Impact of the COVID-19 Pandemic on the Provision of Dialysis Service and Mortality in Veterans Receiving Maintenance Hemodialysis in the VA: An Interrupted Time-Series Analysis.

INTRODUCTION: According to the US Renal Data System (USRDS), patients with end-stage kidney disease (ESKD) on maintenance dialysis had higher mortality during early COVID-19 pandemic. Less is known about the effect of the pandemic on the delivery of outpatient maintenance hemodialysis and its impact on death. We examined the effect of pandemic-related disruption on the delivery of dialysis treatment and mortality in patients with ESKD receiving maintenance hemodialysis in the Veterans Health Administration (VHA) facilities, the largest integrated national healthcare system in the USA. METHODS: Using national VHA electronic health records data, we identified 7,302 Veterans with ESKD who received outpatient maintenance hemodialysis in VHA healthcare facilities during the COVID-19 pandemic (February 1, 2020, to December 31, 2021). We estimated the average change in the number of hemodialysis treatments received and deaths per 1,000 patients per month during the pandemic by conducting interrupted time-series analyses. We used seasonal autoregressive moving average (SARMA) models, in which February 2020 was used as the conditional intercept and months thereafter as conditional slope. The models were adjusted for seasonal variations and trends in rates during the pre-pandemic period (January 1, 2007, to January 31, 2020). RESULTS: The number (95% CI) of hemodialysis treatments received per 1,000 patients per month during the pre-pandemic and pandemic periods were 12,670 (12,525-12,796) and 12,865 (12,729-13,002), respectively. Respective all-cause mortality rates (95% CI) were 17.1 (16.7-17.5) and 19.6 (18.5-20.7) per 1,000 patients per month. Findings from SARMA models demonstrate that there was no reduction in the dialysis treatments delivered during the pandemic (rate ratio: 0.999; 95% CI: 0.998-1.001), but there was a 2.3% (95% CI: 1.5-3.1%) increase in mortality. During the pandemic, the non-COVID hospitalization rate was 146 (95% CI: 143-149) per 1,000 patients per month, which was lower than the pre-pandemic rate of 175 (95% CI: 173-176). In contrast, there was evidence of higher use of telephone encounters during the pandemic (3,023; 95% CI: 2,957-3,089), compared with the pre-pandemic rate (1,282; 95% CI: 1,241-1,324). CONCLUSIONS: We found no evidence that there was a disruption in the delivery of outpatient maintenance hemodialysis treatment in VHA facilities during the COVID-19 pandemic and that the modest rise in deaths during the pandemic is unlikely to be due to missed dialysis.

Artificial intelligence approaches for phenotyping heart failure in U.S. Veterans Health Administration electronic health record.

AIMS: Heart failure (HF) is a clinical syndrome with no definitive diagnostic tests. HF registries are often based on manual reviews of medical records of hospitalized HF patients identified using International Classification of Diseases (ICD) codes. However, most HF patients are not hospitalized, and manual review of big electronic health record (EHR) data is not practical. The US Department of Veterans Affairs (VA) has the largest integrated healthcare system in the nation, and an estimated 1.5 million patients have ICD codes for HF (HF ICD-code universe) in their VA EHR. The objective of our study was to develop artificial intelligence (AI) models to phenotype HF in these patients. METHODS AND RESULTS: The model development cohort (n = 20 000: training, 16 000; validation 2000; testing, 2000) included 10 000 patients with HF and 10 000 without HF who were matched by age, sex, race, inpatient/outpatient status, hospital, and encounter date (within 60 days). HF status was ascertained by manual chart reviews in VA's External Peer Review Program for HF (EPRP-HF) and non-HF status was ascertained by the absence of ICD codes for HF in VA EHR. Two clinicians annotated 1000 random snippets with HF-related keywords and labelled 436 as HF, which was then used to train and test a natural language processing (NLP) model to classify HF (positive predictive value or PPV, 0.81; sensitivity, 0.77). A machine learning (ML) model using linear support vector machine architecture was trained and tested to classify HF using EPRP-HF as cases (PPV, 0.86; sensitivity, 0.86). From the 'HF ICD-code universe', we randomly selected 200 patients (gold standard cohort) and two clinicians manually adjudicated HF (gold standard HF) in 145 of those patients by chart reviews. We calculated NLP, ML, and NLP + ML scores and used weighted F scores to derive their optimal threshold values for HF classification, which resulted in PPVs of 0.83, 0.77, and 0.85 and sensitivities of 0.86, 0.88, and 0.83, respectively. HF patients classified by the NLP + ML model were characteristically and prognostically similar to those with gold standard HF. All three models performed better than ICD code approaches: one principal hospital discharge diagnosis code for HF (PPV, 0.97; sensitivity, 0.21) or two primary outpatient encounter diagnosis codes for HF (PPV, 0.88; sensitivity, 0.54). CONCLUSIONS: These findings suggest that NLP and ML models are efficient AI tools to phenotype HF in big EHR data to create contemporary HF registries for clinical studies of effectiveness, quality improvement, and hypothesis generation.

