The relationships among ventricular arrhythmias, left ventricular dysfunction, and mortality in the 2 years after myocardial infarction

Overexpression of Sema3a in myocardial infarction border zone decreases vulnerability of ventricular tachycardia post-myocardial infarction in rats

The expression of the chemorepellent Sema3a is inversely related to sympathetic innervation. We investigated whether overexpression of Sema3a in the myocardial infarction (MI) border zone could attenuate sympathetic hyper-innervation and decrease the vulnerability to malignant ventricular tachyarrhythmia (VT) in rats. Survived MI rats were randomized to phosphate buffered saline (PBS, n = 12); mock lentivirus (MLV, n = 13) and lentivirus-mediated overexpression of Sema3a (SLV, n = 13) groups. Sham-operated rats served as control group (CON, n = 20). Cardiac function and electrophysiological study (PES) were performed at 1 week later. Blood and tissue samples were collected for histological analysis, epinephrine (EPI), growth-associated factor 43 (GAP43) and tyrosine hydroxylase (TH) measurements. QTc intervals were significantly shorter in SLV group than in PBS and MLV groups (168.6 ± 7.8 vs. 178.1 ± 9.5 and 180.9 ± 8.2 ms, all P < 0.01). Inducibility of VT by PES was significantly lower in the SLV group [30.8% (4/13)] than in PBS [66.7% (8/12)] and MLV [61.5% (8/13)] groups (P < 0.05). mRNA and protein expressions of Sema3a were significantly higher and the protein expression of GAP43 and TH was significantly lower at 7 days after transduction in SLV group compared with PBS, MLV and CON groups. Myocardial EPI in the border zone was also significantly lower in SLV group than in PBS and MLV group (8.73 ± 1.30 vs. 11.94 ± 1.71 and 12.24 ± 1.54 μg/g protein, P < 0.001). Overexpression of Sema3a in MI border zone could reduce the inducibility of ventricular arrhythmias by reducing sympathetic hyper-reinnervation after infarction.

Sudden Cardiac Death: A Review Focused on Cardiovascular Imaging

Sudden cardiac death (SCD) is defined as natural death due to cardiac causes, heralded by abrupt loss of consciousness within 1 h of the onset of acute symptoms; pre-existing heart disease may have been known to be present but the time and mode of death are unexpected. Prediction and prevention of SCD is an area of active investigation, but considerable challenges persist that limit the efficacy and cost-effectiveness of available methodologies. It was well-recognized that optimization of SCD risk stratification would require integration of multi-disciplinary efforts at the bench and bedside, with studies in the general population. This integration has yet to be effectively accomplished. There is also increasing awareness that more investigation needs to be directed toward the identification of early predictors of SCD. Significant advancements have recently occurred for risk prediction in the inherited channelopathies and other inherited conditions that predispose to SCD, but there is much to be accomplished in this regard for the more common complex phenotypes, such as SCD among patients with coronary artery disease. A multimodality imaging approach is actually the most important tool to provide comprehensive information on different pathophysiological mechanisms related to SCD.

The Relationship between Left Atrial Volume and Ventricular Arrhythmias in the Patients with Dilated Cardiomyopathy

BACKGROUND

The present study aimed to investigate the relationship between Left Atrial Volume (LAV), a marker of diastolic dysfunction, and the frequency of malignant ventricular arrhythmia in the patients with left ventricular dysfunction and a previously implanted Implantable Cardioverter Defibrillator (ICD) device.

METHODS

This cross-sectional study was conducted on 32 patients with ischemic or idiopathic dilated cardiomyopathy, each having had an ICD device implanted at least 1 year beforehand. The ventricular arrhythmia episodes which were detected and stored by the device were retrieved and evaluated. In addition to routine echocardiographic measurements, all the patients had their LAV and LAV indexes calculated. After all, student's t-test, Mann-Whitney U test, and Pearson correlation were used to analyze the data. Besides, P value < 0.05 was considered as statistically significant.

