Assessing physician knowledge regarding indications for a primary prevention implantable defibrillator and potential barriers for referral

BACKGROUND

Although there is clear evidence to demonstrate that primary prevention implantable defibrillators (ICDs) reduce mortality in high-risk patients, ICDs are underutilized. Limited data exist assessing referring physicians' knowledge about guideline indications and attitudes towards ICDs, which may influence decision for referral.

METHODS AND RESULTS

The Arrhythmia Working Group from the Alberta Cardiovascular and Stroke Strategic Clinical Network developed a web-based survey consisting of case scenarios regarding primary prevention ICD indications and a list of barriers for referral to aid in the design of a complex device care pathway. We invited referring physicians to participate in the survey including internists and cardiologists and cardiology residents. The survey was completed by 109 of 799 (response rate = 14%) of physicians. Of those, 55% were internists, 32% cardiologists, and 13% cardiology residents. The majority of physicians were male (62%), practicing in a university hospital (66%). Overall, complete guideline-concordant answers were provided by 34% of physicians. In multivariable analysis, predictors of complete guideline concordance were being a cardiologist (odd ratio [OR] 5.9, confidence interval [CI] 2.1-16.4, P = 0.001) and cardiology resident (OR 6.7, CI 1.7-27.3, P = 0.007). The most common barrier for referral for internists was lack of confidence in knowledge of guideline recommendations; while cardiologists reported concerns about cost-effectiveness and cardiology residents were most concerned with inappropriate shocks.

CONCLUSION

Knowledge regarding indications for primary prevention ICD is limited and varies significantly among referring physicians. The barriers for referral differ among physician groups and addressing these identified barriers may help to improve appropriate ICD utilization.

Clinical feasibility and validation of 3D principal strain analysis from cine MRI: comparison to 2D strain by MRI and 3D speckle tracking echocardiography

Two-dimensional (2D) strain analysis is constrained by geometry-dependent reference directions of deformation (i.e. radial, circumferential, and longitudinal) following the assumption of cylindrical chamber architecture. Three-dimensional (3D) principal strain analysis may overcome such limitations by referencing intrinsic (i.e. principal) directions of deformation. This study aimed to demonstrate clinical feasibility of 3D principal strain analysis from routine 2D cine MRI with validation to strain from 2D tagged cine analysis and 3D speckle tracking echocardiography. Thirty-one patients undergoing cardiac MRI were studied. 3D strain was measured from routine, multi-planar 2D cine SSFP images using custom software designed to apply 4D deformation fields to 3D cardiac models to derive principal strain. Comparisons of strain estimates versus those by 2D tagged cine, 2D non-tagged cine (feature tracking), and 3D speckle tracking echocardiography (STE) were performed. Mean age was 51 ± 14 (36% female). Mean LV ejection fraction was 66 ± 10% (range 37–80%). 3D principal strain analysis was feasible in all subjects and showed high inter- and intra-observer reproducibility (ICC range 0.83–0.97 and 0.83–0.98, respectively—p < 0.001 for all directions). Strong correlations of minimum and maximum principal strain were respectively observed versus the following: 3D STE estimates of longitudinal (r = 0.81 and r = −0.64), circumferential (r = 0.76 and r = −0.58) and radial (r = −0.80 and r = 0.63) strain (p < 0.001 for all); 2D tagged cine estimates of longitudinal (r = 0.81 and r = −0.81), circumferential (r = 0.87 and r = −0.85), and radial (r = −0.76 and r = 0.81) strain (p < 0.0001 for all); and 2D cine (feature tracking) estimates of longitudinal (r = 0.85 and −0.83), circumferential (r = 0.88 and r = −0.87), and radial strain (r = −0.79 and r = 0.84, p < 0.0001 for all). 3D principal strain analysis is feasible using routine, multi-planar 2D cine MRI and shows high reproducibility with strong correlations to 2D conventional strain analysis and 3D STE-based analysis. Given its independence from geometry-related directions of deformation this technique may offer unique benefit for the detection and prognostication of myocardial disease, and warrants expanded investigation.

Abstract 157: Assessing Physician Knowledge Regarding Indications for a Primary Prevention Implantable Defibrillator and Potential Barriers for Referral

Background: Primary prevention implantable cardioverter defibrillators (ICD) are under-utilized despite multiple clinical trials that demonstrated reduced mortality and cost-effectiveness in patients at risk for sudden cardiac death. Our objectives were to determine physician knowledge about primary prevention ICD guidelines and to identify potential barriers impacting referral rates.