Identification and outcomes of KDIGO-defined chronic kidney disease in 1.4 million U.S. Veterans with heart failure.

AIMS: According to the Kidney Disease: Improving Global Outcomes (KDIGO) guideline, the definition of chronic kidney disease (CKD) requires the presence of abnormal kidney structure or function for >3 months with implications for health. CKD in patients with heart failure (HF) has not been defined using this definition, and less is known about the true health implications of CKD in these patients. The objective of the current study was to identify patients with HF who met KDIGO criteria for CKD and examine their outcomes. METHODS AND RESULTS: Of the 1 419 729 Veterans with HF not receiving kidney replacement therapy, 828 744 had data on ≥2 ambulatory serum creatinine >90 days apart. CKD was defined as estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2 (n = 185 821) or urinary albumin-to-creatinine ratio (uACR) >30 mg/g (n = 32 730) present twice >3 months apart. Normal kidney function (NKF) was defined as eGFR ≥60 ml/min/1.73 m2, present for >3 months, without any uACR >30 mg/g (n = 365 963). Patients with eGFR <60 ml/min/1.73 m2 were categorized into four stages: 45-59 (n = 72 606), 30-44 (n = 74 812), 15-29 (n = 32 077), and <15 (n = 6326) ml/min/1.73 m2. Five-year all-cause mortality occurred in 40.4%, 57.8%, 65.6%, 73.3%, 69.7%, and 47.5% of patients with NKF, four eGFR stages, and uACR >30mg/g (albuminuria), respectively. Compared with NKF, hazard ratios (HR) (95% confidence intervals [CI]) for all-cause mortality associated with the four eGFR stages and albuminuria were 1.63 (1.62-1.65), 2.00 (1.98-2.02), 2.49 (2.45-2.52), 2.28 (2.21-2.35), and 1.22 (1.20-1.24), respectively. Respective age-adjusted HRs (95% CIs) were 1.13 (1.12-1.14), 1.36 (1.34-1.37), 1.87 (1.84-1.89), 2.24 (2.18-2.31) and 1.19 (1.17-1.21), and multivariable-adjusted HRs (95% CIs) were 1.11 (1.10-1.12), 1.24 (1.22-1.25), 1.46 (1.43-1.48), 1.42 (1.38-1.47), and 1.13 (1.11-1.16). Similar patterns were observed for associations with hospitalizations. CONCLUSION: Data needed to define CKD using KDIGO criteria were available in six out of ten patients, and CKD could be defined in seven out of ten patients with data. HF patients with KDIGO-defined CKD had higher risks for poor outcomes, most of which was not explained by abnormal kidney structure or function. Future studies need to examine whether CKD defined using a single eGFR is characteristically and prognostically different from CKD defined using KDIGO criteria.

Continuous EEG Characteristics in Critically ill Patients Presenting With Seizures Prior to Death From Cardiac Arrest.