RESULTS

This study was conducted on 4 female and 28 male patients with the mean age of 58.41 ± 9.97 years. Among the study patients, 21 had at least one previous myocardial infarction. In addition, 17 patients had experienced sustained VT or VF within the last year. No significant difference was found between the patients with and without malignant ventricular arrhythmias (sustained VT or VF) regarding LAV (17 patients with arrhythmia (68 + 23.39 mL) vs. 15 patients without arrhythmia (55.13 ± 20.41 mL); P = 0.100). However, the LAV index was significantly higher in the patients with arrhythmia compared to those without arrhythmia (39.27 ± 12.19 mL / m2 vs. 25.18 ± 7.45 mL / m2; P = 0.004). Both LAV (73.33 ± 17.64 mL and 57.52 ± 23.15 mL, respectively; P = 0.040) and LAV index (40.86 ± 8.47 mL / m2 and 28.20 ± 11.77 mL / m2, respectively; P = 0.010) were significantly greater in the patients with ICD shock therapy within the last year compared to the others. However, both groups were similar regarding Left Ventricular Volume (LVV), LVV index, and ejection fraction.

CONCLUSIONS

The study findings demonstrated that LAV and LAV index could be used in detecting the patients who are at high risk of malignant ventricular arrhythmias.

Induced pluripotent stem cell-derived cardiomyocytes for cardiovascular disease modeling and drug screening

Human induced pluripotent stem cells (hiPSCs) have emerged as a novel tool for drug discovery and therapy in cardiovascular medicine. hiPSCs are functionally similar to human embryonic stem cells (hESCs) and can be derived autologously without the ethical challenges associated with hESCs. Given the limited regenerative capacity of the human heart following myocardial injury, cardiomyocytes derived from hiPSCs (hiPSC-CMs) have garnered significant attention from basic and translational scientists as a promising cell source for replacement therapy. However, ongoing issues such as cell immaturity, scale of production, inter-line variability, and cell purity will need to be resolved before human clinical trials can begin. Meanwhile, the use of hiPSCs to explore cellular mechanisms of cardiovascular diseases in vitro has proven to be extremely valuable. For example, hiPSC-CMs have been shown to recapitulate disease phenotypes from patients with monogenic cardiovascular disorders. Furthermore, patient-derived hiPSC-CMs are now providing new insights regarding drug efficacy and toxicity. This review will highlight recent advances in utilizing hiPSC-CMs for cardiac disease modeling in vitro and as a platform for drug validation. The advantages and disadvantages of using hiPSC-CMs for drug screening purposes will be explored as well.

Outcome of prolonged ventricular fibrillation and CPR in a rat model of chronic ischemic left ventricular dysfunction

Patients with chronic left ventricular (LV) dysfunction are assumed to have a lower chance of successful CPR and lower likelihood of ultimate survival. However, these assumptions have rarely been documented. Therefore, we investigated the outcome of prolonged ventricular fibrillation (VF) and CPR in a rat model of chronic LV dysfunction. Sprague-Dawley rats were randomized to (1) chronic LV dysfunction: animals underwent left coronary artery ligation; and (2) sham control. Echocardiography was used to measure cardiac performance before surgery and 4 weeks after surgery. Four weeks after surgical intervention, 8 min of VF was induced and defibrillation was delivered after 8 min of CPR. LV dilation and low ejection fraction were observed 4 weeks after coronary ligation. With optimal chest compressions, coronary perfusion pressure values during CPR were well maintained and indistinguishable between groups. There were no differences in resuscitability and numbers of shock required for successful resuscitation between groups. Despite the significantly decreased cardiac index in LV dysfunction animals before induction of VF, no differences in cardiac index were observed between groups following resuscitation, which was associated with the insignificant difference in postresuscitation survival. In conclusion, the outcomes of CPR were not compromised by the preexisting chronic LV dysfunction.

Ketanserin improves cardiac performance after myocardial infarction in spontaneously hypertensive rats partially through restoration of baroreflex function

AIM

Baroreflex dysfunction is associated with a higher rate of sudden death after myocardial infarction (MI). Ketanserin enhances baroreflex function in rats. The present work was designed to examine whether ketanserin improves the post-MI cardiac function and to explore the possible mechanism involved.

METHODS

Spontaneously hypertensive rats (SHR) were treated with ketanserin (0.3 mg·kg(-1)·d(-1)). Two weeks later, blood pressure and baroreflex function were measured, followed by a ligation of the left coronary artery. The expressions of vesicular acetylcholine transporter (VAChT) and α7 nicotinic acetylcholine receptor (α7-nAChR) in ischemic myocardium, angiogenesis, cardiac function, and left ventricular (LV) remodeling were evaluated subsequently.