Methods: The Cardiovascular Arrhythmia and Stroke Working Group from Alberta, Canada developed a web- based survey as part of a quality assurance initiative to aid in the design of a complex device care pathway. The survey consisted of five case scenarios regarding primary prevention ICD guidelines and a list of potential barriers for ICD referral. Through expert consensus, case scenarios were developed based on current device guidelines. The survey was administered to physicians encountering patients eligible for ICD therapy, including General Internists and Cardiologists with Alberta Medical Association membership and Cardiology residents.

Results: The survey was completed by 109 of 799 (response rate =14%). Of those, 55% were General Internists, 32% were Cardiologists and 13% were Cardiology residents. The majority of physicians were male (62%) and practicing at a University Hospital (66%). Overall, 34% of participants answered all case scenarios correctly. A correct answer on all five case scenarios was demonstrated by 62.5% of Cardiologists, 61.5% of Cardiology residents and 16% of General Internists (p<0.0001). Figure 1 demonstrates significant differences regarding perceived barriers for ICD referral among physician groups (p<0.0001). There were also significant differences among physician age groups (p<0.0001), with younger physicians reporting more barriers. The most common barriers among all physician groups were cost- effectiveness (55%), concerns regarding knowledge of ICD guidelines (47%) and the risk of inappropriate shocks (41%).

Conclusion: Knowledge of indications for a primary prevention ICD is poor and a recognized barrier among physicians who may refer patients for device therapy. Adequate knowledge translation of ICD guidelines is crucial in order to improve ICD utilization.

The VITAH Trial-Vitamin D Supplementation and Cardiac Autonomic Tone in Patients with End-Stage Kidney Disease on Hemodialysis: A Blinded, Randomized Controlled Trial

End-stage kidney disease (ESKD) patients are at increased cardiovascular risk. Vitamin D deficiency is associated with depressed heart rate variability (HRV), a risk factor depicting poor cardiac autonomic tone and risk of cardiovascular death. Vitamin D deficiency and depressed HRV are highly prevalent in the ESKD population. We aimed to determine the effects of oral vitamin D supplementation on HRV ((low frequency (LF) to high frequency (HF) spectral ratio (LF:HF)) in ESKD patients on hemodialysis. Fifty-six subjects with ESKD requiring hemodialysis were recruited from January 2013–March 2015 and randomized 1:1 to either conventional (0.25 mcg alfacalcidol plus placebo 3×/week) or intensive (0.25 mcg alfacalcidol 3×/week plus 50,000 international units (IU) ergocalciferol 1×/week) vitamin D for six weeks. The primary outcome was the change in LF:HF. There was no difference in LF:HF from baseline to six weeks for either vitamin D treatment (conventional: p = 0.9 vs. baseline; intensive: p = 0.07 vs. baseline). However, participants who remained vitamin D-deficient (25-hydroxyvitamin D < 20 ng/mL) after treatment demonstrated an increase in LF:HF (conventional: n = 13, ∆LF:HF: 0.20 ± 0.06, p < 0.001 vs. insufficient and sufficient vitamin D groups; intensive: n = 8: ∆LF:HF: 0.15 ± 0.06, p < 0.001 vs. sufficient vitamin D group). Overall, six weeks of conventional or intensive vitamin D only augmented LF:HF in ESKD subjects who remained vitamin D-deficient after treatment. Our findings potentially suggest that while activated vitamin D, with or without additional nutritional vitamin D, does not appear to improve cardiac autonomic tone in hemodialysis patients with insufficient or sufficient baseline vitamin D levels, supplementation in patients with severe vitamin D deficiency may improve cardiac autonomic tone in this higher risk sub-population of ESKD. Trial Registration: ClinicalTrials.gov, NCT01774812.

Percutaneous Implantation of an Entirely Intracardiac Leadless Pacemaker

BACKGROUND

Cardiac pacemakers are limited by device-related complications, notably infection and problems related to pacemaker leads. We studied a miniaturized, fully self-contained leadless pacemaker that is nonsurgically implanted in the right ventricle with the use of a catheter.

METHODS

In this multicenter study, we implanted an active-fixation leadless cardiac pacemaker in patients who required permanent single-chamber ventricular pacing. The primary efficacy end point was both an acceptable pacing threshold (≤2.0 V at 0.4 msec) and an acceptable sensing amplitude (R wave ≥5.0 mV, or a value equal to or greater than the value at implantation) through 6 months. The primary safety end point was freedom from device-related serious adverse events through 6 months. In this ongoing study, the prespecified analysis of the primary end points was performed on data from the first 300 patients who completed 6 months of follow-up (primary cohort). The rates of the efficacy end point and safety end point were compared with performance goals (based on historical data) of 85% and 86%, respectively. Additional outcomes were assessed in all 526 patients who were enrolled as of June 2015 (the total cohort).

