Implantable cardioverter-defibrillators after myocardial infarction

Two-incision versus three-incision implantation technique of subcutaneous implantable cardioverter defibrillator: Systematic review and meta-analysis of 2076 patients

INTRODUCTION

The implantable cardioverter-defibrillator (ICD) was designed to detect and treat ventricular arrhythmias, which account for nearly half of all cardiovascular fatalities. Transvenous ICD (TV-ICD) complications were reduced by introducing subcutaneous ICD (S-ICD). S-ICD can be implanted using a three (3IT)- or two (2IT)-incision technique. This systematic review and meta-analysis was conducted to compare the 3IT to the 2IT.

METHODS

We searched medical electronic databases of Cochrane Central, Embase, PubMed, Scopus, and Web of Science (WOS) from the study's inception until March 8, 2023. We compared 2IT and 3IT techniques of S-ICDs in terms of procedural, safety, and efficacy outcomes. We used Review Manager software for the statistical analysis. We calculated the risk ratio (RR) with its 95% confidence interval (CI) for dichotomous variables; and the mean difference with its 95% CI for continuous variables. We measured the heterogeneity using the chi-squared and I-squared tests. If the data were heterogeneous, the random-effect (RE) model was applied; otherwise, the fixed-effect model (FE) was used.

RESULTS

We included three retrospective observational studies of 2076 patients, 1209 in the 2IT group and 867 in the 3IT. There was no statistically significant difference in erosion after S-ICD when 2IT compared with 3IT (RR = 0.27, 95% CI: [0.07, 1.02]; P = .05) (I2 = 0%, P = .90). There was no difference in risk of infection, lead dislocation, or inappropriate shock with either incision technique (RR = 0.78, 95% CI: [0.48, 1.29]; P = .34) (I2 = 0%, P = .71) and (RR = 0.37, 95% CI: [0.02, 8.14]; P = .53) (I2 = 66%, P = .05) respectively. Our meta-analysis showed that the efficacy of both techniques is comparable; Appropriate shock (RR = 0.94, 95% CI: [0.78, 1.12]; P = .48) (I2 = 0%, P = .81) and first shock efficacy (RR = 0.89, 95% CI: [0.44, 1.82]; P = .76) (I2 = 0%, P = .87).

CONCLUSION

2IT and 3IT of S-ICD have comparable efficacy and complication rates; however, the 3IT exposes patients to an additional incision without any additional benefits. These findings may provide clinicians with a simpler method for subcutaneous ICD implantation and likely result in improved cosmetic outcomes. Before the 2IT technique can be considered the standard of care, randomized controlled trials (RCTs) must be conducted to assess its long-term safety and efficacy.

Right Ventricular Function at Cardiac MRI Predicts Cardiovascular Events in Patients with an Implantable Cardioverter-Defibrillator

Background Right ventricular ejection fraction (RVEF) is an independent predictor of death and adverse cardiovascular outcomes in patients with various cardiac conditions. Purpose To investigate whether RVEF, measured with cardiac MRI, is a predictor of appropriate shock or death in implantable cardioverter-defibrillator (ICD) recipients for primary and secondary prevention of sudden cardiac death. Materials and Methods This retrospective, multicenter, observational study included patients who underwent cardiac MRI before ICD implantation between January 2007 and May 2017. Right ventricular end-diastolic and end-systolic volumes and RVEF were measured with cardiac MRI. The primary end point was a composite of all-cause mortality or appropriate ICD shock. The secondary end point was all-cause mortality. The association between RVEF and primary and secondary outcomes was evaluated by using multivariable Cox regression analysis. Potential interactions were tested between primary prevention, ischemic cause, left ventricular ejection fraction (LVEF), and RVEF. Results Among 411 patients (mean age ± standard deviation, 60 years; 315 men) during a median follow-up of 63 months, 143 (35%) patients experienced an appropriate ICD shock or died. In univariable analysis, lower RVEF was associated with greater risks for appropriate ICD shock or death and for death alone (log-rank trend test, P = .003 and .005 respectively). In multivariable Cox regression analysis adjusting for age at ICD implantation, LVEF, ICD indication (primary vs secondary), ischemic heart disease, and late gadolinium enhancement, RVEF was an independent predictor of the primary outcome (hazard ratio [HR], 1.21 per 10% lower RVEF; 95% CI: 1.04, 1.41; P = .01) and all-cause mortality (HR, 1.25 per 10% lower RVEF; 95% CI: 1.01, 1.55; P = .04). No evidence of significant interactions was found between RVEF and primary or secondary prevention (HR, 1.11 ± 0.17 [standard deviation]; P = .49), ischemic heart disease (HR, 1.02 ± 0.15; P = .78), and LVEF (HR, 0.91 ± 0.8; P = .29). Conclusion Right ventricular ejection fraction measured with cardiac MRI was a predictor of appropriate implantable cardioverter-defibrillator shock or death. © RSNA, 2021 See also the editorial by Nazarian and Zghaib in this issue.

Selvester score predicts implantable cardioverter defibrillator shocks in patients with non-ischemic cardiomyopathy

BACKGROUND

The implantable cardiac defibrillator is the cornerstone of prevention of sudden cardiac death in non-ischemic cardiomyopathy. The Selvester score, which is frequently investigated in ischemic cardiomyopathy, has not been investigated in the field of non-ischemic cardiomyopathy.

AIM

The aim of this study was to evaluate the Selvester score for determining appropriate implantable cardiac defibrillator shocks in non-ischemic cardiomyopathy patients.

MATERIALS AND METHODS

In all, 131 non-ischemic cardiomyopathy patients were included in the study. A simplified Selvester score was calculated from ECG data. Patients were divided into two groups according to whether they received ICD shock.