RESULTS

Ketanserin significantly improved baroreflex sensitivity (0.62±0.21 vs 0.34±0.12 ms/mmHg, P<0.01) and vagal tonic activity (heart rate changes in response to atropine, 54.8±16.2 vs 37.6±13.4 bpm, P<0.01) without affecting the blood pressure or basic heart rate in SHR. Treatment of SHR with ketanserin prominently improved cardiac function and alleviated LV remodeling, as reflected by increases in the ejection fraction, fractional shortening, and LV systolic pressure as well as decreases in LV internal diameter and LV relative weight. The capillary density, vascular endothelial growth factor expression, and blood flow in the ischemic myocardium were significantly higher in the ketanserin-treated group. In addition, ketanserin markedly increased the expression of VAChT and α7-nAChR in ischemic myocardium.

CONCLUSION

Ketanserin improved post-MI cardiac function and angiogenesis in ischemic myocardium. The findings provide a mechanistic basis for restoring baroreflex function using ketanserin in the treatment of MI.

Cardiac aetiology of cardiac arrest: percutaneous coronary interventions during and after cardiopulmonary resuscitation

Management and prevention of cardiac arrest in the setting of heart disease is a challenge for modern cardiology. After reviewing the aetiology of sudden cardiac death and discussing the way to identify candidates at risk, we emphasise the role of percutaneous coronary interventions during and after cardiopulmonary resuscitation in the treatment of patients with return of spontaneous circulation after cardiac arrest.

Prevalence of ventricular arrhythmia and its associated factors in nondialyzed chronic kidney disease patients

BACKGROUND AND OBJECTIVES

Sudden cardiac death is the most common cause of mortality in chronic kidney disease patients, and it occurs mostly due to ventricular arrhythmias. In this study, we aimed at investigating the prevalence of ventricular arrhythmia and the factors associated with its occurrence in nondialyzed chronic kidney disease patients.

DESIGN SETTING PARTICIPANTS AND MEASUREMENTS

This cross-sectional study evaluated 111 chronic kidney disease patients (estimated glomerular filtration rate 34.7±16.1 mL/min/1.73 m(2), 57±11.4 years, 60% male, 24% diabetics). Ventricular arrhythmia was assessed by 24-hour electrocardiogram. Left ventricular hypertrophy (echocardiogram), 24-hour ambulatory blood pressure monitoring, and coronary artery calcification (multi-slice computed tomography) and laboratory parameters were also evaluated.

RESULTS

Ventricular arrhythmia was found in 35% of the patients. Non-controlled hypertension was observed in 21%, absence of systolic decency in 29%, left ventricular hypertrophy in 27%, systolic dysfunction in 10%, and coronary artery calcification in 49%. Patients with ventricular arrhythmia were older (p<0.001), predominantly men (p = 0.009), had higher estimated glomerular filtration rate (p = 0.03) and hemoglobin (p = 0.005), and lower intact parathyroid hormone (p = 0.024) and triglycerides (p = 0.011) when compared to patients without ventricular arrhythmia. In addition, a higher left ventricular mass index (p = 0.002) and coronary calcium score (p = 0.002), and a lower ejection fraction (p = 0.001) were observed among patients with ventricular arrhythmia. In the multiple logistic regression analysis, aging, increased hemoglobin levels and reduced ejection fraction were independently related to the presence of ventricular arrhythmia.

CONCLUSIONS

Ventricular arrhythmia is prevalent in nondialyzed chronic kidney disease patients. Age, hemoglobin levels and ejection fraction were the factors associated with ventricular arrhythmia in these patients.

The reverse mode switch algorithm: how well does it work?

BACKGROUND

The performance of the Reverse Mode Switch (RMS) algorithm, aimed at minimizing right ventricular pacing by operating in the AAI(R) mode with switch to the DDD(R) mode if atrioventricular (AV) conduction loss is detected, is not well known.

OBJECTIVE

To determine the appropriateness of the RMS episodes available from patient follow-up data at our center.

METHODS

Patients with the TELIGEN dual-chamber implantable cardioverter-defibrillator and the RMS algorithm activated were identified. The RMS episodes with available electrograms were analyzed and classified as appropriate (AV conduction loss) or inappropriate (non-AV conduction loss) events. Cumulative percentage of ventricular pacing and amount of premature ventricular complexes (PVCs) were recorded.

RESULTS

Of 21 patients, RMS episodes had occurred in 19 of them, with a mean of 527 episodes per month. Of the 172 RMS episodes available for analysis, 27 (16%) were classified as appropriate and 145 (84%) as inappropriate. Almost all (91%) inappropriate RMS episodes were due to PVC, and there was a positive correlation between the number of total RMS episodes per month and the number of PVCs per month (P < .0005). Considering patients with only inappropriate RMS episodes (n = 11), there was a positive correlation between the percentage of ventricular pacing and the number of RMS episodes per month (P < .05).