RESULTS

The leadless pacemaker was successfully implanted in 504 of the 526 patients in the total cohort (95.8%). The intention-to-treat primary efficacy end point was met in 270 of the 300 patients in the primary cohort (90.0%; 95% confidence interval [CI], 86.0 to 93.2, P=0.007), and the primary safety end point was met in 280 of the 300 patients (93.3%; 95% CI, 89.9 to 95.9; P<0.001). At 6 months, device-related serious adverse events were observed in 6.7% of the patients; events included device dislodgement with percutaneous retrieval (in 1.7%), cardiac perforation (in 1.3%), and pacing-threshold elevation requiring percutaneous retrieval and device replacement (in 1.3%).

CONCLUSIONS

The leadless cardiac pacemaker met prespecified pacing and sensing requirements in the large majority of patients. Device-related serious adverse events occurred in approximately 1 in 15 patients. (Funded by St. Jude Medical; LEADLESS II ClinicalTrials.gov number, NCT02030418.).

Heart Rate Turbulence and T-Wave Alternans in Patients with Coronary Artery Disease: The Influence of Diabetes

BACKGROUND

Patients with diabetes mellitus (DM) have a higher risk of sudden cardiac death. Factors associated with the risk profiles of coronary artery disease (CAD) patients with DM are not well established. Heart rate turbulence (HRT) and T-wave alternans (TWA) are often used to predict arrhythmia events.

METHODS AND RESULTS

HRT and TWA were measured in two independent groups: the ARTEMIS cohort study and the REFINE-ICD randomized trial. ARTEMIS assesses risk 3-12 months after coronary angiography in patients with CAD. The initial 1001 patients in ARTEMIS, 526 with and 475 without DM, are included in this analysis. REFINE-ICD compares usual care versus usual care plus ICD therapy in patients with left ventricular (LV) ejection fraction (EF) values of 36-50% assessed 2-15 months after myocardial infarction. The initial 275 patients screened in REFINE ICD are included in this analysis. Abnormal HRT plus TWA was more common in patients with versus without DM in ARTEMIS (125/526, 24% vs 63/475, 13%; P < 0.001) and REFINE-ICD (43/55, 78% vs 55/220, 25%; P < 0.001), respectively. Abnormal HRT plus TWA was also more common in patients with LVEF values < 50% (28%) vs ≥ 50% (18%; P < 0.001) in ARTEMIS and LVEF values below the population median of 42% (60/138, 43%) versus above the median (38/137, 28%; P < 0.01) in REFINE-ICD.

CONCLUSIONS

Abnormal HRT plus TWA is more common in CAD patients with DM compared with the patients without DM and is related to the severity of LV dysfunction.

CLINICAL TRIAL REGISTRATION INFORMATION

http://www.clinicaltrials.gov, NCT01426685; http://www.clinicaltrials.gov, NCT00673842.

Baseline Functional Class and Therapeutic Efficacy of Common Heart Failure Interventions: A Systematic Review and Meta-analysis

BACKGROUND

New York Heart Association (NYHA) functional class provides important prognostic information and is often used to select patients for cardiovascular therapies, yet, the effect of NYHA class on therapeutic efficacy has not been systematically studied.

METHODS

In this systematic review and meta-analysis we compared the relative and absolute mortality benefit of 5 common heart failure interventions (angiotensin-converting enzyme [ACE] inhibitors, β-blockers, mineralocorticoid receptor antagonists [MRAs], implantable cardioverter defibrillator [ICD], and cardiac resynchronization therapy [CRT]) across NYHA class. We included 26 randomized clinical trials of these interventions that reported all-cause mortality stratified according to baseline NYHA class in 36,406 patients.

RESULTS

Pooled relative risk for NYHA I/II vs. III/IV strata were similar for ACE inhibitors (0.90 vs. 0.88), β-blockers (0.72 vs. 0.79), MRA (0.79 vs. 0.75), and CRT (0.80 vs. 0.80), with all heterogeneity P > 0.8. Conversely, ICD efficacy was greater for class I/II (relative risk, 0.65 vs 0.86, heterogeneity P = 0.02). The pooled absolute risk difference was smaller for NYHA I/II vs III/IV with ACE inhibitors (-0.02 vs. -0.06, P = 0.12), β-blockers (-0.02 vs. -0.05, P = 0.047), MRA (-0.03 vs. -0.11, P = 0.001), and CRT (-0.01 vs. -0.04, P = 0.036), but was similar across NYHA class for the ICD (-0.07 vs. -0.05; P = 0.27).