Background: There have been limited reports about brain activity during cardiac arrest. Here we report 4 patients presenting with seizure who had cardiac arrest leading to their deaths while being on continuous video-EEG (cVEEG) monitoring and one-lead cardiac telemetry. Purpose: We illustrate characteristic stepwise EEG and EKG changes in these critically ill patients prior to their death. Research Design/Study Sample: All patients showed progressive broad spectrum of cardiac arrhythmias at or before the beginning of EEG suppression while there were no such changes seen in a control group of 4 randomly selected patients without cardiac arrest who had seizure on presentation and underwent cVEEG monitoring. Data Collection and Results: There was a progressive decline in EEG potentials associated with decreasing heart rate starting from the posterior region, more pronounced on the left, progressing to complete unilateral deactivation of the left fronto-central head regions while the right-sided networks became hyperactive before bilateral deactivation by the time of asystole. Conclusions: This case series provides a rare opportunity to compare EEG and EKG changes in patients who died while being on continuous EEG and EKG monitoring from hours to minutes prior to cardiac arrest and death.

Risk of Stroke in Older Adults With Heart Failure.

Heart failure (HF) is a risk factor for incident stroke. However, less is known about the independent nature of this association and to what extent various baseline characteristics may mediate this risk. Of the 5,795 community-dwelling adults aged ≥65 years in the Cardiovascular Health Study, 5,448 were free of baseline stroke, of whom 229 had baseline HF. We used a multivariable-adjusted Cox regression model to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for centrally adjudicated incident stroke associated with HF. Participants had a mean age of 73 years, 58% were women, and 15% were African-American. During 23 years of follow-up, incident stroke occurred in 18.8% and 19.3% of those with and without HF, respectively, but the time to first stroke was shorter in those with HF (age-gender-race-adjusted HR 1.64, 95% CI 1.21 to 2.25). The association remained essentially unchanged after adjustments for tobacco, alcohol, and physical activity (HR 1.63, 95% CI 1.21 to 2.24), attenuated after adjustment for hypertension, atrial fibrillation, myocardial infarction, and diabetes mellitus (HR 1.26, 95% CI 0.92 to 1.72), and further attenuated after additional adjustment for 10 baseline functional and subclinical variables (HR 1.05, 95% CI 0.76 to 1.46). In conclusion, despite a similar 23-year stroke incidence, time to first stroke was shorter in older adults with HF than without. However, this extra risk appears to be mediated primarily by 4 cardiovascular diseases that are also risk factors for HF. These findings highlight the importance of the primary prevention of these HF risk factors to reduce the extra risk of stroke in HF.

Imaging modality for left ventricular ejection fraction estimation and effect of implantable cardioverter-defibrillator on mortality in patients with heart failure.

BACKGROUND: Implantable cardioverter-defibrillators (ICDs) improve outcomes in patients with heart failure (HF) with left ventricular ejection fraction (LVEF) ≤35%. Less is known about whether outcomes varied between the 2 noninvasive imaging modalities used to estimate LVEF-2-dimensional echocardiography (2DE) and multigated acquisition radionuclide ventriculography (MUGA)-which use different principles (geometric vs count-based, respectively). OBJECTIVE: The purpose of this study was to examine whether the effect of ICD on mortality in patients with HF and LVEF ≤35% varied on the basis of LVEF measured by 2DE or MUGA. METHODS: Of the 2521 patients with HF with LVEF ≤35% in the Sudden Cardiac Death in Heart Failure Trial, 1676 (66%) were randomized to either placebo or ICD, of whom 1386 (83%) had LVEF measured by 2DE (n = 971) or MUGA (n = 415). Hazard ratios (HRs) and 97.5% confidence intervals (CIs) for mortality associated with ICD were estimated overall, checking for interaction, and within the 2 imaging subgroups. RESULTS: Of the 1386 patients in the present analysis, all-cause mortality occurred in 23.1% (160 of 692) and 29.7% (206 of 694) of patients randomized to ICD or placebo, respectively (HR 0.77; 97.5% CI 0.61-0.97), which is consistent with that in 1676 patients in the original report. HRs (97.5% CIs) for all-cause mortality in the 2DE and MUGA subgroups were 0.79 (0.60-1.04) and 0.72 (0.46-1.11), respectively (P = .693 for interaction). Similar associations were observed for cardiac and arrhythmic mortalities. CONCLUSION: We found no evidence that in patients with HF and LVEF ≤35%, the effect of ICD on mortality varied by the noninvasive imaging method used to measure LVEF.