RESULTS

Of the patients, 28.2% received appropriate implantable cardiac defibrillator shock. The Selvester score was significantly higher in patients receiving appropriate shock when compared to patients with no implantable cardiac defibrillator shocks (8.8 ± 4.6 vs 7.2 ± 3.3, P = .040). The median QRS duration was significantly longer in patients receiving appropriate shock than in patients with no shocks (130.14 ± 35.08 ms vs 120.12 ± 20.57 ms, P = .045). We determined that the cutoff value for the Selvester score to predict ICD shocks was 6.5 with a sensitivity of 72.0% and a specificity of 83% (AUC = 0.717; %95 GA: 0.627-0.807, P < .001).

CONCLUSION

Selvester score was higher in patients receiving appropriate shock than in patients who did not receive any implantable cardiac defibrillator shock. From this study, the Selvester score is associated with the risk of ventricular tachycardia/ventricular fibrillation in non-ischemic cardiomyopathy so that careful attention is necessary to manage the patients with high Selvester score.

Detection of Ventricular Fibrillation Based on Ballistocardiography by Constructing an Effective Feature Set

Ventricular fibrillation (VF) is a type of fatal arrhythmia that can cause sudden death within minutes. The study of a VF detection algorithm has important clinical significance. This study aimed to develop an algorithm for the automatic detection of VF based on the acquisition of cardiac mechanical activity-related signals, namely ballistocardiography (BCG), by non-contact sensors. BCG signals, including VF, sinus rhythm, and motion artifacts, were collected through electric defibrillation experiments in pigs. Through autocorrelation and S transform, the time-frequency graph with obvious information of cardiac rhythmic activity was obtained, and a feature set of 13 elements was constructed for each 7 s segment after statistical analysis and hierarchical clustering. Then, the random forest classifier was used to classify VF and non-VF, and two paradigms of intra-patient and inter-patient were used to evaluate the performance. The results showed that the sensitivity and specificity were 0.965 and 0.958 under 10-fold cross-validation, and they were 0.947 and 0.946 under leave-one-subject-out cross-validation. In conclusion, the proposed algorithm combining feature extraction and machine learning can effectively detect VF in BCG, laying a foundation for the development of long-term self-cardiac monitoring at home and a VF real-time detection and alarm system.

Arrhythmic event prediction in patients with heart failure and reduced ejection fraction

AIMS

Implantable cardioverter defibrillator (ICD) is an effective treatment to reduce mortality in patients with symptomatic heart failure and left ventricular ejection fraction (LVEF) 35% or less. LVEF presents a low sensitivity for predicting arrhythmic events. Aim of this study was to identify predictors of sustained ventricular arrhythmias (SVAs), overall and according to the cause of heart failure.

METHODS

Single-center, retrospective, cohort study of 193 patients (51 nonischemic and 142 ischemic) with chronic heart failure and LVEF less than 35% who had received ICD for primary prevention of sudden cardiac death. We collected clinical data, echocardiographic parameters and SVAs detected by the ICD.

RESULTS

During a median follow-up of 1440 days, 32 (16.2%) patients had SVAs. SVAs incidence was similar in patients with nonischemic (15.6%) and ischemic cause of heart failure (16.9%). Hypertension, diabetes, chronic renal failure, atrial fibrillation, chronic obstructive pulmonary disease, New York Heart Association class at least III were predictors at univariate analysis of SVAs. A clinical score, assigning one point to each of these variables, was associated with a significantly increased risk of SVAs [odds ratio for each point increase = 1.92, 95% confidence interval 1.40-2.65, P < 0.0001, area under the curve (AUC) 0.73], with 72% sensitivity and 60% specificity for a cutoff at least three and remained significant in nonischemic (AUC 0.84) and ischemic (AUC 0.68) patients.

CONCLUSION

Our study shows the benefit of ICD implantation in primary prevention and its independency of cause. A simple clinical score, based on comorbidities, identifies patients with more benefits from ICD implantation.

Salvage of Exposed Cardiac Implants Using Fasciocutaneous Rotation Flaps

INTRODUCTION

Implantation rates of cardiac implantable electrophysiological devices (CIEDs) are rising, mainly because of the expansion of implantable cardioverter-defibrillators indications for primary prevention. As the CIED usage increases, CIED-related complications are also in rise. Transvenous approach and laser utilization techniques are replacing the open heart surgeries, for removal of CIED systems that are suspected to be infected. In this study, we aimed to share our new method of fasciocutaneous flap coverage results of patients with exposed CIED systems who were not eligible for the CIED replacement surgery for various reasons.

PATIENTS AND METHODS

Patients operated with rotational fasciocutaneous flaps with addition of pectoralis fascia, owing to their exposed CIEDs between June 2016 and January 2019, were enlisted. Patients with signs of infection whether systemic or limited to the CIED pocket with or without positive blood cultures were referred to infectious diseases department and not included in this study. Patients included in the study were evaluated retrospectively in terms of demographic data, implanted CIED type, time elapsed from implantation to exposure, from referral to flap coverage operation, total follow-up time, survival ratios during follow-up, and complications related to flap coverage operation. In addition, indications for CIED implantation, patient comorbidities, and culture results obtained from the capsule encompassing the CIED battery unit were included to the evaluation.

RESULTS

A total of 13 patients with exposed CIEDs have undergone total capsulectomy and CIED system coverage with rotational fasciocutaneous flaps. The mean patient age ± SD was 60.2 ± 13.4 years. The average time elapsed from CIED implantation to exposure was 27.3 ± 15.4 months. The average time spanned from initial referral to operation was 6 ± 1.6 days. The most prevalent comorbidity was diabetes mellitus. The average time elapsed during operation for pectoral fascia incorporated rotation flaps was 90 ± 10.6 minutes. Coagulase negative staphylococci were the dominant species (46.5%) obtained from capsule cultures. Apart from 1 case of hematoma, no early or late operation-related complication was encountered.

CONCLUSIONS

A more precise definition of contamination and infection has to be made in guidelines, which may lead the first group to be treated without extraction. Surgical method defined in this study can be used for the treatment of patients in contaminated CIED subgroup, conserving individuals from risks of device extraction.

