Impact of magnetic resonance imaging on functional integrity of non-conditional cardiovascular implantable electronic devices.

BACKGROUND: Cardiovascular implantable electronic devices (CIEDs) have historically restricted the use of magnetic resonance imaging (MRI) due to the potential clinical and configurational risks associated with electromagnetic interference. In this study, the authors investigated the impact of MRI on the functional integrity of non-conditional CIEDs and their clinical correlates. METHODS: In this prospective, observational single-center study, we enrolled patients undergoing MRI over a 5-year period. Prior to assessing the impact of MRI on CIEDs, we performed interrogations in sequential duplication to assess the intrinsic variability of devices. Subsequently, we performed interrogations immediately after MRI, and monitored changes in device parameters and clinical events. RESULTS: We completed 492 MRI studies, 58% in patients with permanent pacemakers (PPMs) and 42% with implantable cardioverter defibrillators (ICDs). Subsequent MRI exposures occurred in 15% encounters. Accounting for intrinsic variability in CIED leads, there were no significant changes in RA, RV, or LV parameters after MRI, regardless of the region imaged (thoracic vs. non-thoracic), type of CIED (PPMs vs. ICDs) and among those with serial MRIs. When ranked for % change pre- to post-MRI, the majority of RA, RV, and LV metrics for thresholds, sensing, and impedance conformed to ≤20% change from baseline. No significant clinical adverse cardiac events or effect on device microcircuitry occurred during the study. CONCLUSION: Incorporating a novel reproducibility tactic, there were neither clinically meaningful device parameter changes nor adverse clinical events during or following MRIs, suggesting the effects of MRI on non-conditional CIED integrity are far less than previously perceived.

Cardiovascular Magnetic Resonance Imaging-Incremental Value in a Series of 361 Patients Demonstrating Cost Savings and Clinical Benefits: An Outcome-Based Study.

BACKGROUND: This study was designed to assess the clinical impact and cost-benefit of cardiovascular magnetic resonance imaging (CMR). In the face of current health care cost concerns, cardiac imaging modalities have come under focused review. Data related to CMR clinical impact and cost-benefit are lacking. METHODS AND RESULTS: Retrospective review of 361 consecutive patients (pts) who underwent CMR exams was conducted. Indications for CMR were tabulated for appropriateness criteria. Components of the CMR exam were identified along with evidence of clinical impact. The cost of each CMR exam was ascertained along with cost savings attributable to the CMR exam for calculation of an incremental cost-effectiveness ratio. A total of 354 of 361 pts (98%) had diagnostic quality studies. Of the 361 pts, 350 (97%) had at least 1 published Appropriateness Criterion for CMR. A significant clinical impact attributable to CMR exam results was observed in 256 of 361 pts (71%). The CMR exam resulted in a new diagnosis in 69 of 361 (27%) pts. Cardiovascular magnetic resonance imaging results avoided invasive procedures in 38 (11%) pts and prevented additional diagnostic testing in 26 (7%) pts. Comparison of health care savings using CMR as opposed to current standards of care showed a net cost savings of $833 037, ie, per patient cost savings of $2308. CONCLUSIONS: Cardiovascular magnetic resonance imaging provides diagnostic image quality in >98% of cases. Cardiovascular magnetic resonance imaging findings have documentable clinical impact on patient management in 71% of pts undergoing the exam, in a cost beneficial manner.

Does Late Gadolinium Enhancement still have Value? Right Ventricular Internal Mechanical Work, Ea/Emax and Late Gadolinium Enhancement as Prognostic Markers in Patients with Advanced Pulmonary Hypertension via Cardiac MRI.

OBJECTIVES: Investigate the impact of Right Ventricular (RV) Internal Work (IW), ratio of arterial to ventricular end-systolic elastance (Ea/Emax), and RV Insertion Point (IP) Late Gadolinium Enhancement (LGE) on outcome in Pulmonary Hypertension (PH) patients. BACKGROUND: LGE is well known to be present within the RVIPs and Inter Ventricular Septum (IVS) in PH patients, but its prognostic role remains complex and potentially overestimated via 2D qualitative relative to the 3D quantitative measures now available. However, Ea/Emax, a measure of ventricular-arterial coupling and IW, when added to external cardiac work i.e. the P-V loop area as correlates to the heart's energy demands, might fundamentally improve measures of prognosis as they interrogate physiology beyond just the RV. METHODS: Cardiac Magnetic Resonance Imaging (CMR) of 124 PH patients (age = 60±13, 85F) referred to a large tertiary PH center, was retrospectively examined for RV volumetric and functional indices and RVIP LGE%. Right Heart Catheterizations (RHC) performed within 1±2 months of the CMR were reviewed. Ea/Emax was derived as RV End-Systolic Volume (ESV/RVSV). IW was estimated as RVESV ×(RV end-systolic pressure-RV diastolic pressure). Patients were followed from date of CMR for up to 5 years for MACE (death, hospitalized RV failure, initiation of parenteral prostacyclin, sustained ventricular arrhythmia or referral for lung transplantation). RESULTS: MACE was high; 48/124 (39%) patients had MACE by 1.6±1.3 years. Neither RVIP nor IVS LGE using visual assessment or even 3D quantization predicted MACE. The strongest predictor of MACE was RVIW (OR=1.00013, p<0.002), vs. mPAP, RV mass, RV EF and IP LGE. CONCLUSIONS: Surprisingly, neither a single time-point RVIP nor whole IVS LGE% can predict outcome in the largest cohort of PH patients studied to date when compared with conventional or contemporary metrics of disease progression. CMR-LGE appears to lose its' prognostic value in PH patients in stark contradistinction to all other left and right-sided human myocardial pathologies.