CONCLUSIONS

Relative mortality reductions with most interventions were independent of baseline NYHA class. However, ICD efficacy was greater with NYHA I/II vs. III/IV limitation, and absolute benefit was greater with higher NYHA class. For interventions other than the ICD, there is little evidence supporting use of NYHA class as a rigid criterion for selecting heart failure therapies.

Phenotypic analysis of arrhythmogenic cardiomyopathy in the Hutterite population: role of electrocardiogram in identifying high-risk desmocollin-2 carriers

Background

The p.Gln554X mutation in desmocollin‐2 (DSC2) is prevalent in ≈10% of the Hutterite population. While the homozygous mutation causes severe biventricular arrhythmogenic right ventricular cardiomyopathy, the phenotypic features and prognosis of heterozygotes remain incompletely understood.

Methods and Results

Eleven homozygotes (mean age 32±8 years, 45% female), 28 heterozygotes (mean age 40±15 years, 50% female), and 22 mutation‐negatives (mean age 43±17 years, 41% female) were examined. Diagnostic testing was performed as per the arrhythmogenic right ventricular cardiomyopathy modified Task Force Criteria. Inverted T waves in the right precordial leads on ECG were seen in all homozygotes but not in their counterparts (P<0.001). Homozygotes had higher median daily premature ventricular complex burden than did heterozygotes or mutation‐negatives (1407 [IQR 1080 to 2936] versus 2 [IQR 0 to 6] versus 6 [IQR 0 to 214], P=0.0002). Ventricular tachycardia was observed in 60% of homozygotes but in none of the remaining individuals (P<0.001). On cardiac magnetic resonance imaging, homozygotes had significantly larger indexed end‐diastolic volumes (right ventricular: 122±24 versus 83±17 versus 83±12 mL/m², P<0.0001; left ventricular: 93±18 versus 76±13 versus 80±11 mL/m², P=0.0124) and lower ejection fraction values compared with heterozygotes and mutation‐negatives (right ventricular ejection fraction: 41±9% versus 59±9% versus 61±6%, P<0.0001; left ventricular ejection fraction: 53±8% versus 65±5% versus 64±5%, P<0.0001). Most affected individuals lacked right ventricular wall motion abnormalities. Thus, few met cardiac magnetic resonance imaging task force criteria.

Conclusions

The ECG reliably identifies homozygous p.Gln554X carriers and may be useful as an initial step in the screening of high‐risk Hutterites. The cardiac phenotype of heterozygotes appears benign, but further prospective follow‐up of their arrhythmic risk is needed.

Radiographic Predictors of Lead Conductor Fracture

Background—

Lead fracture is a limiting factor in high voltage lead durability. Fractures noted with the Medtronic Fidelis leads provide an opportunity to examine factors captured on implant chest x-ray that correlate with risk for lead conductor fracture. We evaluated contributory factors in a large population of fractures.

Methods and Results—

We conducted a retrospective case–control study at 8 Canadian centers that routinely capture anterior posterior and lateral chest x-rays within 2 weeks of implant. Cases were patients that experienced confirmed Medtronic Fidelis 6949 lead fracture based on standard definitions, matched one-to-one to controls for date of implant, sex, and age with normally functioning Fidelis leads from the same center. Select chart data and x-rays were collected for all patients. Radiographic measurements by ≥2 individuals per case/control were blinded to patient status. The data were analyzed using a time to failure multivariable Cox proportional hazards model with stratification for each matched pair. X-ray pairs from 111 fracture patients were compared with 111 controls (age 61.5±12.8 years, 75% male, 221 model 6949 leads). Six parameters included in the statistical analysis were significantly associated with risk of fracture, including slack/tortuosity measures, pulse generator and superior vena cava coil location, and angle of lead exit from the pocket.

Conclusions—

Pocket, intravascular and intracardiac lead characteristics on x-ray correlate with risk of lead conductor fracture. These observations may be useful to direct implant technique to optimize lead durability. Validation in larger populations and other lead models may inform the application of these results.

