The effect of obesity on regadenoson-induced myocardial hyperemia: a quantitative magnetic resonance imaging study.

The A2(A) receptor agonist, regadenoson, is increasingly used as a vasodilator during nuclear myocardial perfusion imaging. Regadenoson is administered as a single, fixed dose. Given the frequency of obesity in patients with symptoms of heart disease, it is important to know whether the fixed dose of regadenoson produces maximal coronary hyperemia in subjects of widely varying body size. Thirty subjects (12 female, 18 male, mean BMI 30.3 ± 6.5, range 19.6-46.6) were imaged on a 3T magnetic resonance scanner. Imaging with a saturation recovery radial turboFLASH sequence was done first at rest, then during adenosine infusion (140 µg/kg/min) and 30 min later with regadenoson (0.4 mg/5 ml bolus). A 5 cc/s injection of Gd-BOPTA was used for each perfusion sequence, with doses of 0.02, 0.03 and 0.03 mmol/kg, respectively. Analysis of the upslope of myocardial time-intensity curves and quantitative processing to obtain myocardial perfusion reserve (MPR) values were performed for each vasodilator. The tissue upslopes for adenosine and regadenoson matched closely (y = 1.1x + 0.03, r = 0.9). Mean MPR was 2.3 ± 0.6 for adenosine and 2.4 ± 0.9 for regadenoson (p = 0.14). There was good agreement between MPR measured with adenosine and regadenoson (y = 1.1x - 0.06, r = 0.7). The MPR values measured with both agents tended to be lower as BMI increased. There were no complications during administration of either agent. Regadenoson produced fewer side effects. Fixed dose regadenoson and weight adjusted adenosine produce similar measures of MPR in patients with a wide range of body sizes. Regadenoson is a potentially useful vasodilator for stress MRI studies.

High prevalence of right ventricular dysfunction in ICD patients with shocks: a potential new predictor in risk stratification.

BACKGROUND: Despite identifying several risk factors for sudden cardiac death, our ability to predict arrhythmic events in patients with an implantable cardioverter defibrillator (ICD) remains poor. The purpose of this study was to determine if patients who received appropriate ICD shocks had a higher degree of right ventricular (RV) dysfunction at baseline when compared to patients who did not receive ICD shocks. METHODS: We conducted a 1:2 case-control, retrospective study comparing RV end-diastolic and end-systolic areas (RV ED and RV ES areas, respectively), fractional RV area change, and RV wall thickness in 19 consecutive patients who received appropriate ICD shocks (shock group) with another group of 38 patients who did not receive ICD shocks (no-shock group). RESULTS: There was no significant difference in the RV end-diastolic areas between the groups. However, patients who experienced ICD shocks had a higher RV end-systolic area and a lower RV fractional area change when compared to patients without ICD shocks, 16.3 ± 4.9 cm(2) and 27.7 ± 9.0% in the shock group versus 14.2 ± 4.4 cm(2) and 35.8 ± 10.3% in the no-shock group; (p = 0.08 and 0.004, respectively). Furthermore, the RV wall thickness was greater in patients with ICD shocks when compared to patients without ICD shocks, 0.49 ± 0.05 cm and 0.44 ± 0.04 cm, respectively (p = 0.001). Utilizing a logistic regression analysis and after controlling for variables with univariate significance (p < 0.1), RV wall thickness independently predicted ICD shocks (OR 13.9 mm(-1) change of RV thickness, p = 0.004). CONCLUSION: Our findings suggest that some measurements of RV function might prove to be useful in predicting future arrhythmic events. Additional prospective studies are needed to test this hypothesis.

Atrial fibrosis helps select the appropriate patient and strategy in catheter ablation of atrial fibrillation: a DE-MRI guided approach.

