Aravinda Thiagalingam

Effect of Lifestyle-Focused Text Messaging on Risk Factor Modification in Patients With Coronary Heart Disease: A Randomized Clinical Trial

IMPORTANCE Cardiovascular disease prevention, including lifestyle modification, is important but underutilized. Mobile health strategies could address this gap but lack evidence of therapeutic benefit. OBJECTIVE To examine the effect of a lifestyle-focused semipersonalized support program delivered by mobile phone text message on cardiovascular risk factors. DESIGN AND SETTING The Tobacco, Exercise and Diet Messages (TEXT ME) trial was a parallel-group, single-blind, randomized clinical trial that recruited 710 patients (mean age, 58 [SD, 9.2] years; 82% men; 53% current smokers) with proven coronary heart disease (prior myocardial infarction or proven angiographically) between September 2011 and November 2013 from a large tertiary hospital in Sydney, Australia. INTERVENTIONS Patients in the intervention group (n = 352) received 4 text messages per week for 6 months in addition to usual care. Text messages provided advice, motivational reminders, and support to change lifestyle behaviors. Patients in the control group (n=358) received usual care. Messages for each participant were selected from a bank of messages according to baseline characteristics (eg, smoking) and delivered via an automated computerized message management system. The program was not interactive. MAIN OUTCOMES AND MEASURES The primary end point was low-density lipoprotein cholesterol (LDL-C) level at 6 months. Secondary end points included systolic blood pressure, body mass index (BMI), physical activity, and smoking status. RESULTS At 6 months, levels of LDL-C were significantly lower in intervention participants, with concurrent reductions in systolic blood pressure and BMI, significant increases in physical activity, and a significant reduction in smoking. The majority reported the text messages to be useful (91%), easy to understand (97%), and appropriate in frequency (86%). [table: see text]. CONCLUSIONS AND RELEVANCE Among patients with coronary heart disease, the use of a lifestyle-focused text messaging service compared with usual care resulted in a modest improvement in LDL-C level and greater improvement in other cardiovascular disease risk factors. The duration of these effects and hence whether they result in improved clinical outcomes remain to be determined. TRIAL REGISTRATION anzctr.org.au Identifier: ACTRN12611000161921.

Importance of catheter contact force during irrigated radiofrequency ablation: evaluation in a porcine ex vivo model using a force-sensing catheter.

Effect of Ablation Electrode Contact Force. Introduction: Ablation electrode–tissue contact has been shown to be an important determinant of lesion size and safety during nonirrigated ablation but little data are available during irrigated ablation. We aimed to determine the importance of contact force during irrigated‐tip ablation.

Mobile Telephone Text Messaging for Medication Adherence in Chronic Disease: A Meta-analysis

IMPORTANCE Adherence to long-term therapies in chronic disease is poor. Traditional interventions to improve adherence are complex and not widely effective. Mobile telephone text messaging may be a scalable means to support medication adherence. OBJECTIVES To conduct a meta-analysis of randomized clinical trials to assess the effect of mobile telephone text messaging on medication adherence in chronic disease. DATA SOURCES MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, PsycINFO, and CINAHL (from database inception to January 15, 2015), as well as reference lists of the articles identified. The data were analyzed in March 2015. STUDY SELECTION Randomized clinical trials evaluating a mobile telephone text message intervention to promote medication adherence in adults with chronic disease. DATA EXTRACTION Two authors independently extracted information on study characteristics, text message characteristics, and outcome measures as per the predefined protocol. MAIN OUTCOMES AND MEASURES Odds ratios and pooled data were calculated using random-effects models. Risk of bias and study quality were assessed as per Cochrane guidelines. Disagreement was resolved by consensus. RESULTS Sixteen randomized clinical trials were included, with 5 of 16 using personalization, 8 of 16 using 2-way communication, and 8 of 16 using a daily text message frequency. The median intervention duration was 12 weeks, and self-report was the most commonly used method to assess medication adherence. In the pooled analysis of 2742 patients (median age, 39 years and 50.3% [1380 of 2742] female), text messaging significantly improved medication adherence (odds ratio, 2.11; 95% CI, 1.52-2.93; P < .001). The effect was not sensitive to study characteristics (intervention duration or type of disease) or text message characteristics (personalization, 2-way communication, or daily text message frequency). In a sensitivity analysis, our findings remained robust to change in inclusion criteria based on study quality (odds ratio, 1.67; 95% CI, 1.21-2.29; P = .002). There was moderate heterogeneity (I2 = 62%) across clinical trials. After adjustment for publication bias, the point estimate was reduced but remained positive for an intervention effect (odds ratio, 1.68; 95% CI, 1.18-2.39). CONCLUSIONS AND RELEVANCE Mobile phone text messaging approximately doubles the odds of medication adherence. This increase translates into adherence rates improving from 50% (assuming this baseline rate in patients with chronic disease) to 67.8%, or an absolute increase of 17.8%. While promising, these results should be interpreted with caution given the short duration of trials and reliance on self-reported medication adherence measures. Future studies need to determine the features of text message interventions that improve success, as well as appropriate patient populations, sustained effects, and influences on clinical outcomes.