Renin-Angiotensin Inhibition and Outcomes in HFrEF and Advanced Kidney Disease.

BACKGROUND: Renin-angiotensin system inhibitors improve outcomes in patients with heart failure with reduced ejection fraction (HFrEF). However, less is known about their effectiveness in patients with HFrEF and advanced kidney disease. METHODS: In the Medicare-linked Organized Program to Initiate Lifesaving Treatment in Hospitalized Patients with Heart Failure (OPTIMIZE-HF), 1582 patients with HFrEF (ejection fraction ≤40%) had advanced kidney disease (estimated glomerular filtration rate <30 mL/min/1.73 m2). Of these, 829 were not receiving angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) prior to admission, of whom 214 were initiated on these drugs prior to discharge. We calculated propensity scores for receipt of these drugs for each of the 829 patients and assembled a matched cohort of 388 patients, balanced on 47 baseline characteristics (mean age 78 years; 52% women; 10% African American; 73% receiving beta-blockers). Hazard ratios (HR) and 95% confidence intervals (CI) were estimated comparing 2-year outcomes in 194 patients initiated on ACE inhibitors or ARBs to 194 patients not initiated on those drugs. RESULTS: The combined endpoint of heart failure readmission or all-cause mortality occurred in 79% and 84% of patients initiated and not initiated on ACE inhibitors or ARBs, respectively (HR associated with initiation, 0.79; 95% CI, 0.63-0.98). Respective HRs (95% CI) for the individual endpoints of - Respective HRs (95% CI) for the individual endpoints of all-cause mortality and heart failure readmission were 0.81 (0.63-1.03) and 0.63 (0.47-0.85). CONCLUSIONS: The findings from our study add new information to the body of cumulative evidence that suggest that renin-angiotensin system inhibitors may improve clinical outcomes in patients with HFrEF and advanced kidney disease. These hypothesis-generating findings need to be replicated in contemporary patients.

Initiation of anti-hypertensive drugs and outcomes in patients with heart failure with preserved ejection fraction and persistent hypertension.

BACKGROUND: National heart failure (HF) guidelines recommend that in patients with HF with preserved ejection fraction (EF;HFpEF) and hypertension, systolic blood pressure (SBP) should be maintained below 130 mmHg. The objective of the study is to examine the association between initiation of anti-hypertensive drugs and outcomes in patients with HFpEF with persistent hypertension. METHODS: Of the 8873 hospitalized patients with HFpEF (EF ≥50%) with a history of hypertension without renal failure in Medicare-linked OPTIMIZE-HF, 3315 had a discharge SBP ≥130 mmHg, of whom 1971 were not receiving anti-hypertensive drugs, thiazides and calcium channel blockers, before hospitalization. Of these, 366 received discharge prescriptions for those drugs. We assembled a propensity score-matched cohort of 365 pairs of patients initiated and not initiated on anti-hypertensive drugs, balanced on 37 baseline characteristics. Hazard ratios (HR) and 95% confidence intervals (CI) for outcomes associated with anti-hypertensive drug initiation were estimated in the matched cohort. RESULTS: Matched patients (n = 730) had a mean age of 78 years; 67% were women and 17% African Americans. During 6 (median 2.5) years of follow-up, 66% of the patients died and 45% had HF readmission. HRs (95% CIs) for all-cause mortality at 30 days, 12 months and 6 years associated with anti-hypertensive drug initiation were 0.64 (0.30-1.36), 0.70 (0.51-0.97), and 0.95 (0.79-1.13), respectively. Respective HRs (95% CIs) for HF readmission were 1.65 (0.97-2.80), 1.18 (0.90-1.56) and 1.09 (0.88-1.35). CONCLUSIONS: Among hospitalized older patients with HFpEF with uncontrolled hypertension, the initiation of therapy with anti-hypertensive drugs was not associated with all-cause mortality or hospital readmission.