UNLABELLED: MRI for AF Patient Selection and Ablation Approach. INTRODUCTION: Left atrial (LA) fibrosis and ablation related scarring are major predictors of success in rhythm control of atrial fibrillation (AF). We used delayed enhancement MRI (DE-MRI) to stratify AF patients based on pre-ablation fibrosis and also to evaluate ablation-induced scarring in order to identify predictors of a successful ablation. METHODS AND RESULTS: One hundred and forty-four patients were staged by percent of fibrosis quantified with DE-MRI, relative to the LA wall volume: minimal or Utah stage 1; <5%, mild or Utah stage 2; 5-20%, moderate or Utah stage 3; 20-35%, and extensive or Utah stage 4; >35%. All patients underwent pulmonary vein (PV) isolation and posterior wall and septal debulking. Overall, LA scarring was quantified and PV antra were evaluated for circumferential scarring 3 months post ablation. LA scarring post ablation was comparable across the 4 stages. Most patients had either no (36.8%) or 1 PV (32.6%) antrum circumferentially scarred. Forty-two patients (29%) had recurrent AF over 283 ± 167 days. No recurrences were noted in Utah stage 1. Recurrence was 28% in Utah stage 2, 35% in Utah stage 3, and 56% in Utah stage 4. Recurrence was predicted by circumferential PV scarring in Utah stage 2 and by overall LA wall scarring in Utah stage 3. No recurrence predictors were identified in Utah stage 4. CONCLUSIONS: Circumferential PV antral scarring predicts ablation success in mild LA fibrosis, while posterior wall and septal scarring is needed for moderate fibrosis. This may help select the proper candidate and strategy in catheter ablation of AF.

Echocardiographic left atrial reverse remodeling after catheter ablation of atrial fibrillation is predicted by preablation delayed enhancement of left atrium by magnetic resonance imaging.

BACKGROUND: Atrial fibrosis is a hallmark of atrial structural remodeling (SRM) and leads to structural and functional impairment of left atrial (LA) and persistence of atrial fibrillation (AF). This study was conducted to assess LA reverse remodeling after catheter ablation of AF in mild and moderate-severe LA SRM. METHODS: Catheter ablation was performed in 68 patients (age 62 ± 14 years, 68% males) with paroxysmal (n = 26) and persistent (n = 42) AF. The patients were divided into group 1 with mild LA SRM (<10%, n = 31) and group 2 with moderate-severe LA SRM (>10%, n = 37) by delayed enhancement magnetic resonance imaging (DEMRI). Two-dimensional echocardiography, LA strain, and strain rate during left ventricular systole by velocity vector imaging were performed pre and at 6 ± 3 months postablation. The long-term outcome was monitored for 12 months. RESULTS: Patients in group 1 were younger (57 ± 15 vs 66 ± 13 years, P = .009) with a male predominance (80% vs 57%, P < .05) as compared to group 2. Postablation, group 1 had significant increase in average LA strain (Δ↑: 14% vs 4%, P < .05) and strain rate (Δ↑: 0.5 vs 0.1 cm/s, P < .05) as compared to group 2. There was a trend toward more patients with persistent AF in group 2 (68% vs 55%, P = .2), but it was not statistically significant. Group 2 had more AF recurrences (41% vs 16%, P = .02) at 12 months after ablation. CONCLUSION: Mild preablation LA SRM by DEMRI predicts favorable LA structural and functional reverse remodeling and long-term success after catheter ablation of AF, irrespective of the paroxysmal or persistent nature of AF.

Can echocardiographic evaluation of cardiopulmonary hemodynamics decrease right heart catheterizations in end-stage heart failure patients awaiting transplantation?

Candidacy for heart transplantation is influenced by the severity of pulmonary hypertension. In this study, invasive hemodynamics from right-sided cardiac catheterization were compared with values obtained by validated equations from Doppler 2-dimensional transthoracic echocardiography. This prospective study was conducted in 40 patients with end-stage heart failure evaluated for heart transplantation or ventricular assist device implantation. Transthoracic echocardiography and right-sided cardiac catheterization were performed within 4 hours. From continuous-wave Doppler of the tricuspid regurgitation jet, pulmonary artery systolic pressure was calculated as the peak gradient across the tricuspid valve plus right atrial pressure estimated from inferior vena cava filling. Mean pulmonary artery pressure was calculated as (0.61 × pulmonary artery systolic pressure) + 2. Pulmonary vascular resistance (PVR) was calculated as (tricuspid regurgitation velocity/right ventricular outflow tract time-velocity integral × 10) + 0.16. Pulmonary capillary wedge pressure was calculated as 1.91 + (1.24 × E/E'). Pearson's correlation and Bland-Altman analysis of mean differences between echocardiographic and right-sided cardiac catheterization measurements were statistically significant for all hemodynamic parameters (pulmonary artery systolic pressure: r = 0.82, p < 0.05, mean difference 3.1 mm Hg, 95% confidence interval [CI] -0.2 to 6.3; mean pulmonary artery pressure: r = 0.80, p < 0.05, mean difference 2.5 mm Hg, 95% CI 0.3 to 4.6; PVR: r = 0.52, p < 0.05, mean difference 0.8 Wood units, 95% CI 0.3 to 1.4; pulmonary capillary wedge pressure: r = 0.65, p < 0.05, mean difference 2.2 mm Hg, 95% CI 0.1 to 4.3). Compared with right-sided cardiac catheterization, PVR by Doppler echocardiography identified all patients with PVR > 4 Wood units (n = 4), 73% of patients with PVR <2 Wood units (n = 8), and 52% of patients with PVR from 2 to 4 Wood units (n = 10). In conclusion, echocardiographic estimation of cardiopulmonary hemodynamics is reliable in patients with end-stage cardiomyopathy. The noninvasive assessment of hemodynamics by echocardiography may be able to decrease the number of serial right-sided cardiac catheterizations in selected patients awaiting heart transplantation. However, in patients with borderline PVR, right-sided cardiac catheterization is indicated to assess eligibility for transplantation.

