effective as TEE in evaluating for LAA thrombus while providing simultaneous comprehensive non-invasive evaluation of the pulmonary vein anatomy within a single exam.