CONCLUSIONS

A large majority of the RMS episodes available for analysis inappropriately triggered switch from the AAI(R) mode to the DDD(R) mode owing to PVCs. Patients with the RMS algorithm and elevated PVC burden are probably at risk of a high percentage of unnecessary right ventricular pacing.

Microvolt T wave alternans in adults with congenital heart diseases characterized by right ventricle pathology or single ventricle physiology: a case control study

Background

Among adults with congenital heart diseases (CHD) evaluation of sudden cardiac death (SCD) risk remains a great challenge. Although microvolt T-wave alternans has been incorporated into SCD risk stratification algorithm, its role in adults with CHD still requires investigation. We sought to determine the incidence of MTWA in this specific group and its coincidence with ventricular arrhythmia (VA) and other clinical findings presumably associated with SCD.

Methods

A case–control study was performed in which 102 patients with CHD characterized by right ventricle pathology or single ventricle physiology (TGA, UVH, Ebstein’s anomaly, ccTGA, Eisenmenger syndrome, DORV, CAT, unoperated ToF) were compared to 45 age- and sex-matched controls. All subjects underwent spectral MTWA test, ambulatory ecg monitoring, cardiopulmonary test, BNP assessment. After excluding technically inadequate traces, the remaining MTWA results were classified as positive(+), negative(−) and indeterminate(ind). Due to similar prognostic significance MTWA(+) and (ind) were combined into a common group labeled ‘abnormal’.

Results

Abnormal MTWA was present more often in the study group, compared to controls (39.2% vs 2.3%, p = 0.00001). Sustained ventricular tachycardia (sVT) was observed more often among subjects with abnormal MTWA compared to MTWA(−): 19.4% vs 3.6%, p = 0.026. The patients with abnormal MTWA had a lower blood saturation (p = 0.047), more often were males (p = 0.031), had higher NYHA class (p = 0.04), worse cardiopulmonary parameters: %PeakVO₂ (p = 0.034), %HRmax (p = 0.003). Factors proven to increase probability of abnormal MTWA on multivariate linear regression analysis were: sVT (OR = 20.7, p = 0.037) and male gender (OR = 15.9, p = 0.001); on univariate analysis: male gender (OR = 2.7, p = 0.021), presence of VA (OR = 2.6, p = 0.049), NYHA > I (OR = 2.06, p = 0.033), %HRmax (OR = 0.94, p = 0.005), %PeakVO₂ (OR = 0.97, p = 0.042), VE/VCO₂slope (OR = 1.05, p = 0.037).

Conclusions

Abnormal MTWA occurs significantly more often in adults with the chosen forms of CHD than among healthy subjects. The probability of abnormal MTWA increases in patients with malignant VA, in males and among subjects with heart failure and cyanosis. MTWA might be of potential role in risk stratification for SCD in adults with CHD.

Nonischemic mitral regurgitation: prognostic value of nonsustained ventricular tachycardia after mitral valve surgery

BACKGROUND

Nonsustained ventricular tachycardia (VT), frequent in unoperated severe mitral regurgitation (MR), confers mortality risk [sudden death (SD) and cardiac death (CD)]. The prognostic value of VT after mitral valve surgery (MVS) is unknown; we aimed to define this prognostic value and to assess its modulation by left (LV) and/or right (RV) ventricular ejection fraction (EF) for mortality after MVS.

METHODS

In 57 patients (53% females, aged 58 ± 12 years) with severe MR prospectively followed before and after MVS, we performed 24-hour ambulatory electrocardiograms approximately annually. LVEF and RVEF were determined within 1 year after MVS by radionuclide cineangiography.

RESULTS

During 9.52 ± 3.49 endpoint-free follow-up years, late postoperative CD occurred in 11 patients (7 SD, 4 heart failures). In univariable analysis, >1 VT episode after MVS predicted SD (p < 0.01) and CD (SD or heart failure; p < 0.04). Subnormal postoperative RVEF predicted CD (p < 0.04). When adjusted for preoperative age, gender, etiology or antiarrhythmics, both postoperative VT and RVEF predicted CD (p ≤ 0.05). When postoperative VT and RVEF were both in the multivariable model, only subnormal RVEF predicted CD (p < 0.04). Among those with normal RVEF, VT >1 episode predicted SD (p = 0.03).