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.

BACKGROUND: CMR 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. METHODS: Over 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. RESULTS: Of 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. CONCLUSIONS: SSFP-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'.

Investigating cardiac MRI based right ventricular contractility as a novel non-invasive metric of pulmonary arterial pressure.

BACKGROUND: We test the hypothesis that cardiac magnetic resonance (CMR) imaging-based indices of four-dimensional (4D) (three dimensions (3D) + time) right ventricle (RV) function have predictive values in ascertaining invasive pulmonary arterial systolic pressure (PASP) measurements from right heart catheterization (RHC) in patients with pulmonary arterial hypertension (PAH). METHODS: We studied five patients with idiopathic PAH and two age and sex-matched controls for RV function using a novel contractility index (CI) for amplitude and phase to peak contraction established from analysis of regional shape variation in the RV endocardium over 20 cardiac phases, segmented from CMR images in multiple orientations. RESULTS: The amplitude of RV contractility correlated inversely with RV ejection fraction (RVEF; R (2) = 0.64, P = 0.03) and PASP (R (2) = 0.71, P = 0.02). Phase of peak RV contractility also correlated inversely to RVEF (R (2) = 0.499, P = 0.12) and PASP (R (2) = 0.66, P = 0.04). CONCLUSIONS: RV contractility analyzed from CMR offers promising non-invasive metrics for classification of PAH, which are congruent with invasive pressure measurements.

Left Ventricular Energy Model Predicts Adverse Events in Women With Suspected Myocardial Ischemia: Results From The NHLBI-Sponsored Women's Ischemia Syndrome Evaluation (WISE) Study.

OBJECTIVES: To assess the prognostic value of a left ventricular energy-model in women with suspected myocardial ischemia. BACKGROUND: The prognostic value of internal energy utilization (IEU) of the left ventricle in women with suspected myocardial ischemia is unknown. METHODS: Women (n=227, mean age 59±12 years, range 31-86), with symptoms of myocardial ischemia, underwent myocardial perfusion imaging (MPI) assessment for regional perfusion defects along with measurement of ventricular volumes separately by gated Single Photon Emission Computed Tomography (SPECT) (n= 207) and magnetic resonance imaging (MRI) (n=203). During follow-up (40±17 months), time to first major adverse cardiovascular event (MACE, death, myocardial infarction or hospitalization for congestive heart failure) was analyzed using MRI and gated SPECT variables. RESULTS: Adverse events occurred in 31 (14%). Multivariable Cox models were formed for each modality: IEU and wall thickness by MRI (Chi-squared 34, p<0.005) and IEU and systolic blood pressure by gated SEPCT (Chi-squared 34, p<0.005). The models remained predictive after adjustment for age, disease history and Framingham risk score. For each Cox model, patients were categorized as high-risk if the model hazard was positive and not high-risk otherwise. Kaplan-Meier analysis of time to MACE was performed for high-risk vs. not high-risk for MR (log rank 25.3, p<0.001) and gated SEPCT (log rank 18.2, p<001) models. CONCLUSIONS: Among women with suspected myocardial ischemia a high internal energy utilization has higher prognostic value than either a low EF or the presence of a myocardial perfusion defect assessed using two independent modalities of MR or gated SPECT.

Routine evaluation of left ventricular diastolic function by cardiovascular magnetic resonance: a practical approach.

BACKGROUND: Cardiovascular magnetic resonance (CMR) has excellent capabilities to assess ventricular systolic function. Current clinical scenarios warrant routine evaluation of ventricular diastolic function for complete evaluation, especially in congestive heart failure patients. To our knowledge, no systematic assessment of diastolic function over a range of lusitropy has been performed using CMR. METHODS AND RESULTS: Left ventricular diastolic function was assessed in 31 subjects (10 controls) who underwent CMR and compared with Transthoracic echocardiogram (TTE) evaluation of mitral valve (MV) and pulmonary vein (PV) blood flow. Blood flow in the MV and PV were successfully imaged by CMR for all cases (31/31,100%) while TTE evaluated flow in all MV (31/31,100%) but only 21/31 PV (68%) cases. Velocities of MV flow (E and A) measured by CMR correlated well with TTE (r = 0.81, p < 0.001), but demonstrated a systematic underestimation by CMR compared to TTE (slope = 0.77). Bland-Altman analysis of the E:A ratio and deceleration time (DT) calculated from each modality showed excellent agreement (bias -0.29, and -10.3 ms for E:A and DT, respectively). When assessing morphology using TTE, CMR correctly identified patients as having normal or abnormal inflow conditions. CONCLUSION: We have shown that there is homology between CMR and TTE for the assessment of diastolic inflow over a wide range of conditions, including normal, impaired relaxation and restrictive. There is excellent agreement of quantitative velocity measurements between CMR and TTE. Diastolic blood flow assessment by CMR can be performed in a single scan, with times ranging from 20 sec to 3 min, and we show that there is good indication for applying CMR to assess diastolic conditions, either as an adjunctive test when evaluating systolic function, or even as a primary test when TTE data cannot be obtained.

Traumatic Rupture of Atherosclerotic Plaque Producing Aortic Isthmus Dissection.

Traumatic rupture of aortic isthmus atherosclerotic plaque resulting in dissection has not been documented through the use of either invasive or noninvasive diagnostic modalities. We describe an elderly patient in whom transesophageal echocardiography and three-dimensional reconstruction of multiplane transesophageal two-dimensional images clearly demonstrated the traumatic dissection to be due to rupture of a large atherosclerotic plaque located in the aortic isthmus. The patient had experienced blunt trauma to the chest from the impact of the steering wheel during an automobile accident.