Multi-contrast volumetric imaging with isotropic resolution for assessing infarct heterogeneity: Initial clinical experience

BACKGROUND

To evaluate accelerated multi-contrast volumetric imaging with isotropic resolution reconstructed using low-rank and spatially varying edge-preserving constrained compressed sensing parallel imaging reconstruction (CP-LASER), for assessing infarct heterogeneity on post-infarction patients as a precursor to studies of utility for predicting ventricular arrhythmias.

METHODS

Eleven patients with prior myocardial infarction were included in the study. All subjects underwent cardiovascular magnetic resonance (CMR) scans including conventional two-dimensional late gadolinium enhancement (2D LGE) and three-dimensional multi-contrast late enhancement (3D MCLE) post-contrast. The extent of the infarct core and peri-infarct gray zone of a limited mid-ventricular slab were derived respectively by analyzing MCLE images with an isotropic resolution of 2.2 mm and an anisotropic resolution of 2.2×2.2×8.8 mm 3 , and LGE images with a resolution of 1.37×2.7×8 mm 3 ; the respective measures across all subjects were statistically compared.

RESULTS

Using 3D MCLE, the infarct core size measured with isotropic resolution was similar to that measured with anisotropic resolution, while the peri-infarct gray zone size measured with isotropic resolution was smaller than that measured with anisotropic resolution ( p<0.001 , Cohen's dz=1.33 ). Isotropic 3D MCLE yielded a significantly smaller measure of the peri-infarct gray zone size than conventional 2D LGE ( p=0.0016 , Cohen's dz=1.20 ). Overall, we have successfully shown the utility of isotropic 3D MCLE in a pilot patient study. Our results suggest that smaller voxels lead to more accurate differentiation between isotropic 3D MCLE-derived gray zone and core infarct because of diminished partial volume effect.

CONCLUSION

The CP-LASER accelerated 3D MCLE with isotropic resolution can be used in patients and yields excellent delineation of infarct and peri-infarct gray zone characteristics.

Heart Rate Variability Analysis to Predict Onset of Ventricular Tachyarrhythmias in Implantable Cardioverter Defibrillators

Implantable cardioverter defibrillators (ICDs) are commonly used in patients at high risk of sudden cardiac death (SCD) to help prevent and treat life-threatening arrhythmia. Up to 80% of cases of sudden cardiac death are caused by ventricular tachyarrhythmias (VTA) and the accurate prediction of VTA in patients with ICDs can help prevent SCD. Early prediction allows tiered and less invasive therapies to be used to help prevent VTA which are more easily tolerated by the patient and are less battery intensive. In this work, a comparative study of three types of frequency domain features (spectral, bispectrum, and Fourier-Bessel) for VTA prediction is presented based on heart rate variability (HRV) signals between one and five minutes prior to known SCD. Using Fourier-Bessel features and a standard classification approach resulted in the best performance of 87.5% accuracy, 89.3% sensitivity and 85.7% specificity. These results suggest that Fourier-Bessel features are a promising approach for SCD prediction, and that new feature development can help improve both the sensitivity and specificity of SCD prediction in ICDs.

Prediction of Sudden Cardiac Death in Implantable Cardioverter Defibrillators: A Review and Comparative Study of Heart Rate Variability Features

Over the last four decades, implantable cardioverter defibrillators (ICDs) have been widely deployed to reduce sudden cardiac death (SCD) risk in patients with a history of life-threatening arrhythmia. By continuous monitoring of the heart rate, ICDs can use decision algorithms to distinguish normal cardiac sinus rhythm or supra-ventricular tachycardia from abnormal cardiac rhythms like ventricular tachycardia and ventricular fibrillation and deliver appropriate therapy such as an electrical stimulus. Despite the success of ICDs, more research is still needed, particularly in decision-making algorithms. Because of low specificity in practical devices, patients with ICDs still receive inappropriate shocks, which may lead to inadvertent mortality and reduction of quality of life. At the same time, higher sensitivity can lead to the use of newer tiered therapies. The purpose of this study is to review the literature on common signal features used in detection algorithms for abnormal cardiac sinus rhythm, as well as reviewing datasets used for algorithm development in previous studies. More than 50 different features to address heart rate changes before SCD have been reviewed and general methodology on this area proposed based on variety of studies on ICDs functionality. A comparative study on the prediction performance of these features, using a common database, is also presented. By combining these features with a support vector machine classifier, achieved results have compared well with other studies.

Optimal method of measuring the T-peak to T-end interval for risk stratification in primary prevention

Aims

Several published investigations demonstrated that a longer T-peak to T-end interval (Tpe) implies increased risk for ventricular tachyarrhythmia (VT/VF) and mortality. Tpe has been measured using diverse methods. We aimed to determine the optimal Tpe measurement method for screening purposes.

Methods and results

We evaluated 305 patients with LVEF ≤ 35% and an implantable cardioverter-defibrillator implanted for primary prevention. Tpe was measured using seven different methods described in the literature, including six manual methods and the automated algorithm '12SL', and was corrected for heart rate. Endpoints were VT/VF and death. To account for differences in the magnitude of Tpe measurements, results are expressed in standard deviation (SD) increments. We evaluated the clinical utility of each measurement method based on predictive ability, fraction of immeasurable tracings, and intra- and interobserver correlation. >Over 31 ± 23 months, 82 (27%) patients had VT/VF, and over 49 ± 21 months, 91 (30%) died. Several rate-corrected Tpe measurement methods predicted VT/VF (HR per SD 1.20-1.34; all P < 0.05), and nearly all methods (both corrected and uncorrected) predicted death (HR per SD 1.19-1.35; all P < 0.05). Optimal predictive ability, readability, and correlation were found in the automated 12SL method and the manual tangent method in lead V2.

