B. Shi

Implantable cardioverter-defibrillators: a long-term view.

Background:  No long‐term data on implantable cardioverter‐defibrillators (ICDs) exist in Australasia.

Correlation between vectorcardiographic measures and cardiac magnetic resonance imaging of the left ventricle in an implantable cardioverter defibrillator population.

BACKGROUND Measures of vectorcardiographic changes and LV remodelling have been associated with arrhythmic risk. However the correlation between the two modalities is not well characterised. METHODS We correlated spatial QRS-T angle and ventricular gradient with cardiac MRI derived LV global measures and scar pattern in 66 ICD recipients. RESULTS Spatial QRS-T angle was significantly larger in patients with ischaemic scar than those without scar (150°±22° vs. 119°±46°, p=0.01). Larger spatial QRS-T angle was also correlated with more depressed LV function, more dilated LV and larger LV mass. Ventricular gradient azimuth was significantly different between patients with no scar, non-ischaemic scar and ischaemic scar (20°±49° vs. 38°±62° vs. 65°±48°, p=0.009), but independent of spatial QRS-T angle and LV structure. CONCLUSIONS Spatial QRS-T angle and ventricular gradient are partially related to LV structural properties. Further investigation is warranted to examine their comparative and combined prognostic value in risk stratification of ventricular arrhythmias.

Cardiac troponin levels following implantable cardioverter defibrillation implantation and testing.

AIMS Previous studies have reported the defibrillation testing during implantable cardioverter defibrillator (ICD) implantation is associated with elevated cardiac biomarkers and ST-segment electrocardiogram (ECG) changes suggesting that shocks during testing may cause harm. However, the effects of testing have not been isolated from the implant procedure itself, where lead deployment may cause myocardial damage. This prospective study examined high sensitivity troponin T (hs-TnT) levels and ECG changes during ICD implanting alone, ICD implantation with testing and device testing as a stand-alone procedure. METHODS AND RESULTS We examined hs-TnT at baseline, and 6-8 h post procedure and 12 lead ECG at baseline, and 30 s, 5 min, and 10 min post right ventricle lead deployment and post defibrillation. There was no significant change in hs-TnT levels in a group of patients (n = 11) undergoing defibrillation testing alone, while hs-TnT was significantly elevated in patients undergoing implantation alone (n = 13, median increase 96%, P = 0.005) and in patients undergoing implantation and testing (n = 13, median increase 161%, P = 0.005). There was a significant correlation between the number of lead deployments and the percentage change in hs-TnT (r = -0.51, P = 0.01), but no correlation between either the number of shocks (r = 0.26, P = 0.25) or the total delivered energy (r = 0.24, P = 0.30) and percentage change in hs-TnT. CONCLUSION Implantation of ICD leads was associated with release of troponin, but we did not observe any evidence that ICD shocks alone cause myocardial injury.

An unmet need for implantable cardioverter-defibrillators in New Zealand.

AIMS This study examined the prior history of all patients presenting to the regional ambulance service with community cardiac arrest to determine what proportion of these patients had prior indications for implanted cardioverter-defibrillator (ICD) therapy. METHODS AND RESULTS We reviewed the medical history of all adult patients presenting to our regional ambulance service with cardiac arrest between 1 June 2007 and 31 May 2008 (n= 144). Patients were classified as either not having an ICD indication, having a possible ICD indication, or having an ICD indication by two electrophysiologists. Eighty-seven patients (60%) had no pre-existing indication for an ICD. Twenty-two patients (15%) had a possible indication for an ICD but required further investigation to confirm this. This group consisted of 6 patients (4%) with previously documented left ventricular ejection fraction <35%, but without a measurement in the last 12 months, 14 patients (10%) with heart failure (n= 10) or syncope (n= 4) without appropriate investigations, and 2 patients with an ICD indication but with co-morbidities that required further investigation. Thirty-five patients (24%) had a documented indication for an ICD. In 11 (8%) there was no evidence of a contraindication, in 3 (2%) alternative therapy was judged more appropriate, and in 21 (15%) contraindications to ICD implantation were also present. Addition of the 11 patients with an ICD indication and the 6 patients with a documented indication requiring updated measurement, 17 patients (12%) had a prior documented ICD indication but had not been referred for this therapy. CONCLUSIONS Our observation that 12% of sudden cardiac arrest patients had prior indications for an ICD demonstrates that there is an unmet need for ICDs in New Zealand.

Analysis of ECG Measures of Cardiac Repolarization in Relation to Arrhythmic Events in an Implantable Cardioverter Defibrillator Population

ECG‐derived measures of cardiac repolarization may have utility in risk prediction of future ventricular arrhythmia, and a range of different measures have been proposed. We compared time‐based, vectorcardiographic, and singular value decomposition (SVD) derived measures of repolarization to determine which was most predictive of appropriate therapy in an ICD population.

Standard 12-lead electrocardiography measures predictive of increased appropriate therapy in implantable cardioverter defibrillator recipients.

AIMS Identification of patients most likely to benefit from implantable cardioverter defibrillator (ICD) implant remains a complex challenge. This study aimed to investigate the utility of measures derived from standard 10 s 12-lead electrocardiogrphy (ECG) without complex signal processing in predicting appropriate therapy in an ICD population. METHODS AND RESULTS We examined 108 ICD patients for primary (n = 32) and secondary prevention (n = 76). Baseline clinical data and characteristics of QRS complex, T-wave, and heart rate from standard 12-lead ECG were examined and related to the occurrence of subsequent appropriate therapy. Over a mean follow-up of 29 ± 11 months, 44% of patients received appropriate therapy. Patients with depressed heart rate variability (HRV) (≤6.5%) were 2.68 [95% confidence interval (CI) 1.21-5.90, P = 0.015] times more likely to receive appropriate therapy than patients with HRV >6.5%. In patients with bundle branch block (BBB), large QRS dispersion of >39 ms was associated with 2.88 times risk (95% CI 1.24-6.71, P = 0.014) of experiencing appropriate therapy than those with QRS dispersion <39 ms. In patients without BBB, reduced maximum T-wave amplitude (<0.4 mV) were 3.82 times (95% CI 1.63-8.93, P = 0.002) more likely to receive appropriate therapy compared with those with maximum T-wave amplitude >0.4 mV. History of atrial arrhythmia [hazard ratio (HR) = 2.30, 95% CI 1.29-4.12, P = 0.005] and secondary prevention (HR = 2.55, 95% CI 1.14-5.71, P = 0.022) were also predictive of device therapy. CONCLUSION Measurements from standard 12-lead ECG were predictive of appropriate therapy in a heterogeneous ICD population. Incorporation of 12-lead ECG parameters such as these into risk stratification models may improve our ability to select patients for ICD implantation.

Long-term single-center comparison of ICD lead survival: Evidence for premature Linox lead failure

ICD lead failure is a potential source of significant morbidity and mortality. This study investigates the survival rates of Sprint Quattro, Endotak Reliance, and Linox ICD leads.