Initiation of Anti-Hypertensive Drugs and Outcomes in Patients with Heart Failure with Reduced Ejection Fraction.

BACKGROUND: In patients with heart failure with reduced ejection fraction (HFrEF) and hypertension, systolic blood pressure is recommended to be maintained below 130 mmHg, although this has not been shown to be associated with improved outcomes. We examined the association between anti-hypertensive drug initiation and outcomes in patients with HFrEF. METHODS: In the Medicare-linked OPTIMIZE-HF, 7966 patients with HFrEF (ejection fraction ≤40%) without renal failure were not receiving anti-hypertensive drugs before hospitalization, of whom 692 received discharge prescriptions for those drugs (thiazides and calcium channel blockers). We assembled a propensity score-matched cohort of 687 pairs of patients initiated and not initiated on anti-hypertensive drugs, balanced on 38 baseline characteristics. Hazard ratios (HR) and 95% confidence intervals (CIs) for outcomes associated with anti-hypertensive drug initiation were estimated in the matched cohort. RESULTS: Matched patients (n = 1374) had a mean age of 74 years, 41% were female, 17% were African-American, 66% were discharged on renin-angiotensin system inhibitors and beta blockers, and 10% on aldosterone antagonists. During 6 (median 2.5) years of follow-up, 70% of the patients died and 53% had heart failure readmission. Anti-hypertensive drug initiation was not significantly associated with all-cause mortality (HR, 0.95; 95% CI, 0.83-1.07) or heart failure readmission (HR, 0.93; 95% CI, 0.80-1.07). Similar associations were observed during 30 days and 12 months of follow-up. CONCLUSIONS: Among hospitalized older patients with HFrEF receiving contemporary treatments for heart failure, initiation of an anti-hypertensive drug was not associated with a lower risk of all-cause mortality or hospital readmission.

Limitations of closing percutaneous transthoracic ventricular access ports using a commercial collagen vascular closure device.

INTRODUCTION: Closed-chest access and closure of direct cardiac punctures may enable a range of therapeutic procedures. We evaluate the safety and feasibility of closing percutaneous direct ventricular access sites using a commercial collagen-based femoral artery closure device. METHODS: Yorkshire swine underwent percutaneous transthoracic left ventricular access (n = 13). The access port was closed using a commercial collagen-based vascular closure device (Angio-Seal, St. Jude Medical) with or without prior separation of the pericardial layers by instillation of fluid into the pericardial space ("permissive pericardial tamponade"). After initial nonsurvival feasibility experiments (n = 6); animals underwent 1-week (n = 3) or 6-week follow-up (n = 4). RESULTS: In naïve animals, the collagen plug tended to deploy outside the parietal pericardium, where it failed to accomplish hemostasis. "Permissive pericardial tamponade" was created under MRI, and accomplished early hemostasis by allowing the collagen sponge to seat on the epicardial surface inside the pericardium. After successful closure, six of seven animals accumulated a large pericardial effusion 5 ± 1 days after closure. Despite percutaneous drainage during 6-week follow-up, the large pericardial effusion recurred in half, and was lethal in one. CONCLUSIONS: A commercial collagen-based vascular closure device may achieve temporary but not durable hemostasis when closing a direct left ventricular puncture port, but only after intentional pericardial separation. These insights may contribute to development of a superior device solution. Elective clinical application of this device to close apical access ports should be avoided.

Real-time MR imaging-guided laser atrial septal puncture in swine.

