Recent trends in cardiac electrophysiology and catheter ablation in New Zealand.

BACKGROUND: Catheter ablation has rapidly become an integral part of the management of many arrhythmias. AIMS: To provide a history of clinical cardiac electrophysiology (EP) in New Zealand (NZ) and analysis of recent trends in EP procedures and catheter ablations across NZ, which has not previously been reported. METHODS: EP case type and volume were obtained from the EP databases from each of the four public and four private EP centres in NZ from 1 January 2014 to 31 December 2018. Procedure rates were expressed as per million population. RESULTS: A total of 7695 EP cases was performed, including 5929 (77%) in the public sector. Atrial fibrillation (AF) ablation was the most common procedure at 29%. EP procedure rates increased by 21% (to 353 per million in 2018), predominantly due to AF ablation rates increasing by 46%. Ventricular tachycardia ablation rates increased by 41% but only comprised 8% of procedures. There was a striking difference in the growth of EP procedure rates in the public compared to the private sector (4% vs 106%), as well as considerable differences in EP procedure and AF ablation rates across the public EP centres. NZ had lower ablation rates compared to countries with similar healthcare expenditure. CONCLUSION: There has been a substantial increase in EP procedure and AF ablation rates in NZ and international trends suggest this growth will continue. However, there is considerable variation in procedure rates and growth trends between EP centres, highlighting inequities in access within the country.

Comparison of electrographic changes, clinical features and outcomes in different variants of Takotsubo syndrome.

BACKGROUND: Dysfunction of the left ventricular (LV) apex (apical variant) is the most common form in Takotsubo syndrome (TS). Several less common non-apical variants have been described - mid-ventricular, basal and focal. We hypothesised that the clinical presentation, and electrocardiographic (ECG) findings may vary between apical and non-apical TS. METHODS: We prospectively identified 194 consecutive patients with TS presenting to Middlemore Hospital, Auckland and obtained clinical, echocardiography, coronary angiography, and long-term follow-up data. ECGs at admission and Day 1 were compared. RESULTS: Of 194 patients with TS, 168 (86.6%) had apical TS, and 26 (13.4%) non-apical TS (11 mid-ventricular TS, 5 basal TS, 10 focal TS). Apical TS patients had more significant LV systolic impairment (p = 0.001) and longer length of stay (p = 0.001). The extent of T-wave inversion (TWI) was similar for both groups on admission (p = 0.88). By Day 1 the extent of TWI was greater in apical TS group (median number of leads 5 vs. 1, p = 0.02). The change in QTc interval between admission and Day 1 was greater in apical TS group (29.7 ms vs. 2.77 ms, p < 0.001). Composite in-hospital complication rate was similar for both groups (13.7% vs. 15.4%, p = 0.77). CONCLUSIONS: Compared with non-apical variants, apical TS patients develop more extensive TWI and greater QT prolongation on ECG, and more significant LV systolic impairment, but in-hospital complications were similar. Clinicians should be aware that there is a sub-group of TS patients who have non-apical regional wall motion abnormalities and who don't develop ECG changes typical of the more common apical variant.

Ethnic variation in the trends of new implantable cardioverter defibrillator implants in New Zealand 2005-2019 (ANZACS-QI 63).

AIMS: Ethnic variation in implantable cardioverter defibrillator (ICD) implant rates have been reported internationally but have not previously been examined in New Zealand. This study examined trends in new ICD implants by ethnicity over an extended period. METHODS: All patients who received a new ICD implant between 2005 and 2019 were identified using the National Minimum Dataset, which collects information on all public hospital admissions in New Zealand. Ethnicity was classified using the following standard prioritisation: Maori, Pacific, Asian and European/Other. New ICD implant rates were analysed by ethnicity and age groups. RESULTS: A total of 5,514 new ICDs were implanted. New ICD implant rates increased from 41.4/million in 2005 to 98.2/million in 2019, an average increase of 5.4%/year (p<0.01). The highest age-standardised implant rates were among Maori, followed by Pacific, European/Other and Asian ethnicities. The largest increase was seen in Pacific people at 8.9%/year (p<0.01), followed by Maori and Asian people at 4.7%/year and 4.3%/year respectively (both p<0.01). In European/Other patients, ICD implant rates increased by 10.3%/year (p<0.01) between 2005 to 2012, then plateaued at -0.4%/year (p=0.71) between 2012 to 2019. By 2019, the age-standardised implant rates in Maori and Pacific people were two-fold higher than European/Others. CONCLUSION: There is marked ethnic variation in ICD implant rates in New Zealand. The higher implant rates in Maori and Pacific parallel known ethnic differences in rates of underlying cardiac disease. The more rapid increase in implant rates in these ethnic groups may represent more equitable treatment over time.