Conclusion

For the prediction of VT/VF, the utility of Tpe depends upon the measurement method, but for the prediction of mortality, most published Tpe measurement methods are similarly predictive. Heart rate correction improves predictive ability. The automated 12SL method performs as well as any manual measurement, and among manual methods, lead V2 is most useful.

Electrophysiology testing for risk stratification of patients with ischaemic cardiomyopathy: a call for action

Current guidelines recommendations, based on the results of primary sudden cardiac death prevention trials, use the left ventricular ejection fraction (LVEF) as a sole criterion for the indication of implantable cardioverter defibrillator therapy for primary prevention purposes. In this article, we review the sensitivity and specificity of LVEF for predicting arrhythmic vs. non-arrhythmic cardiac death and examine existing evidence on the use of electrophysiology testing for risk stratification of ischaemic patients with reduced left ventricular function.

Prolonged Ventricular Conduction and Repolarization During Right Ventricular Stimulation Predicts Ventricular Arrhythmias and Death in Patients With Cardiomyopathy

OBJECTIVES

The goal of this study was to evaluate whether prolonged ventricular conduction (paced QRS) and repolarization (paced QTc) times observed during ventricular stimulation predict ventricular arrhythmic events and death.

BACKGROUND

Abnormal ventricular conduction and repolarization can predispose patients to ventricular arrhythmias.

METHODS

Consecutive patients with left ventricular dysfunction (ejection fraction <50%) undergoing electrophysiology studies from January 2002 until May 2014 were identified at Mayo Clinic (Rochester, Minnesota). Patients were followed up until December 2014 for occurrence of ventricular arrhythmias and death.

RESULTS

Among the 501 patients included (mean age 65 years; mean left ventricular ejection fraction 33.1%), longer paced ventricular conduction was associated with longer baseline QRS duration, longer QT interval, and lower ejection fraction. On multivariable analysis, longer paced QRS duration was associated with higher risk of ventricular arrhythmia (hazard ratio [HR]: 1.11 per 10-ms increase; 95% confidence interval [CI]: 1.07 to 1.16; p < 0.001) and all-cause death or arrhythmia (HR: 1.09; 95% CI: 1.09 to 1.13; p < 0.001). A paced QRS duration >190 ms was associated with a 3.6 times higher risk of ventricular arrhythmia (HR: 3.6; 95% CI: 2.35 to 5.53; p < 0.001) and a 2.1 times higher risk of death or arrhythmia (HR: 2.12; 95% CI: 1.53 to 2.95; p < 0.001), independent of left ventricular function or baseline QRS duration. Longer QTc interval during ventricular pacing was associated with a higher risk of ventricular arrhythmia (HR: 1.03 per 10-ms increase; 95% CI: 1.02 to 1.12; p < 0.001) independent of paced QRS duration.

CONCLUSIONS

Longer paced QRS duration and paced QTc interval predict ventricular arrhythmias in patients with cardiomyopathy. Ventricular conduction and repolarization prolongation during right ventricular pacing can determine the risk of ventricular arrhythmias.

Causes of Death in a Contemporary Cohort of Patients With Type 2 Diabetes and Atherosclerotic Cardiovascular Disease: Insights From the TECOS Trial

OBJECTIVE

We evaluated the specific causes of death and their associated risk factors in a contemporary cohort of patients with type 2 diabetes and atherosclerotic cardiovascular disease (ASCVD).

RESEARCH DESIGN AND METHODS

We used data from the Trial Evaluating Cardiovascular Outcomes with Sitagliptin (TECOS) study (n = 14,671), a cardiovascular (CV) safety trial adding sitagliptin versus placebo to usual care in patients with type 2 diabetes and ASCVD (median follow-up 3 years). An independent committee blinded to treatment assignment adjudicated each cause of death. Cox proportional hazards models were used to identify risk factors associated with each outcome.

RESULTS

A total of 1,084 deaths were adjudicated as the following: 530 CV (1.2/100 patient-years [PY], 49% of deaths), 338 non-CV (0.77/100 PY, 31% of deaths), and 216 unknown (0.49/100 PY, 20% of deaths). The most common CV death was sudden death (n = 145, 27% of CV death) followed by acute myocardial infarction (MI)/stroke (n = 113 [MI n = 48, stroke n = 65], 21% of CV death) and heart failure (HF) (n = 63, 12% of CV death). The most common non-CV death was malignancy (n = 154, 46% of non-CV death). The risk of specific CV death subcategories was lower among patients with no baseline history of HF, including sudden death (hazard ratio [HR] 0.4; P = 0.0036), MI/stroke death (HR 0.47; P = 0.049), and HF death (HR 0.29; P = 0.0057).

CONCLUSIONS

In this analysis of a contemporary cohort of patients with diabetes and ASCVD, sudden death was the most common subcategory of CV death. HF prevention may represent an avenue to reduce the risk of specific CV death subcategories.

Current Clinical Applications and Next Steps for Cardiac Innervation Imaging

PURPOSE OF REVIEW

Autonomic innervation is crucial for regulating cardiac function. Sympathetic innervation imaging with ¹²³I-mIBG and analogous PET tracers assesses disease in ways that differ from customary methods. This review describes practical use in various clinical scenarios, discusses recent guidelines, presents new data confirming risk stratification power, describes an ongoing prospective study, and looks forward to wider use in patient management.

RECENT FINDINGS

ASNC ¹²³I-mIBG guidelines are available, expanding on European guidelines. ADMIRE-HF patient follow-up increased to 2 years in ADMIRE HFX, demonstrating independent mortality risk reclassification. ADMIRE-HF findings were substantiated in a Japanese consortium study and in the PAREPET ¹¹C-HED PET study. Exciting potential uses of adrenergic imaging are management of LVADs and VT ablation. CZT cameras provide advantages, but derived parameters differ from Anger camera values. Independent risk stratification utility of adrenergic imaging with ¹²³I-mIBG and PET tracers is continuously being confirmed. An ongoing prospective randomized study promises to establish patient management utility. There is potential for wider use and improved images with newer cameras and PET.