CONCLUSION

Postoperative VT and subnormal RVEF predict late postoperative deaths in nonischemic MR. Their assessment may aid patient management.

Mechanisms of arrhythmias and conduction disorders in older adults

Aging is associated with an increased prevalence of cardiac arrhythmias, which contribute to higher morbidity and mortality in the elderly. The frequency of cardiac arrhythmias, particularly atrial fibrillation and ventricular tachyarrhythmia, is projected to increase as the population ages, greatly impacting health care resource utilization. Several clinical factors associated with the risk of arrhythmias have been identified in the population, yet the molecular bases for the increased predisposition to arrhythmogenesis in the elderly are not fully understood. This review highlights the epidemiology of cardiac dysrhythmias, changes in cardiac structure and function associated with aging, and the basis for arrhythmogenesis in the elderly.

A combined algorithm for T-wave alternans qualitative detection and quantitative measurement

BACKGROUND

T-wave alternans (TWA) provides a noninvasive and clinically useful marker for the risk of sudden cardiac death (SCD). Current most widely used TWA detection algorithms work in two different domains: time and frequency. The disadvantage of the spectral analytical techniques is that they treat the alternans signal as a stationary wave with a constant amplitude and a phase. They cannot detect non-stationary characteristics of the signal. The temporal domain methods are sensitive to the alignment of the T-waves. In this study, we sought to develop a robust combined algorithm (CA) to assess T-wave alternans, which can qualitatively detect and quantitatively measure TWA in time domain.

METHODS

The T wave sequences were extracted and the total energy of each T wave within the specified time-frequency region was calculated. The rank-sum test was applied to the ranked energy sequences of T waves to detect TWA qualitatively. The ECG containing TWA was quantitatively analyzed with correlation method.

RESULTS

Simulation test result proved a mean sensitivity of 91.2% in detecting TWA, and for the SNR not less than 30 dB, the accuracy rate of detection achieved 100%. The clinical data experiment showed that the results from this method vs. spectral method had the correlation coefficients of 0.96.

CONCLUSIONS

A novel TWA analysis algorithm utilizing the wavelet transform and correlation technique is presented in this paper. TWAs are not only correctly detected qualitatively in frequency domain by energy value of T waves, but the alternans frequency and amplitude in temporal domain are measured quantitatively.

Sudden death

Sudden death is probably the greatest challenge in modern cardiology. After reviewing its history, we describe the epidemiology of sudden death and its associated diseases. We highlight its physiopathologic aspects, including the factors that act on vulnerable myocardium triggering the final arrhythmia, mainly ventricular fibrillation and, to a lesser extent, bradycardia and sudden death. We emphasize the relevance of acute ischemia, ventricular dysfunction and genetic factors, not only in genetic heart disease, but also as triggers of sudden death in acute and chronic ischemic heart disease. Finally, we describe the best way to identify candidates at risk, discuss how to prevent sudden death, and outline the best approach to managing a patient resuscitated from cardiac arrest. Full English text available from:www.revespcardiol.org.

Sudden cardiac death in patients with human immunodeficiency virus infection

OBJECTIVES

The aim of this study was to determine the incidence and clinical characteristics of sudden cardiac death (SCD) in patients with human immunodeficiency virus (HIV) infection.

BACKGROUND

As the HIV-infected population ages, cardiovascular disease prevalence and mortality are increasing, but the incidence and features of SCD have not yet been described.

METHODS

The records of 2,860 consecutive patients in a public HIV clinic in San Francisco between April 2000 and August 2009 were examined. Identification of deaths, causes of death, and clinical characteristics were obtained by search of the National Death Index and/or clinic records. SCDs were determined using published retrospective criteria: 1) the International Classification of Diseases-10th Revision, code for all cardiac causes of death; and (2) circumstances of death meeting World Health Organization criteria.

RESULTS

Of 230 deaths over a median of 3.7 years of follow-up, 30 (13%) met SCD criteria, 131 (57%) were due to acquired immune deficiency syndrome (AIDS), 25 (11%) were due to other (natural) diseases, and 44 (19%) were due to overdoses, suicides, or unknown causes. SCDs accounted for 86% of all cardiac deaths (30 of 35). The mean SCD rate was 2.6 per 1,000 person-years (95% confidence interval: 1.8 to 3.8), 4.5-fold higher than expected. SCDs occurred in older patients than did AIDS deaths (mean 49.0 vs. 44.9 years, p = 0.02). Compared with AIDS and natural deaths combined, SCDs had a higher prevalence of prior myocardial infarction (17% vs. 1%, p < 0.0005), cardiomyopathy (23% vs. 3%, p < 0.0005), heart failure (30% vs. 9%, p = 0.004), and arrhythmias (20% vs. 3%, p = 0.003).