Organization of Myocardial Activation During Ventricular Fibrillation After Myocardial Infarction Evidence for Sustained High-Frequency Sources

Background—Studies of ventricular fibrillation (VF) in small mammals have revealed localized sustained stationary reentry. However, studies in large mammals with surface mapping techniques have demonstrated only relatively short-lived rotors. The purpose of this study was to identify whether sustained high-frequency activation with low beat-to-beat variability was present at intramural sites in a postinfarct ovine model of VF. Methods and Results—VF was induced in 12 sheep 77±40 days after anterior myocardial infarction. Electrical activation was recorded with 20 multielectrode transmural plunge needles. Unipolar electrogram frequency content and local cycle duration variability were studied in 30-second recordings beginning 5 seconds after the onset of VF. Higher mean beat frequency was associated with lower SD of the cycle duration intervals (r=−0.91, P<0.001). The mean beat frequency and the SD of cycle duration intervals of the highest-frequency electrode were 8.8±2.0 Hz and 17±11 ms. In 3 cases, a region with regular activation throughout the recording was identified (SD of the cycle duration interval, 6.0±0.7 ms). Two of these sites and 67% of all sites with low local cycle duration variability were intramural. They occurred within regions with a high dominant frequency as determined by fast Fourier transform of the unipolar electrogram. Conclusions—Regions with the highest frequency of activation during VF were always associated with a low local cycle duration variability and usually intramural in this chronic infarct model. In a minority of cases, a region of stable, rapid, and very regular activation could be identified. These findings support the hypothesis that relatively stable periodic sources form a component of the mechanism of VF in this model.

Outcomes of Early Risk Stratification and Targeted Implantable Cardioverter-Defibrillator Implantation After ST-Elevation Myocardial Infarction Treated With Primary Percutaneous Coronary Intervention

BACKGROUND Methods to identify high-risk patients and timing of implantable cardioverter-defibrillator (ICD) therapy after ST-elevation myocardial infarction need further optimization. METHODS AND RESULTS We evaluated outcomes of early ICD implantation in patients with inducible ventricular tachycardia. Consecutive patients treated with primary percutaneous coronary intervention for acute ST-elevation myocardial infarction underwent early left ventricular ejection fraction (LVEF) assessment. Patients with LVEF >40% were discharged (group 1); patients with LVEF < or =40% underwent risk stratification with electrophysiological study. If no ventricular tachycardia was induced, patients were discharged without an ICD (group 2). If sustained monomorphic ventricular tachycardia (> or =200-ms cycle length) was induced, an ICD was implanted before discharge (group 3). Follow-up was obtained up to 30 months in all patients and up to 48 months in a subgroup of patients with LVEF < or =30% without an ICD. The primary end point was total mortality. Group 1 (n=574) had a mean LVEF of 54+/-8%; group 2 (n=83), 32+/-6%; and group 3 (n=32), 29+/-7%. At a median follow-up of 12 months, there was no significant difference in survival between the 3 groups (P=0.879), with mortality rates of 3%, 3%, and 6% for groups 1 through 3, respectively. In the subgroup of group 2 patients with LVEF < or =30% and no ICD (n=25), there was 9% mortality at a median follow-up of 25 months. In group 3, 19% had spontaneous ICD activation resulting from ventricular tachycardia. CONCLUSIONS Early ICD implantation limited to patients with inducible ventricular tachycardia enables a low overall mortality in patients with impaired LVEF after primary percutaneous coronary intervention for ST-elevation myocardial infarction.