Biomarker-based diagnosis of pacemaker and implantable cardioverter defibrillator pocket infections: A prospective, multicentre, case-control evaluation

Background

The use of cardiac implantable electronic devices (CIED) has risen steadily, yet the rate of cardiac device infections (CDI) has disproportionately increased. Amongst all cardiac device infections, the pocket infection is the most challenging diagnosis. Therefore, we aimed to improve diagnosis of such pocket infection by identifying relevant biomarkers.

Methods

We enrolled 25 consecutive patients with invasively and microbiologically confirmed pocket infection. None of the patients had any confounding conditions. Pre-operative levels of 14 biomarkers were compared in infected and control (n = 50) patients. Our selected biomarkers included white blood cell count (WBC), C-reactive protein (CRP), procalcitonin (PCT), lipopolysaccharide binding protein, high-sensitivity C-reactive protein (HS-CRP), polymorphonuclear-elastase, presepsin, various interleukins, tumor necrosis factor α (TNF-α), and granulocyte macrophage colony-stimulating factor (GM-CSF).

Results

Of the 25 patients with isolated pocket infection (70±13years, 76% male, 40% ICDs), none presented with leukocytosis. In contrast, they had higher serum levels of HS-CRP (p = 0.019) and PCT (p = 0.010) than control patients. Median PCT-level was 0.06 ng/mL (IQR 0.03–0.07 ng/mL) in the study group versus 0.03 ng/mL (IQR 0.02–0.04 ng/mL) in controls. An optimized PCT cut-off value of 0.05 ng/mL suggests pocket infection with a sensitivity of 60% and specificity of 82%. In addition TNF-α- and GM-CSF-levels were lower in the study group. Other biomarkers did not differ between groups.

Conclusion

Diagnosis of isolated pocket infections requires clinical awareness, physical examination, evaluation of blood cultures and echocardiography assessment. Nevertheless, measurement of PCT- and HS-CRP-levels can aid diagnosis. However, no conclusion can be drawn from normal WBC-values.

Clinical trial registration

clinicaltrials.gov identifier: NCT01619267

Mechanisms of sudden cardiac death

Sudden cardiac death (SCD) continues to be a major public health problem and is thought to account for almost half of all cardiac deaths. Cardiac arrest and SCD are most commonly due to ventricular arrhythmias. Most patients who suffer cardiac arrest have underlying structural heart disease, with coronary artery disease (CAD) being the most common. In the setting of CAD, ventricular arrhythmias can result due to acute ischemia in the absence of preexisting myocardial scarring or in the presence of established scar from prior infarction without clinically significant ischemia. LV systolic dysfunction is an important predictor of risk for SCD in ischemic heart disease and in most nonischemic disorders, although other factors such as ventricular hypertrophy also play a role. Cardiac arrest and SCD can also occur due to primary electrical disorders in the absence of major structural abnormalities.

Relationship between right and left ventricular function in candidates for implantable cardioverter defibrillator with low left ventricular ejection fraction

Background

Indications for the primary prevention of sudden death using an implantable cardioverter defibrillator (ICD) are based predominantly on left ventricular ejection fraction (LVEF). However, right ventricular ejection fraction (RVEF) is also a known prognostic factor in a variety of structural heart diseases that predispose to sudden cardiac death. We sought to investigate the relationship between right and left ventricular parameters (function and volume) measured by cardiovascular magnetic resonance (CMR) among a broad spectrum of patients considered for an ICD.

Methods

In this retrospective, single tertiary-care center study, consecutive patients considered for ICD implantation who were referred for LVEF assessment by CMR were included. Right and left ventricular function and volumes were measured.

Results

In total, 102 patients (age 62±14 years; 23% women) had a mean LVEF of 28±11% and RVEF of 44±12%. The left ventricular and right ventricular end diastolic volume index was 140±42 mL/m² and 81±27 mL/m², respectively. Eighty-six (84%) patients had a LVEF <35%, and 63 (62%) patients had right ventricular systolic dysfunction. Although there was a significant and moderate correlation between LVEF and RVEF (r=0.40, p<0.001), 32 of 86 patients (37%) with LVEF <35% had preserved RVEF, while 9 of 16 patients (56%) with LVEF ≥35% had right ventricular systolic dysfunction (Kappa=0.041).

Conclusions

Among patients being considered for an ICD, there is a positive but moderate correlation between LVEF and RVEF. A considerable proportion of patients who qualify for an ICD based on low LVEF have preserved RVEF, and vice versa.

Programmed Ventricular Stimulation to Risk Stratify for Early Cardioverter-Defibrillator Implantation to Prevent Tachyarrhythmias following Acute Myocardial Infarction (PROTECT-ICD): Trial Protocol, Background and Significance

The 'Programmed Ventricular Stimulation to Risk Stratify for Early Cardioverter-Defibrillator Implantation to Prevent Tachyarrhythmias following Acute Myocardial Infarction' (PROTECT-ICD) trial is an Australian-led multicentre randomised controlled trial targeting prevention of sudden cardiac death in patients who have at least moderately reduced cardiac function following a myocardial infarct (MI). The primary objective of the trial is to assess whether electrophysiological study to guide prophylactic implantation of an implantable cardioverter-defibrillator (ICD) early following MI (first 40 days) will lead to a significant reduction in sudden cardiac death and non-fatal arrhythmia. The secondary objective is to assess the utility of cardiac MRI (CMR) in assessing early myocardial characteristics, and its predictive value for both inducible ventricular tachycardia (VT) at EPS and SCD/ non-fatal arrhythmia at follow-up.