PURPOSE: The authors performed this study to report their initial preclinical experience with real-time magnetic resonance (MR) imaging-guided atrial septal puncture by using a MR imaging-conspicuous blunt laser catheter that perforates only when energized. MATERIALS AND METHODS: The authors customized a 0.9-mm clinical excimer laser catheter with a receiver coil to impart MR imaging visibility at 1.5 T. Seven swine underwent laser transseptal puncture under real-time MR imaging. MR imaging signal-to-noise ratio profiles of the device were obtained in vitro. Tissue traversal force was tested with a calibrated meter. Position was corroborated with pressure measurements, oximetry, angiography, and necropsy. Intentional non-target perforation simulated serious complication. RESULTS: Embedded MR imaging antennae accurately reflected the position of the laser catheter tip and profile in vitro and in vivo. Despite having an increased profile from the microcoil, the 0.9-mm laser catheter traversed in vitro targets with similar force (0.22 N +/- 0.03) compared with the unmodified laser. Laser puncture of the atrial septum was successful and accurate in all animals. The laser was activated an average of 3.8 seconds +/- 0.4 before traversal. There were no sequelae after 6 hours of observation. Necropsy revealed 0.9-mm holes in the fossa ovalis in all animals. Intentional perforation of the aorta and atrial free wall was evident immediately. CONCLUSIONS: MR imaging-guided laser puncture of the interatrial septum is feasible in swine and offers controlled delivery of perforation energy by using an otherwise blunt catheter. Instantaneous soft tissue imaging provides immediate feedback on safety.

Interventional cardiovascular magnetic resonance imaging.

Magnetic resonance imaging provides structural and functional cardiovascular information with excellent soft tissue contrast. Real-time magnetic resonance imaging can guide transcatheter cardiovascular interventions in large animal models and may prove superior to x-ray and adjunct modalities for peripheral vascular, structural heart, and cardiac electrophysiology applications. We describe technical considerations, preclinical work, and early clinical studies in this emerging field.

Is statin therapy safe and effective in patients with chronic Kidney disease?

Chronic kidney disease (CKD) is associated with dyslipidemia and increased cardiovascular risk. This elevated risk for cardiovascular events exists even in the largest subpopulation with milder stages of CKD, prior to the development of significant reductions in renal excretory function. Statin therapy is a critical component of primary and secondary cardiovascular prevention efforts for at-risk patients. Efficacy in the CKD population, however, has appeared less robust across the spectrum of CKD, particularly in hemodialysis patients. This article will review the current state of knowledge on statin therapy in CKD, effects on renal outcomes, safety in this population and alternative lipid therapies.

Real-time magnetic resonance imaging-guided endovascular recanalization of chronic total arterial occlusion in a swine model.

BACKGROUND: Endovascular recanalization (guidewire traversal) of peripheral artery chronic total occlusion (CTO) can be challenging. X-ray angiography resolves CTO poorly. Virtually "blind" device advancement during x-ray-guided interventions can lead to procedure failure, perforation, and hemorrhage. Alternatively, MRI may delineate the artery within the occluded segment to enhance procedural safety and success. We hypothesized that real-time MRI (rtMRI)-guided CTO recanalization can be accomplished in an animal model. METHODS AND RESULTS: Carotid artery CTO was created by balloon injury in 19 lipid-overfed swine. After 6 to 8 weeks, 2 underwent direct necropsy analysis for histology, 3 underwent primary x-ray-guided CTO recanalization attempts, and the remaining 14 underwent rtMRI-guided recanalization attempts in a 1.5-T interventional MRI system. Real-time MRI intervention used custom CTO catheters and guidewires that incorporated MRI receiver antennae to enhance device visibility. The mean length of the occluded segments was 13.3+/-1.6 cm. The rtMRI-guided CTO recanalization was successful in 11 of 14 swine and in only 1 of 3 swine with the use of x-ray alone. After unsuccessful rtMRI (n=3), x-ray-guided attempts were also unsuccessful. CONCLUSIONS: Recanalization of long CTO is entirely feasible with the use of rtMRI guidance. Low-profile clinical-grade devices will be required to translate this experience to humans.

Renal Denervation Therapy for Drug-Resistant Hypertension: Does It Still Work?