Utility of intracardiac echocardiography for atrial baffle leak closure in repaired transposition of the great arteries.

A 27-year-old male with dextro-transposition of great arteries had Senning atrial switch repair in childhood and dual-chamber pacemaker placement for sinus node dysfunction in adulthood. Transthoracic echocardiography showed a lead in the systemic (anatomic right) ventricle. Multidetector computed tomography showed the lead perforating the baffle in the region of the body of the systemic venous atrium into the systemic ventricle. The lead was extracted, and a new lead was placed in the pulmonary (anatomic left) ventricle. A bidirectional baffle shunt persisted. The iatrogenic baffle leak was percutaneously closed with an Amplatzer septal occluder device using both intracardiac echocardiography (ICE) and three-dimensional transesophageal echocardiography (3D-TEE). We report the first use of ICE for baffle leak closure, which provided a good definition of the complex anatomy and guided the procedure.

Endomyocardial biopsy of right atrial angiosarcoma guided by intracardiac echocardiography.

We report a case of a 22-year-old female who presented with pericardial effusion and cardiac tamponade. She was diagnosed with a right atrial mass by computed tomography and was referred to our institution for biopsy of this mass. Transcatheter biopsy was performed with intracardiac echocardiography (ICE) guidance, avoiding the need for transesophageal echocardiography or surgery to obtain the biopsy. ICE for transcatheter biopsy of an intracardiac mass is an attractive modality which provides precise localization of the cardiac structures.

Evaluation of left atrial lesions after initial and repeat atrial fibrillation ablation: lessons learned from delayed-enhancement MRI in repeat ablation procedures.

BACKGROUND: We evaluated scar lesions after initial and repeat catheter ablation of atrial fibrillation (AF) and correlated these regions to low-voltage tissue on repeat electroanatomic mapping. We also identified gaps in lesion sets that could be targeted and closed during repeat procedures. METHODS AND RESULTS: One hundred forty-four patients underwent AF ablation and received a delayed-enhancement MRI at 3 months after ablation. The number of pulmonary veins (PV) with circumferential lesions were assessed and correlated with procedural outcome. Eighteen patients with AF recurrence underwent repeat ablation. MRI scar regions were compared with electroanatomic maps during the repeat procedure. Regions of incomplete scar around the PVs were then identified and targeted during repeat ablation to ensure complete circumferential lesions. After the initial procedure, complete circumferential scarring of all 4 PV antrum (PVA) was achieved in only 7% of patients, with the majority of patients (69%) having <2 completely scarred PVA. After the first procedure, the number of PVs with complete circumferential scarring and total left atrial wall (LA) scar burden was associated with better clinical outcome. Patients with successful AF termination had higher average total left atrial wall scar of 16.4%+/-9.8 (P=0.004) and percent PVA scar of 66.2+/-25.4 (P=0.01) compared with patients with AF recurrence who had an average total LA wall scar 11.3%+/-8.1 and PVA percent scar 50.0+/-24.7. In patients who underwent repeat ablation, the PVA scar percentage was 56.1%+/-21.4 after the first procedure compared with 77.2%+/-19.5 after the second procedure. The average total LA scar after the first ablation was 11.0%+/-4.1, whereas the average total LA scar after second ablation was 21.2%+/-7.4. All patients had an increased number of completely scarred pulmonary vein antra after the second procedure. MRI scar after the first procedure and low-voltage regions on electroanatomic mapping obtained during repeat ablation demonstrated a positive quantitative correlation of R(2)=0.57. CONCLUSIONS: Complete circumferential PV scarring difficult to achieve but is associated with better clinical outcome. Delayed-enhancement MRI can accurately define scar lesions after AF ablation and can be used to target breaks in lesion sets during repeat ablation.