Treatment of Infected Cardiac Implantable Electronic Devices

With their rising benefits, cardiac implantable electronic devices (CIEDs) such as pacemakers and left ventricular assist devices (LVADs) have witnessed a sharp rise in use over the past 50 years. As indications for use broaden, so too does their widespread employment with its attendant rise of CIED infections. Such large numbers of infections have inspired various algorithms mandating treatment. Early diagnosis of inciting organisms is crucial to tailoring appropriate antibiotic and or antifungal treatment. In addition, surgical debridement and explant of the device have been a longstanding modality of care. More novel therapies focus on salvage of the device by way of serial washouts and instilling drug-eluting antibiotic impregnated beads into the wound. The wound is then serially debrided until clean and closed. This technique is better suited to patients whose device cannot be removed, patients who are poor candidates for cardiac surgery, or patients who have failed conventional prior treatments.

Novel Imaging Approaches for Predicting Arrhythmic Risk

Determination of ventricular arrhythmic risk is crucial for guiding management of cardiac disease. Although for patients at increased risk an implantable cardioverter-defibrillator is recommended, it is widely acknowledged that current criteria for device use based predominantly on left ventricular ejection fraction are deficient. Genesis of ventricular arrhythmias involves a complex interaction of myocardial substrate abnormalities, precipitating triggers, and modulating factors. There are much data showing that by more directly assessing these factors, noninvasive imaging using echocardiography, radionuclide imaging, and cardiac magnetic resonance enhances arrhythmic risk stratification beyond ejection fraction and commonly used electrocardiographic and serum biomarkers. It is anticipated that further technological advancements studied in well-designed clinical trials will provide both more precise determination of risk and guide therapies to enhanced survival and patient well-being.

Beyond ejection fraction: an integrative approach for assessment of cardiac structure and function in heart failure

Left ventricular ejection fraction (LVEF) has been the central parameter used for diagnosis and management in patients with heart failure. A good predictor of adverse outcomes in heart failure when below ∼45%, LVEF is less useful as a marker of risk as it approaches normal. As a measure of cardiac function, ejection fraction has several important limitations. Calculated as the stroke volume divided by end-diastolic volume, the estimation of ejection fraction is generally based on geometric assumptions that allow for assessment of volumes based on linear or two-dimensional measurements. Left ventricular ejection fraction is both preload- and afterload-dependent, can change substantially based on loading conditions, is only moderately reproducible, and represents only a single measure of risk in patients with heart failure. Moreover, the relationship between ejection fraction and risk in patients with heart failure is modified by factors such as hypertension, diabetes, and renal function. A more complete evaluation and understanding of left ventricular function in patients with heart failure requires a more comprehensive assessment: we conceptualize an integrative approach that incorporates measures of left and right ventricular function, left ventricular geometry, left atrial size, and valvular function, as well as non-imaging factors (such as clinical parameters and biomarkers), providing a comprehensive and accurate prediction of risk in heart failure.

Clinical Applications of Myocardial Innervation Imaging

Cardiac autonomic innervation plays an important role in regulating function. Adrenergic innervation imaging is possible with the norepinephrine analogue radiotracer iodine 123 meta-iodobenzylguanidine ((123)I-mIBG) and positron emitting tracers such carbon-11 hydroxyephedrine. (123)I-mIBG uptake is assessed globally via the heart to mediastinum ratio on planar images and regionally with tomographic imaging and has utility in various cardiac diseases. There is promise for guiding expensive invasive therapies such as implantable defibrillators, ventricular assist devices, and transplant. There are reports of utility in primary arrhythmic conditions, ischemic heart disease, and diabetes and after cardiac damaging chemotherapy.

Alternative research funding to improve clinical outcomes: model of prediction and prevention of sudden cardiac death

Although identification and management of cardiovascular risk markers have provided important population risk insights and public health benefits, individual risk prediction remains challenging. Using sudden cardiac death risk as a base case, the complex epidemiology of sudden cardiac death risk and the substantial new funding required to study individual risk are explored. Complex epidemiology derives from the multiple subgroups having different denominators and risk profiles, while funding limitations emerge from saturation of conventional sources of research funding without foreseeable opportunities for increases. A resolution to this problem would have to emerge from new sources of funding targeted to individual risk prediction. In this analysis, we explore the possibility of a research funding strategy that would offer business incentives to the insurance industries, while providing support for unresolved research goals. The model is developed for the case of sudden cardiac death risk, but the concept is applicable to other areas of the medical enterprise.

The clinical challenge of preventing sudden cardiac death immediately after acute ST-elevation myocardial infarction

Unfortunately, of all patients experiencing acute myocardial infarction (MI), usually in the form of ST-elevation MI, 25-35% will die of sudden cardiac death (SCD) before receiving medical attention, most often from ventricular fibrillation. For patients who reach the hospital, prognosis is considerably better and has improved over the years. Reperfusion therapy, best attained with primary percutaneous coronary intervention compared to thrombolysis, has made a big difference in reducing the risk of SCD early and late after ST-elevation MI. In-hospital SCD due to ventricular tachyarrhythmias is manageable, with either preventive measures or drugs or electrical cardioversion. There is general agreement for secondary prevention of SCD post-MI with implantation of a cardioverter defibrillator (ICD) when malignant ventricular arrhythmias occur late (>48 h) after an MI, and are not due to reversible or correctable causes. The major challenge remains that of primary prevention, that is, how to prevent SCD during the first 1-3 months after ST-elevation MI for patients who have low left ventricular ejection fraction and are not candidates for an ICD according to current guidelines, due to the results of two studies, which did not show any benefits of early (<40 days after an MI) ICD implantation. Two recent documents may provide direction as to how to bridge the gap for this early post-MI period. Both recommend an electrophysiology study to guide implantation of an ICD, at least for those developing syncope or non-sustained ventricular tachycardia, who have an inducible sustained ventricular tachycardia at the electrophysiology study. An ICD is also recommended for patients with indication for a permanent pacemaker due to bradyarrhythmias, who also meet primary prevention criteria for SCD.