CONCLUSIONS

SCDs account for most cardiac and many non-AIDS natural deaths in HIV-infected patients. Further investigation is needed to ascertain underlying mechanisms, which may include inflammation, antiretroviral therapy interruption, and concomitant medications.

Incidence, prognosis, and factors associated with cardiac arrest in patients hospitalized with acute coronary syndromes (the Global Registry of Acute Coronary Events Registry)

OBJECTIVES

Contemporary data are lacking with respect to the incidence rates of, factors associated with, and impact of cardiac arrest from ventricular fibrillation or tachycardia (VF-CA) on hospital survival in patients admitted with an acute coronary syndrome (ACS). The objectives of this multinational study were to characterize trends in the magnitude of in-hospital VF-CA complicating an ACS and to describe its impact over time on hospital prognosis.

METHODS

In 59 161 patients enrolled in the Global Registry of Acute Coronary Events Study between 2000 and 2007, we determined the incidence, prognosis, and factors associated with VF-CA.

RESULTS

Overall, 3618 patients (6.2%) developed VF-CA during their hospitalization for an ACS. Incidence rates of VF-CA declined over time. Patients who experienced VF-CA were on average older and had a greater burden of cardiovascular disease, yet were less likely to receive evidence-based cardiac therapies than patients in whom VF-CA did not occur. Hospital death rates were 55.3% and 1.5% in patients with and without VF-CA, respectively. There was a greater than 50% decline in the hospital death rates associated with VF-CA during the years under study. Patients with a VF-CA occurring after 48 h were at especially high risk for dying during hospitalization (82.8%).

CONCLUSION

Despite reductions in the magnitude of, and short-term mortality from, VF-CA, VF-CA continues to exert an adverse effect on survival among patients hospitalized with an ACS. Opportunities exist to improve the identification and treatment of ACS patients at risk for VF-CA to reduce the incidence of, and mortality from, this serious arrhythmic disturbance.

Cardiovascular magnetic resonance characterization of peri-infarct zone remodeling following myocardial infarction

BACKGROUND

Clinical studies implementing late gadolinium-enhanced (LGE) cardiovascular magnetic resonance (CMR) studies suggest that the peri-infarct zone (PIZ) contains a mixture of viable and non-viable myocytes, and is associated with greater susceptibility to ventricular tachycardia induction and adverse cardiac outcomes. However, CMR data assessing the temporal formation and functional remodeling characteristics of this complex region are limited. We intended to characterize early temporal changes in scar morphology and regional function in the PIZ.

METHODS AND RESULTS

CMR studies were performed at six time points up to 90 days after induction of myocardial infarction (MI) in eight minipigs with reperfused, anterior-septal infarcts. Custom signal density threshold algorithms, based on the remote myocardium, were applied to define the infarct core and PIZ region for each time point. After the initial post-MI edema subsided, the PIZ decreased by 54% from day 10 to day 90 (p = 0.04). The size of infarct scar expanded by 14% and thinned by 56% from day 3 to 12 weeks (p = 0.004 and p < 0.001, respectively). LVEDV increased from 34.7. ± 2.2 ml to 47.8 ± 3.0 ml (day 3 and week 12, respectively; p < 0.001). At 30 days post-MI, regional circumferential strain was increased between the infarct scar and the PIZ (-2.1 ± 0.6 and -6.8 ± 0.9, respectively;* p < 0.05).

CONCLUSIONS

The PIZ is dynamic and decreases in mass following reperfused MI. Tensile forces in the PIZ undergo changes following MI. Remodeling characteristics of the PIZ may provide mechanistic insights into the development of life-threatening arrhythmias and sudden cardiac death post-MI.

Parasympathetic alteration during sub-clinical seizures

INTRODUCTION

Autonomic instability is considered a contributing factor in sudden unexpected death in epilepsy (SUDEP). The aim of this pilot study was to measure parasympathetic activity in sub-clinical seizures to investigate autonomic instability.