Left atrial strain and strain rate in patients with paroxysmal and persistent atrial fibrillation: relationship to left atrial structural remodeling detected by delayed-enhancement MRI.

BACKGROUND: Atrial fibrillation (AF) is a progressive condition that begins with hemodynamic and/or structural changes in the left atrium (LA) and evolves through paroxysmal and persistent stages. Because of limitations with current noninvasive imaging techniques, the relationship between LA structure and function is not well understood. METHODS AND RESULTS: Sixty-five patients (age, 61.2+/-14.2 years; 67% men) with paroxysmal (44%) or persistent (56%) AF underwent 3D delayed-enhancement MRI. Segmentation of the LA wall was performed and degree of enhancement (fibrosis) was determined using a semiautomated quantification algorithm. Two-dimensional echocardiography and longitudinal LA strain and strain rate during ventricular systole with velocity vector imaging were obtained. Mean fibrosis was 17.8+/-14.5%. Log-transformed fibrosis values correlated inversely with LA midlateral strain (r=-0.5, P=0.003) and strain rate (r=-0.4, P<0.005). Patients with persistent AF as compared with paroxysmal AF had more fibrosis (22+/-17% versus 14+/-9%, P=0.04) and lower midseptal (27+/-14% versus 38+/-16%, P=0.01) and midlateral (35+/-16% versus 45+/-14% P=0.03) strains. Multivariable stepwise regression showed that midlateral strain (r=-0.5, P=0.006) and strain rate (r=-0.4, P=0.01) inversely predicted the extent of fibrosis independent of other echocardiographic parameters and the rhythm during imaging. CONCLUSIONS: LA wall fibrosis by delayed-enhancement MRI is inversely related to LA strain and strain rate, and these are related to the AF burden. Echocardiographic assessment of LA structural and functional remodeling is quick and feasible and may be helpful in predicting outcomes in AF.

Dyssynchrony Assessment with Tissue Doppler Imaging and Regional Volumetric Analysis by 3D Echocardiography Do Not Predict Long-Term Response to Cardiac Resynchronization Therapy.

Background. Currently there are no reliable predictors of response to cardiac resynchronization therapy (CRT) before implantation. We compared pre-CRT left ventricular (LV) dyssynchrony by tissue Doppler imaging (TDI) and regional volumetric analysis by 3-dimensional transthoracic echocardiography (3DTTE) in predicting response to CRT. Methods. Thirty-eight patients (79% nonischemic cardiomyopathy) with symptomatic heart failure who underwent CRT were enrolled. Clinical and echocardiographic responses were defined as improvement in one NYHA class and reduction in LV end-systolic volume by ≥15% respectively. Functional status was assessed by Minnesota Living with Heart Failure questionnaire and 6-minute walk distance. Results. In 33 patients, after CRT for 7.86 ± 2.27 months, there were 24 (73%) clinical and 19 (58%) echocardiographic responders. Functional parameters, LV dimensions, volumes and synchrony by TDI and 3DTTE improved significantly in responders. There was no difference in the number of responders and nonresponders when cut-off values for dyssynchrony by different measurements validated in other trials were applied. Area under receiver-operating-characteristic curve ranged from 0.4 to 0.6. Conclusion. CRT improves clinical and echocardiographic parameters in patients with systolic heart failure. The dyssynchrony measurements by TDI and 3DTTE are not comparable and are unable to predict response to CRT.

Short-term and long-term success of electrical cardioversion in atrial fibrillation in managed care system.

BACKGROUND: Initial success of electrical cardioversion (ECV) of atrial fibrillation (AF) has been reported in several studies as 50%-90%, of which only 50% patients remain in sinus rhythm (SR) at the end of one year. We conducted this study to see if outcomes of other trials are applicable in managed care setting. METHODS: We conducted a retrospective study in 370 consecutive patients who underwent ECV for AF. They were reviewed for initial outcome of ECV and recurrence of AF after a successful ECV, with and without prophylactic antiarrhythmic drugs. RESULTS: Initial success of ECV for AF was 65.7%. At one year, 47% remained in SR. AF for

Worsening of left ventricular end-systolic volume and mitral regurgitation without increase in left ventricular dyssynchrony on acute interruption of cardiac resynchronization therapy.