OPINION STATEMENT: Hypertension is a global public health problem affecting one-fourth of the world's population. A subset of these patients with resistant hypertension presents a particular management problem and suffers a marked increase in cardiovascular risk. Treatment options have been limited, but the past decade has witnessed the emergence of catheter-based renal denervation to interrupt the sympathetic nervous system, long considered to play an important role in the development and maintenance of hypertension. Phase 1 and 2 studies reported remarkable reductions in blood pressure and sparked an excessive exuberance that ground to a halt with negative results of the SYMPLICITY HTN-3 pivotal trial. The subsequent and sober reappraisal has shed light on potential failure modes. Armed with appropriately cautious optimism, the field has resumed its move forward to realize the potential for therapeutic application in hypertension and other conditions characterized by sympathetic overactivity. This article summarizes the rich experimental data, early surgical experience, and available clinical trial results for catheter platforms. It concludes with discussion of knowledge gaps, lessons learned, and future directions.

Real-time magnetic resonance imaging-guided stenting of aortic coarctation with commercially available catheter devices in Swine.

BACKGROUND: Real-time MR imaging (rtMRI) is now technically capable of guiding catheter-based cardiovascular interventions. Compared with x-ray, rtMRI offers superior tissue imaging in any orientation without ionizing radiation. Translation to clinical trials has awaited the availability of clinical-grade catheter devices that are both MRI visible and safe. We report a preclinical safety and feasibility study of rtMRI-guided stenting in a porcine model of aortic coarctation using only commercially available catheter devices. METHOD AND RESULTS: Coarctation stenting was performed wholly under rtMRI guidance in 13 swine. rtMRI permitted procedure planning, device tracking, and accurate stent deployment. "Active" guidewires, incorporating MRI antennas, improved device visualization compared with unmodified "passive" nitinol guidewires and shortened procedure time (26+/-11 versus 106+/-42 minutes; P=0.008). Follow-up catheterization and necropsy showed accurate stent deployment, durable gradient reduction, and appropriate neointimal formation. MRI immediately identified aortic rupture when oversized devices were tested. CONCLUSIONS: This experience demonstrates preclinical safety and feasibility of rtMRI-guided aortic coarctation stenting using commercially available catheter devices. Patients may benefit from rtMRI in the future because of combined device and tissue imaging, freedom from ionizing radiation, and the ability to identify serious complications promptly.

Real-time magnetic resonance-guided endovascular repair of experimental abdominal aortic aneurysm in swine.

OBJECTIVES: This study tested the hypotheses that endografts can be visualized and navigated in vivo solely under real-time magnetic resonance imaging (rtMRI) guidance to repair experimental abdominal aortic aneurysms (AAA) in swine, and that MRI can provide immediate assessment of endograft apposition and aneurysm exclusion. BACKGROUND: Endovascular repair for AAA is limited by endoleak caused by inflow or outflow malapposition. The ability of rtMRI to image soft tissue and flow may improve on X-ray guidance of this procedure. METHODS: Infrarenal AAA was created in swine by balloon overstretch. We used one passive commercial endograft, imaged based on metal-induced MRI artifacts, and several types of homemade active endografts, incorporating MRI receiver coils (antennae). Custom interactive rtMRI features included color coding the catheter-antenna signals individually, simultaneous multislice imaging, and real-time three-dimensional rendering. RESULTS: Eleven repairs were performed solely using rtMRI, simultaneously depicting the device and soft-tissue pathology during endograft deployment. Active devices proved most useful. Intraprocedural MRI provided anatomic confirmation of stent strut apposition and functional corroboration of aneurysm exclusion and restoration of laminar flow in successful cases. In two cases, there was clear evidence of contrast accumulation in the aneurysm sac, denoting endoleak. CONCLUSIONS: Endovascular AAA repair is feasible under rtMRI guidance. Active endografts facilitate device visualization and complement the soft tissue contrast afforded by MRI for precise positioning and deployment. Magnetic resonance imaging also permits immediate post-procedural anatomic and functional evaluation of successful aneurysm exclusion.

Catheter-based endomyocardial injection with real-time magnetic resonance imaging.