Unmasking latent preexcitation of a right-sided accessory pathway with intravenous adenosine after unexplained sudden cardiac arrest.

Intravenous adenosine is a simple test that can uncover latent preexcitation via an accessory pathway and is useful in the diagnostic workup of sudden cardiac arrest survivors without an identifiable cause. Latent preexcitation is usually associated with left free wall pathways but may also occur in right-sided accessory pathways with slow antegrade conduction. Although intermittent ECG evidence of preexcitation is generally considered a marker of low risk for sudden death, if this is due to an accessory pathway with long atrioventricular conduction time and short effective refractory period (rather than true intermittent conduction via the pathway), the risk for sudden death may be equal to those accessory pathways with manifest preexcitation.

Implantable cardioverter defibrillator and cardiac resynchronization therapy use in New Zealand (ANZACS-QI 33).

BACKGROUND: The ANZACS-QI Cardiac Implanted Device Registry (ANZACS-QI DEVICE) collects nationwide data on cardiac implantable electronic devices in New Zealand (NZ). We used the registry to describe contemporary NZ use of implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy (CRT). METHODS: All ICD and CRT Pacemaker implants recorded in ANZACS-QI DEVICE between 1 January 2014 and 31 December 2017 were analyzed. RESULTS: Of 1579 ICD implants, 1152 (73.0%) were new implants, including 49.0% for primary prevention and 51.0% for secondary prevention. In both groups, median age was 62 years and patients were predominantly male (81.4% and 79.2%, respectively). Most patients receiving a primary prevention ICD had a history of clinical heart failure (80.4%), NYHA class II-III symptoms (77.1%) and LVEF ≤35% (96.9%). In the secondary prevention ICD cohort, 88.4% were for sustained ventricular tachycardia or survived cardiac arrest from ventricular arrhythmia. Compared to primary prevention CRT Defibrillators (n = 155), those receiving CRT Pacemakers (n = 175) were older (median age 74 vs 66 years) and more likely to be female (38.3% vs 19.4%). Of the 427 (27.0%) ICD replacements (mean duration 6.3 years), 46.6% had received appropriate device therapy while 17.8% received inappropriate therapy. The ICD implant rate was 119 per million population with regional variation in implant rates, ratio of primary prevention ICD implants, and selection of CRT modality. CONCLUSION: In contemporary NZ practice three-quarters of ICD implants were new implants, of which half were for primary prevention. The majority met current guideline indications. Patients receiving CRT pacemaker were older and more likely to be female.

Ablation of Supraventricular Tachycardias From Concealed Left-Sided Nodoventricular and Nodofascicular Accessory Pathways.

BACKGROUND: Nodoventricular and nodofascicular accessory pathways (AP) are uncommon connections between the atrioventricular node and the fascicles or ventricles. METHODS: Five patients with nodofascicular or nodoventricular tachycardia were studied. RESULTS: We identified 5 patients with concealed, left-sided nodoventricular (n=4), and nodofascicular (n=1) AP. We proved the participation of AP in tachycardia by delivering His-synchronous premature ventricular contractions that either delayed the subsequent atrial electrogram or terminated the tachycardia (n=3), and by observing an increase in VA interval coincident with left bundle branch block (n=2). The APs were not atrioventricular pathways because the septal VA interval during tachycardia was <70 ms in 3, 1 had spontaneous atrioventricular dissociation, and in 1 the atria were dissociated from the circuit with atrial overdrive pacing. Entrainment from the right ventricle showed ventricular fusion in 4 out of 5 cases. A left-sided origin of the AP was suspected after failed ablation of the right inferior extension of atrioventricular node in 3 cases and by observing a VA increase with left bundle branch block in 2 cases. The nodofascicular and 3 of the nodoventricular AP were successfully ablated from within the proximal coronary sinus (CS) guided by recorded potentials at the roof of the CS, and 1 nodoventricular AP was ablated via a transseptal approach near the CS os. CONCLUSIONS: Left-sided nodofascicular and nodoventricular AP appear to connect the ventricles with the CS musculature in the region of the CS os. Mapping and successful ablation sites can be guided by recording potentials within or near the CS os.