Left ventricular diameter and risk stratification for sudden cardiac death

Background

Left ventricular (LV) diameter is routinely measured on the echocardiogram but has not been jointly evaluated with the ejection fraction (EF) for risk stratification of sudden cardiac death (SCD).

Methods and Results

From a large ongoing community‐based study of SCD (The Oregon Sudden Unexpected Death Study; population ≈1 million), SCD cases were compared with geographic controls. LVEF and LV diameter, measured using the LV internal dimension in diastole (categorized as normal, mild, moderate, or severe dilatation using American Society of Echocardiography definitions) were assessed from echocardiograms prior but unrelated to the SCD event. Cases (n=418; 69.5±13.8 years), compared with controls (n=329; 67.7±11.9 years), more commonly had severe LV dysfunction (EF ≤35%; 30.5% versus 18.8%; P<0.01) and larger LV diameter (52.2±10.5 mm versus 49.7±7.9 mm; P<0.01). Moderate or severe LV dilatation (16.3% versus 8.2%; P=0.001) and severe LV dilatation (8.1% versus 2.1%; P<0.001) were significantly more frequent in cases. In multivariable analysis, severe LV dilatation was an independent predictor of SCD (odds ratio 2.5 [95% CI 1.03 to 5.9]; P=0.04). In addition, subjects with both EF ≤35% and severe LV dilatation had higher odds for SCD compared with those with low EF only (odds ratio 3.8 [95% CI 1.5 to 10.2] for both versus 1.7 [95% CI 1.2 to 2.5] for low EF only), suggesting that severe LV dilatation additively increased SCD risk.

Conclusion

LV diameter may contribute to risk stratification for SCD independent of the LVEF. This readily available echocardiographic measure warrants further prospective evaluation.

A novel method to capture the onset of dynamic electrocardiographic ischemic changes and its implications to arrhythmia susceptibility

Background

This study investigates the hypothesis that morphologic analysis of intracardiac electrograms provides a sensitive approach to detect acute myocardial infarction or myocardial infarction‐induced arrhythmia susceptibility. Large proportions of irreversible myocardial injury and fatal ventricular tachyarrhythmias occur in the first hour after coronary occlusion; therefore, early detection of acute myocardial infarction may improve clinical outcomes.

Methods and Results

We developed a method that uses the wavelet transform to delineate electrocardiographic signals, and we have devised an index to quantify the ischemia‐induced changes in these signals. We recorded body‐surface and intracardiac electrograms at baseline and following myocardial infarction in 24 swine. Statistically significant ischemia‐induced changes after the initiation of occlusion compared with baseline were detectable within 30 seconds in intracardiac left ventricle (P<0.0016) and right ventricle–coronary sinus (P<0.0011) leads, 60 seconds in coronary sinus leads (P<0.0002), 90 seconds in right ventricle leads (P<0.0020), and 360 seconds in body‐surface electrocardiographic signals (P<0.0022). Intracardiac leads exhibited a higher probability of detecting ischemia‐induced changes than body‐surface leads (P<0.0381), and the right ventricle–coronary sinus configuration provided the highest sensitivity (96%). The 24‐hour ECG recordings showed that the ischemic index is statistically significantly increased compared with baseline in lead I, aVR, and all precordial leads (P<0.0388). Finally, we showed that the ischemic index in intracardiac electrograms is significantly increased preceding ventricular tachyarrhythmic events (P<0.0360).

Conclusions

We present a novel method that is capable of detecting ischemia‐induced changes in intracardiac electrograms as early as 30 seconds following myocardial infarction or as early as 12 minutes preceding tachyarrhythmic events.

Clinical profile, management, and outcome in patients with out of hospital cardiac arrest: insights from a 20-year registry

Background

There is limited information regarding the clinical characteristics and outcome of out of hospital cardiac arrest (OHCA) in Middle Eastern patients. The aim of this study was to evaluate clinical characteristics, treatment, and outcomes in patients admitted following OHCA at a single center in the Middle East over a 20-year period.

Methods

The data used for this hospital-based study were collected for patients hospitalized with OHCA in Doha, Qatar, between 1991 and 2010. Baseline clinical characteristics, in-hospital treatment, and outcomes were studied in comparison with the rest of the admissions.

Results

A total of 41,453 consecutive patients were admitted during the study period, of whom 987 (2.4%) had a diagnosis of OHCA. Their average age was 57±15 years, and 72.7% were males, 56.5% were Arabs, and 30.9% were South Asians. When compared with the rest of the admissions taken as a reference, patients with OHCA were more likely to have diabetes mellitus (42.8% versus 39.1%, respectively, P=0.02), prior myocardial infarction (21.8% versus 19.2%, P=0.04), and chronic renal failure (7.4% versus 3.9%, P=0.001), but were less likely to have dyslipidemia (16.9% versus 25.4%, P=0.001). Further, 52.6% of patients had preceding symptoms, the most common of which was chest pain (27.2%) followed by dyspnea (24.8%). An initially shockable rhythm (ventricular fibrillation or ventricular tachycardia) was present in 25.1% of OHCA patients, with ST segment elevation myocardial infarction documented in 30.0%. Severely reduced left ventricular systolic function (ejection fraction ≤35%) was present in 53.2% of OHCA patients; 42.9% had cardiogenic shock requiring use of inotropes at presentation. An intra-aortic balloon pump was inserted in 3.6% of cases. Antiarrhythmic medications were used in 27.4% and thrombolytic therapy in 13.9%, and 10.8% underwent a percutaneous coronary procedure (coronary angiography ± percutaneous coronary intervention). The in-hospital mortality rate was 59.8%.

Conclusion

OHCA was associated with higher incidences of diabetes, prior myocardial infarction, and chronic kidney disease as compared with the remaining admissions. Approximately half of the patients had no preceding symptoms. In-hospital mortality was high (59.8%), but similar to the internationally published data.