Electroanatomic Mapping and Radiofrequency Ablation of Porcine Left Atria and Atrioventricular Nodes Using Magnetic Resonance Catheter Tracking

Background—The MRI-compatible electrophysiology system previously used for MR-guided left ventricular electroanatomic mapping was enhanced with improved MR tracking, an MR-compatible radiofrequency ablation system and higher-resolution imaging sequences to enable mapping, ablation, and ablation monitoring in smaller cardiac structures. MR-tracked navigation was performed to the left atrium (LA) and atrioventricular (AV) node, followed by LA electroanatomic mapping and radiofrequency ablation of the pulmonary veins (PVs) and AV node. Methods and Results—One ventricular ablation, 7 PV ablations, 3 LA mappings, and 3 AV node ablations were conducted. Three MRI-compatible devices (ablation/mapping catheter, torqueable sheath, stimulation/pacing catheter) were used, each with 4 to 5 tracking microcoils. Transseptal puncture was performed under x-ray, with all other procedural steps performed in the MRI. Preacquired MRI roadmaps served for real-time catheter navigation. Simultaneous tracking of 3 devices was performed at 13 frames per second. LA mapping and PV radiofrequency ablation were performed using tracked ablation catheters and sheaths. Ablation points were registered and verified after ablation using 3D myocardial delayed enhancement and postmortem gross tissue examination. Complete LA electroanatomic mapping was achieved in 3 of 3 pigs, Right inferior PV circumferential ablation was achieved in 3 of 7 pigs, with incomplete isolation caused by limited catheter deflection. During AV node ablation, ventricular pacing was performed, 3 devices were simultaneously tracked, and intracardiac ECGs were displayed. 3D myocardial delayed enhancement visualized node injury 2 minutes after ablation. AV node block succeeded in 2 of 3 pigs, with 1 temporary block. Conclusions—LA mapping, PV radiofrequency ablation, and AV node ablation were demonstrated under MRI guidance. Intraprocedural 3D myocardial delayed enhancement assessed lesion positional accuracy and dimensions.

Noncontact mapping of the left ventricle: insights from validation with transmural contact mapping.

It is not clear whether the noncontact electrograms obtained using the EnSite system in the left ventricle resemble most closely endocardial, intramural, or epicardial contact electrograms or a summation of transmural electrograms. This study compared unipolar virtual electrograms from the EnSite system with unipolar contact electrograms from transmural plunge needle electrodes using a 256‐channel mapping system. The study also evaluated the effects of differing activation sites (endocardial, intramural, or epicardial). A grid of 50–60 plunge needles was positioned in the left ventricles of eight male sheep. Each needle had four electrodes to record from the endocardium, two intramural sites, and the epicardium. Correlations between contact and noncontact electrograms were calculated on 32,242 electrograms. Noncontact electrograms correlated equally well in morphology and accuracy of timing with endocardial (0.88 ± 0.15), intramural (0.87 ± 0.15), epicardial (0.88 ± 0.15), and transmural summation contact electrograms (0.89 ± 0.14) during sinus rhythm, endocardial pacing, and epicardial pacing. There was a nonlinear relationship between noncontact electrogram accuracy as measured by correlation with the contact electrogram and distance from the multielectrode array (MEA): beyond 40 mm accuracy decreased rapidly. The accuracy of noncontact electrograms also decreased with increasing distance from the equator of the MEA. Virtual electrograms from noncontact mapping of normal left ventricles probably represent a summation of transmural activation. Noncontact mapping has similar accuracy with either endocardial or epicardial sites of origin of electrical activity provided the MEA is within 40 mm of the recording site. (PACE 2004; 27:570–578)

Electrophysiology-guided defibrillator implantation early after ST-elevation myocardial infarction.