MATERIALS AND METHODS

A prospective study based on Video-electroencephalography (EEG)/electrocardiography (ECG)/oxygen saturation (SAO2) recordings was selected from patients having sub-clinical seizures during stage 3 or 4 sleep. We analysed R-R intervals in the ECG from 1-min prior to the electrographic onset to the end of sub-clinical seizures. Matched non-ictal R-R baseline measurements were selected from stages 3 or 4 sleep. R-R interval data were analysed using NeuroScope software providing a cardiac index of parasympathetic activity (CIPA). BioSignal short-term heart rate variability (HRV) software was used to analyse the same R-R interval data previously analysed using NeuroScope except that sub-clinical seizure data was embedded within 5-min epochs and compared to 5-min epochs of non-ictal measurements.

RESULTS

A total of 33 sub-clinical seizures were recorded from 11 patients comprising 19 generalised sub-clinical seizures (2 patients), 9 right temporal lobe sub-clinical seizures (5 patients) and 5 left temporal lobe sub-clinical seizures (4 patients) were compared to matched non-ictal measurements. Parasympathetic activity was clearly altered during total sub-clinical seizures in terms of the CIPA (p<0.001) and 5-min HRV high frequency (HF) % (p=0.026) measures. Generalised sub-clinical seizures resulted in increased cardiac parasympathetic activity whereas temporal lobe seizures were associated with a decrease in parasympathetic activity.

CONCLUSION

This pilot study indicates that parasympathetic changes occur during sub-clinical seizures. Generalised sub-clinical seizures may be associated with more autonomic instability compared to temporal lobe sub-clinical seizures.

Association of heart rate variability with arrhythmic events in patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is associated with an increased risk of sudden cardiac death (SCD). Risk stratification of ARVC/D patients, however, remains an unresolved issue. In this study we investigated whether heart rate variability (HRV) can be helpful in identifying ARVC/D patients with increased risk of arrhythmic events.

METHODS AND RESULTS

We studied 30 consecutive patients (17 males; 45.4 ± 18 years) with ARVC/D, diagnosed according to guideline criteria; 15 patients (50%) had received an implantable cardioverter defibrillator (ICD) for primary SCD prevention. HRV was assessed on 24-h ECG Holter monitoring. The primary endpoint was the occurrence of major arrhythmic events (SCD, sustained ventricular tachycardia (VT), ICD therapy for sustained VT or ventricular fibrillation (VF)). During the follow-up period (19 ± 7 months), no deaths occurred, but 5 patients (17%) experienced arrhythmic events (4 VTs and 1 VF, all in the ICD group). All HRV parameters were significantly lower in patients with, compared with those without, arrhythmic events. Low-frequency amplitude was the most significant HRV variable associated with arrhythmic events in univariate Cox regression analysis (P=0.017), and was the only significant predictor of arrhythmic events in multivariable regression analysis (hazard ratio 0.88, P=0.047), together with unexplained syncope (hazard ratio 16.1, P=0.039).

CONCLUSIONS

Our data show that among ARVC/D patients HRV analysis might be helpful in identifying those with increased risk of major arrhythmic events.

Review on Non-Invasive Risk Stratification of Sudden Cardiac Death

Sudden cardiac death (SCD) is one of the most significant and challenging problems facing modern medicine today given its unpredictable nature. The evaluation of the patient at risk for sudden cardiac death still remains a complex task. The use of ICDs (implantable cardioverter defibrillators) remains the mainstay of primary prevention of sudden cardiac death. However, much remains to be determined on how best to identify patients at high risk of sudden cardiac death who would most benefit from ICD implantations. This paper will review the current issues in the risk assessment of sudden cardiac death and non-invasive markers of sudden death.

Baroreflex deficiency hampers angiogenesis after myocardial infarction via acetylcholine-α7-nicotinic ACh receptor in rats

AIMS

Angiogenesis is critical for re-establishing blood supply to ischaemic myocardium after myocardial infarction (MI). Human studies have associated arterial baroreflex (ABR) deficiency with higher rate of sudden death after MI. The present work was designed to examine whether ABR deficiency affects angiogenesis in MI rats.

METHODS AND RESULTS

Baroreflex sensitivity (BRS) was determined in conscious rats at 1 month after occlusion of the left anterior descending coronary artery. The survival time was significantly shorter in Sprague-Dawley rats with BRS <0.60 ms/mmHg vs. those with BRS ≥0.60 ms/mmHg. Sinoaortic denervation destroyed ABR, and decreased capillary density, regional blood flow and vascular endothelial growth factor (VEGF) concentration after MI. Ketanserin (0.6 mg/kg/day) enhanced BRS, and increased capillary density, regional blood flow, and VEGF. Sinoaortic denervation also reduced the expression of vesicular acetylcholine (ACh) transporter and α7-nicotinic ACh receptor (α7-nAChR). Angiogenesis after MI was significantly attenuated in α7-nAChR knockout mice. In contrast, increase in endogenous ACh with cholinesterase inhibitor pyridostigmine (30 mg/kg/day) increased angiogenesis after MI. In cultured cardiac microvascular endothelial cells, ACh stimulated the expression of VEGF, phosphorylation of VEGF receptor 2, and tube formation in a manner dependent upon α7-nAChR.