Long-term arrhythmia-free survival in patients with severe left ventricular dysfunction and no inducible ventricular tachycardia after myocardial infarction

BACKGROUND

A negative electrophysiology study (EPS) may delineate a subgroup of patients with severely impaired left ventricular ejection fraction (LVEF) whose care can be safely managed long-term without an implantable cardioverter-defibrillator.

METHODS AND RESULTS

Consecutive patients treated with primary percutaneous coronary intervention for ST-segment-elevation myocardial infarction underwent early (median 4 days) LVEF assessment. Patients with LVEF ≤40% underwent EPS. A prophylactic implantable cardioverter-defibrillator was implanted for a positive (inducible monomorphic ventricular tachycardia) but not a negative (no inducible ventricular tachycardia or inducible ventricular fibrillation/flutter) EPS result. Patients who would have become eligible for a late primary prevention implantable cardioverter-defibrillator with LVEF ≤30% or ≤35% with New York Heart Association class II/III heart failure were included and analyzed according to EPS result. Patients with LVEF >40%, ineligible for EPS, were followed up as control subjects (n=1286). The primary end point was survival free of death or arrhythmia (resuscitated cardiac arrest or sustained ventricular tachycardia/ventricular fibrillation). EPS performed in 128 patients with LVEF ≤30% or with LVEF ≤35% and heart failure was negative in 63% (n=80) and positive in 37% (n=48). Implantable-cardioverter defibrillators were implanted in <0.1%, 4%, and 90% of control, EPS-negative, and EPS-positive patients, respectively. The distribution of time to death or arrhythmia was comparable in control patients and EPS-negative patients with LVEF ≤30% or with LVEF ≤35% and heart failure (P=0.738), who both differed significantly from EPS-positive patients (P<0.001). At 3 years, 91.8 ± 3.2%, 93.4 ± 1.0%, and 62.7 ± 7.5% of control, EPS-negative, and EPS-positive patients were free of death or arrhythmia, respectively.

CONCLUSIONS

Revascularized patients with ST-segment-elevation myocardial infarction with severely impaired left ventricular function but no inducible ventricular tachycardia have a favorable long-term prognosis without the protection of an implantable cardioverter-defibrillator.

Frequency and determinants of implantable cardioverter defibrillator deployment among primary prevention candidates with subsequent sudden cardiac arrest in the community

BACKGROUND

The prevalence rates and influencing factors for deployment of primary prevention implantable cardioverter defibrillators (ICDs) among subjects who eventually experience sudden cardiac arrest in the general population have not been evaluated.

METHODS AND RESULTS

Cases of adult sudden cardiac arrest with echocardiographic evaluation before the event were identified from the ongoing Oregon Sudden Unexpected Death Study (population approximately 1 million). Eligibility for primary ICD implantation was determined from medical records based on established guidelines. The frequency of prior primary ICD implantation in eligible subjects was evaluated, and ICD nonrecipients were characterized. Of 2093 cases (2003-2012), 448 had appropriate pre- sudden cardiac arrest left ventricular ejection fraction information available. Of these, 92 (20.5%) were eligible for primary ICD implantation, 304 (67.9%) were ineligible because of left ventricular ejection fraction >35%, and the remainder (52, 11.6%) had left ventricular ejection fraction ≤35% but were ineligible on the basis of clinical guideline criteria. Among eligible subjects, only 12 (13.0%; 95% confidence interval, 6.1%-19.9%) received a primary ICD. Compared with recipients, primary ICD nonrecipients were older (age at ejection fraction assessment, 67.1±13.6 versus 58.5±14.8 years, P=0.05), with 20% aged ≥80 years (versus 0% among recipients, P=0.11). Additionally, a subgroup (26%) had either a clinical history of dementia or were undergoing chronic dialysis.

CONCLUSIONS

Only one fifth of the sudden cardiac arrest cases in the community were eligible for a primary prevention ICD before the event, but among these, a small proportion (13%) were actually implanted. Although older age and comorbidity may explain nondeployment in a subgroup of these cases, other determinants such as socioeconomic factors, health insurance, patient preference, and clinical practice patterns warrant further detailed investigation.

Multi-contrast late enhancement CMR determined gray zone and papillary muscle involvement predict appropriate ICD therapy in patients with ischemic heart disease

BACKGROUND

Myocardial infarct heterogeneity indices including peri-infarct gray zone are predictors for spontaneous ventricular arrhythmias events after ICD implantation in patients with ischemic heart disease. In this study we hypothesize that the extent of peri-infarct gray zone and papillary muscle infarct scores determined by a new multi-contrast late enhancement (MCLE) method may predict appropriate ICD therapy in patients with ischemic heart disease.

METHODS

The cardiovascular magnetic resonance (CMR) protocol included LV functional parameter assessment and late gadolinium enhancement (LGE) CMR using the conventional method and MCLE post-contrast. The proportion of peri-infarct gray zone, core infarct, total infarct relative to LV myocardium mass, papillary muscle infarct scores, and LV functional parameters were statistically compared between groups with and without appropriate ICD therapy during follow-up.

RESULTS

Twenty-five patients with prior myocardial infarct for planned ICD implantation (age 64±10 yrs, 88% men, average LVEF 26.2±10.4%) were enrolled. All patients completed the CMR protocol and 6-46 months follow-up at the ICD clinic. Twelve patients had at least one appropriate ICD therapy for ventricular arrhythmias at follow-up. Only the proportion of gray zone measured with MCLE and papillary muscle infarct scores demonstrated a statistically significant difference (P < 0.05) between patients with and without appropriate ICD therapy for ventricular arrhythmias; other CMR derived parameters such as LVEF, core infarct and total infarct did not show a statistically significant difference between these two groups.

CONCLUSIONS

Peri-infarct gray zone measurement using MCLE, compared to using conventional LGE-CMR, might be more sensitive in predicting appropriate ICD therapy for ventricular arrhythmia events. Papillary muscle infarct scores might have a specific role for predicting appropriate ICD therapy although the exact mechanism needs further investigation.