BACKGROUND Sudden death risk is highest early after myocardial infarction (MI). Inducible ventricular tachycardia (VT) confers increased risk of spontaneous ventricular arrhythmias. OBJECTIVE The purpose of this study was to evaluate outcomes of electrophysiology (EP)-guided defibrillator implantation early after ST-elevation MI in patients with ejection fraction ≤40%. METHODS EP study was performed 9 days after MI (n = 360). Predischarge defibrillator was recommended if VT with cycle length ≥200 ms was induced with ≤4 extrastimuli (EP-positive [EP(pos)], n = 142). EP-negative (EP(neg)) patients were discharged without a defibrillator (n = 218). Primary endpoint was either sudden death or spontaneous ventricular arrhythmia. RESULTS Defibrillator was implanted in 71% of EP(pos) patients (median 21 days post-MI) and withheld in 94% of EP(neg) patients. At 2 years, primary endpoint was 4.3% in the EP(neg) group and 22% in the EP(pos) group (adjusted hazard ratio 0.46, P = .035, EP(neg) vs EP(pos)). Lack of a defibrillator in EP(pos) patients conferred a fourfold increased risk of sudden death (P = .014). EP(neg) patients without a defibrillator were at significantly lower risk for the primary endpoint than were EP(pos) patients without a defibrillator (adjusted HR 0.34, P = .011). Short inducible VT cycle length (200-230 ms) and use of the fourth extrastimulus identified patients at significant arrhythmic risk. CONCLUSION EP study performed early after MI identified patients at significant long-term arrhythmic risk at a critical time after MI in whom defibrillator implantation was protective. A large majority of patients (EP(neg); two thirds) were at significantly lower risk of arrhythmic events without a defibrillator in the long term.

Fiber architecture in remodeled myocardium revealed with a quantitative diffusion CMR tractography framework and histological validation.

BackgroundThe study of myofiber reorganization in the remote zone after myocardial infarction has been performed in 2D. Microstructural reorganization in remodeled hearts, however, can only be fully appreciated by considering myofibers as continuous 3D entities. The aim of this study was therefore to develop a technique for quantitative 3D diffusion CMR tractography of the heart, and to apply this method to quantify fiber architecture in the remote zone of remodeled hearts.MethodsDiffusion Tensor CMR of normal human, sheep, and rat hearts, as well as infarcted sheep hearts was performed ex vivo. Fiber tracts were generated with a fourth-order Runge-Kutta integration technique and classified statistically by the median, mean, maximum, or minimum helix angle (HA) along the tract. An index of tract coherence was derived from the relationship between these HA statistics. Histological validation was performed using phase-contrast microscopy.ResultsIn normal hearts, the subendocardial and subepicardial myofibers had a positive and negative HA, respectively, forming a symmetric distribution around the midmyocardium. However, in the remote zone of the infarcted hearts, a significant positive shift in HA was observed. The ratio between negative and positive HA variance was reduced from 0.96 ± 0.16 in normal hearts to 0.22 ± 0.08 in the remote zone of the remodeled hearts (p<0.05). This was confirmed histologically by the reduction of HA in the subepicardium from −52.03° ± 2.94° in normal hearts to −37.48° ± 4.05° in the remote zone of the remodeled hearts (p < 0.05).ConclusionsA significant reorganization of the 3D fiber continuum is observed in the remote zone of remodeled hearts. The positive (rightward) shift in HA in the remote zone is greatest in the subepicardium, but involves all layers of the myocardium. Tractography-based quantification, performed here for the first time in remodeled hearts, may provide a framework for assessing regional changes in the left ventricle following infarction.

Development of a set of mobile phone text messages designed for prevention of recurrent cardiovascular events.

Background: Supporting lifestyle change is an effective way of preventing recurrent events in people with cardiovascular disease (CVD). However, there is a need to develop innovative strategies that increase access to programmes for individuals at high risk of CVD. This study aimed to develop a bank of text messages designed to provide advice, motivation, and support for decreasing cardiovascular risk. Design: Iterative development process with mixed methods Methods: An initial bank of 120 text messages was drafted based on behaviour change techniques, guidelines, and input from clinicians and public health experts. A questionnaire was then administered to participants (n = 53) for evaluation of message content, usefulness, and language. To test the process of delivery, a pilot study was conducted using a specifically designed computer programme that delivered messages to multiple mobile phones according to a pre-specified schedule. Data were collected regarding message timing, delivery, and usefulness. Results: In the qualitative questionnaire, 92% of participants found the messages easy to understand and 86% found the messages contained useful information. Positive feedback was also obtained from the pilot study. Based on these results, together with suggestions provided, several messages were reworded and an additional 44 were written. The need for semi-personalization was also identified and a random set of 103 individualized messages was created. Conclusions: A final bank of 137 mobile telephone text messages designed to support behaviour change and decrease cardiovascular risk have been developed through a multistep iterative process. This provides a scientific approach for future developers of health-related text messages.