Getting by with less - the "frugal tie"

The ability to tie surgical knots efficiently and effectively is an essential surgical skill for medical procedures, especially pacemaker implantation. Device generators and their leads need to be safely anchored with sutures during implantation to prevent dislodgement and inadequate packaging in the pacemaker pocket. With most knot tying techniques, a generous amount of suture slack is required. We introduce a new technique that is a variation of the 2-handed surgical square knot and the 1-handed surgeon's knot that allows one to finish or tie a knot when left with little slack.

Incidence, predictors, and procedural results of upgrade to resynchronization therapy: the RAFT upgrade substudy

BACKGROUND

The resynchronization-defibrillation for ambulatory heart failure trial (RAFT) study demonstrated that adding cardiac resynchronization therapy (CRT) in selected patients requiring de novo implantable cardiac defibrillators (ICD) reduced mortality as compared with ICD therapy alone, despite an increase in procedure-related adverse events. Data are lacking regarding the management of patients with ICD therapy who develop an indication for CRT upgrade.

METHODS AND RESULTS

Participating RAFT centers provided data regarding de novo CRT-D (CRT with ICD) implant, upgrade to CRT-D during RAFT (study upgrade), and upgrade within 6 months after presentation of study results (substudy). Substudy centers enrolled 1346 (74.9%) patients in RAFT, including 644 de novo, 80 study upgrade, and 60 substudy CRT attempts. The success rate (initial plus repeat attempts) was 95.2% for de novo versus 96.3% for study upgrade and 90.0% for substudy CRT attempts (P=0.402). Acute complications occurred among 26.2% of de novo versus 18.8% of study upgrade and 3.4% of substudy CRT implantation attempts (P<0.001). The most common complication was left ventricular lead dislodgement. The principal reasons for not yet attempting upgrade in the substudy were patient preference (31.9%), New York Heart Association Class I (17.0%), and a QRS<150 ms (13.1%).

CONCLUSIONS

Among a broad group of implant physicians, CRT upgrades were performed in patients with an ICD in situ with no difference in implant success rate and a reduced acute complication rate as compared with a de novo CRT implant. Decisions to upgrade were influenced by predictors of benefit in subgroup analyses of the RAFT study and other trials.

The VITAH trial VITamin D supplementation and cardiac Autonomic tone in Hemodialysis: a blinded, randomized controlled trial

Background

Patients with end-stage kidney disease (ESKD) have a high rate of mortality and specifically an increased risk of sudden cardiac death (SCD). Impaired cardiac autonomic tone is associated with elevated risk of SCD. Moreover, patients with ESKD are often vitamin D deficient, which we have shown may be linked to autonomic dysfunction in humans. To date, it is not known whether vitamin D supplementation normalizes cardiac autonomic function in the high-risk ESKD population. The VITamin D supplementation and cardiac Autonomic tone in Hemodialysis (VITAH) randomized trial will determine whether intensive vitamin D supplementation therapies improve cardiac autonomic tone to a greater extent than conventional vitamin D supplementation regimens in ESKD patients requiring chronic hemodialysis.

Methods/Design

A total of 60 subjects with ESKD requiring thrice weekly chronic hemodialysis will be enrolled in this 2x2 crossover, blinded, randomized controlled trial. Following a 4-week washout period from any prior vitamin D therapy, subjects are randomized 1:1 to intensive versus standard vitamin D therapy for 6 weeks, followed by a 12-week washout period, and finally the remaining treatment arm for 6 weeks. Intensive vitamin D treatment includes alfacalcidiol (activated vitamin D) 0.25mcg orally with each dialysis session combined with ergocalciferol (nutritional vitamin D) 50 000 IU orally once per week and placebo the remaining two dialysis days for 6 weeks. The standard vitamin D treatment includes alfacalcidiol 0.25mcg orally combined with placebo each dialysis session per week for 6 weeks. Cardiac autonomic tone is measured via 24 h Holter monitor assessments on the first dialysis day of the week every 6 weeks throughout the study period. The primary outcome is change in the low frequency: high frequency heart rate variability (HRV) ratio during the first 12 h of the Holter recording at 6 weeks versus baseline. Secondary outcomes include additional measures of HRV. The safety of intensive versus conventional vitamin D supplementation is also assessed.

Discussion

VITAH will determine whether an intensive vitamin D supplementation regimen will improve cardiac autonomic tone compared to conventional vitamin D supplementation and will assess the safety of these two supplementation regimens in ESKD patients receiving chronic hemodialysis.

Trial registration

ClinicalTrials.gov, NCT01774812