CONCLUSION

Our results demonstrated that ABR deficiency could attenuate angiogenesis in ischaemic myocardium. These findings provide further mechanistic basis for enhancing baroreflex function in the treatment of MI.

Electrocardiogram-based predictors of sudden cardiac death in patients with coronary artery disease

Current recommendations on which patients with coronary artery disease (CAD) should be offered an implantable cardioverter defibrillator for the primary prevention of sudden cardiac death (SCD) rely heavily on the presence of depressed left ventricular ejection fraction. Because the majority of SCD victims with CAD have preserved left ventricular function, additional cardiac investigations are likely to play an increasing role in the risk stratification of CAD patients. A number of studies have demonstrated that certain parameters on the traditional 12-lead electrocardiogram (ECG) and other ECG-based investigations (such as signal-averaged ECG, heart rate turbulence, T-wave alternans) can provide important information on the underlying cardiac substrate abnormality that may predispose to ventricular arrhythmias and SCD. This article reviews some of the evidence for these ECG-based tests as predictors of SCD in patients with CAD and addresses their advantages and limitations.

Intensive management of electrical storm and incessant ventricular arrhythmias

Electrical storm (ES) is defined as ventricular tachycardia or ventricular fibrillation occurring at least three times in 24 h leading to hemodynamic unstable state that needs cardioversion or defibrillation. ES may cause fast hemodynamic impairment, leading to “low-perfusion” or “no perfusion” state of the organs, a vicious circle pointing toward cardiogenic shock, multi-organ failure, and pulseless electrical activity. ES in ICD patients may be a strong predictor of arrhythmic and nonarrhythmic death, as well as of rehospitalization. The first step is to start cardiopulmonary resuscitation to achieve complete hemodynamic stabilization to prevent the low-flow or no-flow state. The patient has to be transported to an intensive care unit for further specific treatment. The arrhythmia should be treated with specific antiarrhythmic agents, for example, amiodarone, lidocain and bretylium, and then all the reversible causes have to be detected and treated as fast as possible. Underlying heart disease determines the specific treatment such as coronary revascularization, mechanical circulatory and respiratory support, and ablation of the arrhythmic foci.

Endurance exercise training reduces cardiac sodium/calcium exchanger expression in animals susceptible to ventricular fibrillation

Aim: Increased sodium/calcium exchanger activity (NCX1, an important regulator of cardiomyocyte cystolic calcium) may provoke arrhythmias. Exercise training can decrease NCX1 expression in animals with heart failure improving cytosolic calcium regulation, and could thereby reduce the risk for ventricular fibrillation (VF). Methods: To test this hypothesis, a 2-min coronary occlusion was made during the last minute of exercise in dogs with healed myocardial infarctions; 23 had VF (S, susceptible) and 13 did not (R, resistant). The animals were randomly assigned to either 10-week exercise training (progressively increasing treadmill running; S n = 9; R n = 8) or 10-week sedentary (S n = 14; R n = 5) groups. At the end of the 10-week period, the exercise + ischemia test provoked VF in sedentary but not trained susceptible dogs. On a subsequent day, cardiac tissue was harvested and NCX1 protein expression was determined by Western blot. Results: In the sedentary group, NCX1 expression was significantly (ANOVA, P < 0.05) higher in susceptible compared to resistant dogs. In contrast, NCX1 levels were similar in the exercise trained resistant and susceptible animals. Conclusion: These data suggest that exercise training can restore a more normal NCX1 level in dogs susceptible to VF, improving cystolic calcium regulation and could thereby reduce the risk for sudden death following myocardial infarction.

Device therapy for the management of cardiac tachyarrhythmias

Implantation of devices that can terminate cardiac arrhythmias has increased rapidly over recent years. This article looks at the evidence base for using such devices in the primary and secondary prevention of sudden arrhythmic death, discusses who should have a device and examines the issues surrounding implantation. Recent advances in technology and the future direction of therapy are also reviewed.