Early direct current cardioversion or ablation for atrial fibrillation or atrial flutter and acute decompensated heart failure.

AIMS: Guidelines recommend initial rate control in haemodynamically stable patients with atrial fibrillation (AF) or atrial flutter (AFL) and acute decompensated heart failure (ADHF). There is limited data on early inpatient rhythm control. We investigated the outcomes of patients managed with early TOE-guided DC cardioversion (DCCV) or ablation. METHODS: We retrospectively analysed patients admitted to a single centre with AF or AFL and ADHF with LVEF≤40% that underwent inpatient TOE-guided DCCV or ablation. The primary endpoint was the one year composite outcome of mortality or rehospitalisation for heart failure. RESULTS: We identified 79 patients, including 33 with AF (32 DCCV, one ablation) and 46 with AFL (22 DCCV, 24 ablation). The primary endpoint occurred in 20%. One-year mortality was 2.5%. There were significantly fewer rehospitalisations for arrhythmia or heart failure with AFL-ablation compared to AFL-DCCV (21% vs 64%, p=<0.01). Clinical recurrence of AF or AFL was 43%. At follow-up LV assessment, LVEF>40% was found in 75% (p=<0.01), including 87% of patients without known cardiomyopathy and 82% of patients in sinus rhythm. CONCLUSION: Early inpatient DCCV or ablation for AF or AFL and ADHF had low mortality rates and rehospitalisation for heart failure with substantial improvement in LV function at follow-up.

Completeness of ANZACS-QI Cardiac Implanted DEVICE Registry and agreement with national datasets: ANZACS-QI 30.

AIMS: The ANZACS-QI Cardiac Implanted Device Registry (ANZACS-QI DEVICE) collects data on cardiac implantable electronic devices inserted in New Zealand. We evaluated completeness of data capture and quality of ANZACS-QI DEVICE in 2016. METHODS: Complete datasets within ANZACS-QI DEVICE, comprising DEVICE-PPM (permanent pacemakers) and DEVICE-ICD (implantable cardioverter defibrillators), from 1 January 2016 to 31 December 2016 were linked with the National Hospitalisation dataset (all New Zealand public hospital admissions). The total number of implants included procedures captured in either dataset. Variables assessed included age, gender, ethnicity, procedure type, implanting centre, admission and procedure date. RESULTS: DEVICE-PPM captured 85.9% of all PPM procedures (n=2,512). This was similar regardless of age, sex and ethnicity. In the 84.4% of procedures captured in both datasets, agreement was >97% for all variables except admission date (90.1%). DEVICE-ICD captured 81.3% of all ICD procedures (n=690). Capture was similar across age, sex and ethnicity groups. In the 76.8% of procedures captured in both datasets, agreement was >96% for all variables except admission date (90.6%). CONCLUSION: The ANZACS-QI DEVICE registry had a good capture rate and excellent agreement with the national dataset. This high concordance supports the use of both datasets for future research.

Age and hemodynamic responses to tilt testing in those with syncope of unknown origin.

OBJECTIVES: We sought to determine whether there are age-related differences in vasovagal syncope. BACKGROUND: In those with suspected vasovagal (neurocardiogenic) syncope, tilt testing demonstrates different hemodynamic responses. These responses may be age related, reflecting differing underlying pathophysiology. METHODS: Using a two-stage tilt protocol with glyceryl trinitrate (GTN) provocation, 505 consecutive syncopal patients were studied. Their baseline characteristics and hemodynamic responses during both early and tilt-induced collapse were analyzed. Hemodynamic responses were classified using the VAsovagal Syncope International Study (VASIS) criteria: mixed, cardioinhibition, severe cardioinhibition/asystole, pure vasodepression, chronotropic incompetence, and excessive heart rate rise. Multivariate regression analyses were performed to determine the associations of the baseline clinical characteristics (including age) and the tilt-induced hemodynamic responses. RESULTS: Thirty-three patients were unable to tolerate tilt testing. Age was independently associated with distinct responses during tilt. Chronotropic incompetence was predicted by increasing age (odds ratio [OR] 1.04, p < 0.0002). Younger age predicted an excessive heart rate rise (OR 0.97, p < 0.0005). Pure vasodepression was more common in the older group (>65 years; OR 29.5, p < 0.0001), whereas severe cardioinhibition was much less common in the older age group (OR 0.18, p < 0.0001). CONCLUSIONS: There appear to be distinct pathophysiologies underlying vasovagal syncope in different age groups. Young people appear to have excessive cardiac and autonomic responses to stress, whereas older patients appear to have a more generalized cardiovascular decline, with attenuated cardiac and autonomic responses to stress.