BACKGROUND: We tested the feasibility of targeted left ventricular (LV) mural injection using real-time MRI (rtMRI). METHODS AND RESULTS: A 1.5T MRI scanner was customized with a fast reconstruction engine, transfemoral guiding catheter-receiver coil (GCC), MRI-compatible needle, and tableside consoles. Commercial real-time imaging software was customized to facilitate catheter navigation and visualization of injections at 4 completely refreshed frames per second. The aorta was traversed and the left ventricular cavity was entered under direct rtMRI guidance. Pigs underwent multiple injections with dilute gadolinium-DTPA. All myocardial segments were readily accessed. The active GCC and the passive Stiletto needle injector were readily visualized. More than 50 endomyocardial injections were performed with the aid of rtMRI; 81% were successful with this first-generation prototype. CONCLUSION: Percutaneous endomyocardial drug delivery is feasible with the aid of rtMRI, which permits precise 3-dimensional localization of injection within the LV wall.

Magnetic resonance fluoroscopy allows targeted delivery of mesenchymal stem cells to infarct borders in Swine.

BACKGROUND: The local environment of delivered mesenchymal stem cells (MSCs) may affect their ultimate phenotype. MR fluoroscopy has the potential to guide intramyocardial MSC injection to desirable targets, such as the border between infarcted and normal tissue. We tested the ability to (1) identify infarcts, (2) navigate injection catheters to preselected targets, (3) inject safely even into fresh infarcts, and (4) confirm injection success immediately. METHODS AND RESULTS: A 1.5-T MRI scanner was customized for interventional use, with rapid imaging, independent color highlighting of catheter channels, multiple-slice 3D rendering, catheter-only viewing mode, and infarct-enhanced imaging. MRI receiver coils were incorporated into guiding catheters and injection needles. These devices were tested for heating and used for targeted MSC delivery. In infarcted pigs, myocardium was targeted by MR fluoroscopy. Infarct-enhanced imaging included both saturation preparation MRI after intravenous gadolinium and wall motion. Porcine MSCs were MRI-labeled with iron-fluorescent particles. Catheter navigation and multiple cell injections were performed entirely with MR fluoroscopy at 8 frames/s with 1.7x3.3x8-mm voxels. Infarct-enhanced MR fluoroscopy permitted excellent delineation of infarct borders. All injections were safely and successfully delivered to their preselected targets, including infarct borders. Iron-fluorescent particle-labeled MSCs were readily visible on delivery in vivo and post mortem. CONCLUSIONS: Precise targeted delivery of potentially regenerative cellular treatments to recent myocardial infarction borders is feasible with an MR catheter delivery system. MR fluoroscopy permits visualization of catheter navigation, myocardial function, infarct borders, and labeled cells after injection.

Serial cardiac magnetic resonance imaging of injected mesenchymal stem cells.

BACKGROUND: Delivery and tracking of endomyocardial stem cells are limited by the inability to image transplanted cells noninvasively in the beating heart. We hypothesized that mesenchymal stem cells (MSCs) could be labeled with a iron fluorophore particle (IFP) to provide MRI contrast in vivo to assess immediate and long-term localization. METHODS AND RESULTS: MSCs were isolated from swine. Short-term incubation of MSCs with IFP resulted in dose-dependent and efficient labeling. Labeled cells remained viable for multiple passages and retained in vitro proliferation and differentiation capacity. Labeled MSCs (10(4) to 10(6) cells/150 microL) were injected percutaneously into normal and freshly infarcted myocardium in swine. One, 3, and 1 animals underwent serial cardiac MRI (1.5T) for 4, 8, and 21 days, respectively. MRI contrast properties were measured both in vivo and in vitro for cells embedded in agar. Injection sites containing as few as 10(5) MSCs could be detected and contained intact IFP-bearing MSCs on histology. CONCLUSIONS: IFP labeling of MSCs imparts useful MRI contrast, enabling ready detection in the beating heart on a conventional cardiac MR scanner after transplantation into normal and infarcted myocardium. The dual-labeled MSCs can be identified at locations corresponding to injection sites, both ex vivo using fluorescence microscopy and in vivo using susceptibility contrast on MRI. This technology may permit effective in vivo study of stem cell retention, engraftment, and migration.