BACKGROUND: Responders to cardiac resynchronization therapy (CRT) have greater left ventricular (LV) dyssynchrony than nonresponders prior to CRT. AIM: We conducted this study to see whether the long term responders have more worsening of LV dyssynchrony and LV function on acute interruption of CRT. MATERIALS AND METHODS: We identified 22 responders and 13 nonresponders who received CRT as per standard criteria for 23.73 +/- 7.9 months (median 24.5 months). We assessed the acute change in LV function, mitral regurgitation (MR) and compared LV dyssynchrony in CRT on and off modes. RESULTS: On turning off CRT, there was no significant worsening of LV dyssynchrony in both responders and nonresponders. The dyssynchrony measurements by SPWMD, TDI and 3D echocardiography did not correlate significantly. LVESV increased (p = 0.02) and MR (p = 0.01) worsened in CRT-off mode in responders only without significant change in LVEF or LV dimensions. DISCUSSION AND CONCLUSION: In long-term responders to CRT, there is alteration in the function of remodeled LV with acute interruption of CRT, without significant worsening of LV dyssynchrony. The role of different echocardiographic parameters in the assessment of LV dyssynchrony remains controversial. Even after long-term CRT reversely remodels the LV, the therapy needs to be continued uninterrupted for sustained benefits.

Right ventricular dysfunction predicts poor outcome following hemodynamically compromising rejection.

BACKGROUND: Hemodynamically compromising rejection (HCR) is a major cause of mortality and morbidity after heart transplantation. Right ventricular (RV) function is a strong predictor of outcome in patients with heart failure and myocarditis. The objective of the current study is to determine whether RV dysfunction predicts event-free survival in patients with HCR. METHODS: Medical records of 548 heart transplant patients followed at Stanford University between January 1998 and January 2007 were reviewed. HCR was defined as a rejection episode requiring hospitalization for heart failure. Univariate and multivariate analyses were performed to identify risk factors for death or retransplantation at 1 year. RESULTS: HCR occurred in 71 patients (12.9%). Death or retransplantation at 1 year occurred in 28 patients (39%). Univariate analysis identified non-cellular rejection (odds ratio [OR] = 3.20, p = 0.021), the need for inotropic support (OR = 4.80, p = 0.007), RV dysfunction (OR = 4.63, p = 0.006), left ventricular ejection fraction (OR = 0.941, p = 0.031) and acute renal failure (OR = 3.82, p = 0.010) as predictors of death or retransplantation at 1 year. Multivariate analysis identified RV dysfunction (OR = 4.80, p = 0.007) and the need for inotropic support (OR = 5.00, p = 0.009) as predictors of death or retransplantation at 1 year. CONCLUSIONS: In the modern era of immunosuppression, HCR remains a major complication after heart transplantation. RV dysfunction was identified as a novel risk factor for death or retransplantation following HCR.

Multiplanar visualization in 3D transthoracic echocardiography for precise delineation of mitral valve pathology.

A novel multiplanar reformatting (MPR) technique in three-dimensional transthoracic echocardiography (3D TTE) was used to precisely localize the prolapsed lateral segment of posterior mitral valve leaflet in a patient symptomatic with mitral valve prolapse (MVP) and moderate mitral regurgitation (MR) before undergoing mitral valve repair surgery. Transesophageal echocardiography was avoided based on the findings of this new technique by 3D TTE. It was noninvasive, quick, reproducible and reliable. Also, it did not need the time-consuming reconstruction of multiple cardiac images. Mitral valve repair surgery was subsequently performed based on the MPR findings and corroborated the findings from the MPR examination.

Recurrence of iron deposition in the cardiac allograft in a patient with non-HFE hemochromatosis.

We report the case of a 36-year-old woman with a diagnosis of idiopathic dilated cardiomyopathy who underwent cardiac transplantation. The results of her initial iron studies were normal, but hemochromatosis was suspected after microscopy of the explanted heart revealed iron deposition. By 6 months post-transplantation, iron deposition was detected in her surveillance endomyocardial biopsy specimens and studies then confirmed the existence of non-HFE hemochromatosis. The patient has been stable on treatment with regular phlebotomies and a low vitamin C diet.