Cardiac pacemaker lead extraction using conventional techniques:a single centre experience.

BACKGROUND: New methods of lead extraction using laser sheath devices are under evaluation but these techniques are not available in the majority of centres and have cost implications. Furthermore, in the absence of comparative randomised trials, registry experience with new devices must be judged against contemporary data using conventional methods. We report a single centre series of pacemaker lead extraction using conventional methods. STUDY POPULATION: Attempted extraction of 165 leads during 95 procedures in 80 patients. Leads had been in place (dwell time) for a mean of 76 months (range 0.2-248.4 months). Indications for lead extraction: infection (41.1%), skin erosion (9.5%), advisory leads (12.6%), faulty leads (12.6%), other (24.2%). Extraction techniques: traction and/or locking stylets and dilator sheaths (89.7%), Byrd workstation (6.1%) and open thoracotomy (4.8%). RESULTS: Complete removal was achieved for 143 leads (86.7%), partial removal in 12 leads (7.3%) and 10 (6.1%) could not be removed. A shorter lead dwell time was associated with extraction success in both univariate (p=0.0004) and multivariate analyses (p<0.0001). There was a trend for a higher rate of success in atrial rather than ventricular leads (93.2% v 80.9%, p=0.052). Active fixation, patient gender, age and indication for lead extraction had no bearing on outcome. COMPLICATIONS: There were no deaths. Major complications occurred in 3 patients (3.2%): pericardial tamponade (1), pulmonary embolus (1) and stroke (1). Significant bleeding (requiring blood transfusion) occurred in 11 procedures (12%). CONCLUSIONS: Cardiac lead extraction using conventional methods has a high success rate of 86.7%. Success was significantly related to a shorter lead dwell time. Further prospective randomised trials are needed to compare traditional techniques with laser extraction both in terms of clinical outcome and cost-effectiveness.

Community detection of long QT syndrome with a clinical registry: an alternative to ECG screening programs?

BACKGROUND: Long QT syndrome (LQTS) prevalence is estimated at 4 of 10,000 based on community electrocardiogram (ECG) screening, about which there is disagreement regarding efficacy, accuracy, cost-effectiveness, and practicality. Family studies of autosomal dominant conditions such as LQTS have revealed 8-9 gene-positive family members per proband. OBJECTIVE: To evaluate a cardiac/genetic registry and family screening program as a tool to identify LQTS in the community. METHODS: Possible LQTS probands were referred to the New Zealand Cardiac Inherited Disease service. The registry was first established in the northern region (population 2.03 million), including central Auckland (population 0.46 million). After clinical evaluation, genetic testing and family cascade screening were initiated. Genotype-positive individuals were classified as definite LQTS, and others were classified as definite or probable LQTS by clinical and ECG criteria. RESULTS: One hundred twelve probands were identified (presentation: 7 sudden death, 82 cardiac event, 16 ECG abnormality, and 7 sudden death of a family member). Following cascade screening, 309 patients with LQTS were identified (248 definite and 61 probable). Two hundred twenty patients had LQTS-causing mutations identified (120 [55%] LQT1, 78 [35%] LQT2, 19 [9%] LQT3, 1 [0.5%] LQT 5, and 2 [1%] LQT7). Thus far, an average of 2.1 definitely or probably affected family members have been identified per proband. The community detection rate is 1.5 of 10,000 for the whole region and 2.2 of 10,000 in Auckland. CONCLUSIONS: A high level of community detection of LQTS is possible using a clinical registry. With adequate resourcing, this has the potential to be an effective alternative to community ECG screening.

Prospective, population-based long QT molecular autopsy study of postmortem negative sudden death in 1 to 40 year olds.

BACKGROUND: Retrospective investigation of sudden unexplained death in the young (SUDY) reveals that a high proportion is due to inherited heart disease. OBJECTIVE: The purpose of this study was to ascertain the diagnostic value of postmortem long QT (LQT) genetic analysis in a prospective study of SUDY victims 1-40 years old. METHODS: Denaturing high-performance liquid chromatography or direct sequencing of LQT genes 1, 2, 3, 5, and 6 was performed, in a National New Zealand protocol, in SUDY victims aged 1-40 years. RESULTS: Over 26 months (2006-2008), DNA was stored at autopsy from 52 victims of sudden unexpected death. Further testing revealed a diagnosis in 19 cases (poisoning 4, dilated cardiomyopathy 3, myocarditis 3, other 9). The remaining 33 cases underwent genetic testing (age at death 18 months-40 years, median 25 years). Eighteen (55%) died during sleep or at rest, and 7 (21%) died during light activity. Rare missense variants in LQT genes were found in 5 (15%) cases (confidence interval 3%-27%): T96R in KCNQ1 (11-year-old male), P968L in KCNH2 (32-year-old female), P2006A in SCN5A (34-year-old female), and R67H and R98W in KCNE1 (17- and 38-year-old females, respectively). Evidence of pathogenicity was provided by in vitro evidence (T96R), family phenotype-genotype co-segregation (R98W, P2006A), and/or previous reports (R67H, P968L, P2006A, R98W). Family cardiac investigation was possible in 23 (70%) families and revealed probable cause of death for 5 (15%) other victims (confidence interval 3%-27%). CONCLUSION: Most community SUDY occurs at rest or during light activity. A diagnostic rate of 15% supports the transition of LQT genetic autopsy, combined with family investigation, into routine medical practice.

Atrio-oesophageal fistula: an emergent complication of radiofrequency ablation.

A 72-year-old presented with features of sepsis, neurological sequelae and chest pain after a radiofrequency ablation for AF. Chest CT scan revealed a life-threatening condition not previously reported in emergency medicine journals.

First human demonstration of cardiac stimulation with transcutaneous ultrasound energy delivery: implications for wireless pacing with implantable devices.

OBJECTIVES: The purpose of this study was to evaluate the feasibility and safety of a novel technology that uses energy transfer from an ultrasound transmitter to achieve cardiac stimulation without the use of a pacing lead in humans. BACKGROUND: To overcome the limitations of pacemaker leads, a new technology enabling stimulation without the use of a lead is desirable. METHODS: A steerable bipolar electrophysiology catheter incorporating a receiver electrode into the tip and circuitry to convert ultrasound energy to electrical energy was inserted transvenously into the heart. An ultrasound transmitting transducer was placed on the chest wall with ultrasound gel. Ultrasound energy was amplitude-adjusted and transmitted at 313 to 385 kHz. The output waveform of the receiver electrode was monitored while the transmitter was moved on the chest wall to target the receiver. The ultrasound transmission amplitude was limited to a mechanical index of 1.9, the maximum allowed for ultrasound imaging systems. Ultrasound-mediated pacing with minimum voltage but consistent capture was obtained for 12 s. RESULTS: Twenty-four patients (48 +/- 12 years) were tested during or after completion of clinical electrophysiology procedures. A total of 80 pacing sites were tested (mean 3.3 sites/patient): 12 right atrial, 35 right ventricular, and 33 left ventricular (31 endocardial) sites. The transmit-to-receive distance was 11.3 +/- 3.2 cm (range 5.3 to 22.5 cm). Ultrasound-mediated pacing was achieved at all 80 test sites, with consistent capture at 77 sites. The mechanical index during pacing was 0.5 +/- 0.3 (range 0.1 to 1.5). The mean ultrasound-mediated capture threshold was 1.01 +/- 0.64 V. There was no adverse event related to ultrasound pacing. No patient experienced discomfort during pacing. CONCLUSIONS: The feasibility and safety of pacing usng ultrasound energy has been shown acutely.