Matthew Webber

Interactions between heart rate variability and pulmonary gas exchange efficiency in humans

The respiratory component of heart rate variability (respiratory sinus arrhythmia, RSA) has been associated with improved pulmonary gas exchange efficiency in humans via the apparent clustering and scattering of heart beats in time with the inspiratory and expiratory phases of alveolar ventilation, respectively. However, since human RSA causes only marginal redistribution of heart beats to inspiration, we tested the hypothesis that any association between RSA amplitude and pulmonary gas exchange efficiency may be indirect. In 11 patients with fixed‐rate cardiac pacemakers and 10 healthy control subjects, we recorded R–R intervals, respiratory flow, end‐tidal gas tension and the ventilatory equivalents for carbon dioxide   and oxygen   during ‘fast’ (0.25 Hz) and ‘slow’ paced breathing (0.10 Hz). Mean heart rate, mean arterial blood pressure, mean arterial pressure fluctuations, tidal volume, end‐tidal CO2,  and   were similar between pacemaker and control groups in both the fast and slow breathing conditions. Although pacemaker patients had no RSA and slow breathing was associated with a 2.5‐fold RSA amplitude increase in control subjects (39 ± 21 versus 97 ± 45 ms, P < 0.001), comparable   (main effect for breathing frequency, F(1,19) = 76.54, P < 0.001) and   reductions (main effect for breathing frequency, F(1,19) = 23.90, P < 0.001) were observed for both cohorts during slow breathing. In addition, the degree of   (r=−0.36, P= 0.32) and   reductions (r=−0.29, P= 0.43) from fast to slow breathing were not correlated to the degree of associated RSA amplitude enhancements in control subjects. These findings suggest that the association between RSA amplitude and pulmonary gas exchange efficiency during variable‐frequency paced breathing observed in prior human work is not contingent on RSA being present. Therefore, whether RSA serves an intrinsic physiological function in optimizing pulmonary gas exchange efficiency in humans requires further experimental validation.

Improving Safety in Catheter Ablation for Atrial Fibrillation: A Prospective Study of the Use of Ultrasound to Guide Vascular Access

The most frequent complications of AF ablation (AFA) are related to vascular access, but there is little evidence as to how these can be minimized.

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.

066 MODIFICATION OF THE EUROPEAN HEART RHYTHM ASSOCIATION AF SYMPTOM SCORE IMPROVES DISCRIMINATIVE ABILITY: A VALIDATION STUDY

Introduction The European Heart Rhythm Association (EHRA) Score for symptoms in Atrial fibrillation (AF) was proposed in 2007 but thus far has not been validated, yet features in European Society of Cardiology 2010/2012 guidelines. Anecdotally, many clinicians feel the jump from class 2 (mild) to class 3 (severe) misses an important step (moderate) where intervention may be more likely to be considered. Table 1 Modified EHRA Class Symptoms Description 1 None N/A 2a Mild Normal daily activity not affected and symptoms not considered troublesome by patient 2b Moderate Normal daily activity not affected but patient troubled by symptoms 3 Severe Normal daily activity affected 4 Disabling Normal daily activity discontinued Methods Consecutive patients identified as having AF as their primary consultation reason for attending Heart Rhythm clinics at a large cardiovascular centre in the UK completed general (EQ5D) and AF-specific (AFEQT) Quality of Life (QoL) questionnaires. EHRA score was documented by the reviewing clinician, or retrospectively from clinical notes. Patients initially classified EHRA 2 were subsequently re-classified by two clinicians blinded to QoL scores as either 2a (mild: Normal daily activity not affected and symptoms not considered troublesome by patient) or 2b (moderate: Normal daily activity not affected but patient troubled by symptoms). Results QoL and symptom data was collected on 362 patients (59% Paroxysmal, 65% Male). Mean QoL scores by EHRA Class are shown in the table and ilustrated in the graph with degree of statistical difference (t test) shown at each grade boundary. There is an important stepwise progression in the AFEQT score as patients progress from EHRA Class 1–4 with a significant difference between 2a and 2b in all QoL measures. Figure 1 Table 2 EHRA Class (n) AFEQT overall Utility (by EQ5D) Visual analogue score 1 (149) 78.4 (±19.0) 0.85 (±0.21) 76.2 (±19.9) 2a (45) 70.9 (±19.8) 0.86 (±0.18) 75.6 (±19.9) 2 (99) 63.6 (±20.0) 0.81 (±0.17) 70.3 (±20.3) 2b (44) 58.3 (±17.3) 0.77 (±0.15) 65.1 (±20.1) 3 (90) 42.1 (±21.1) 0.69 (±0.27) 59.6 (±21.9) 4 (24) 31.3 (±18.6) 0.59 (±0.29) 46.9 (±25.9) Table 3 Modified EHRA class Symptoms Description 1 None N/A 2a Mild Normal daily activity not affected and symptoms not considered troublesome by patient 2b Moderate Normal daily activity not affected but patient troubled by symptoms 3 Severe Normal daily activity affected 4 Disabling Normal daily activity discontinued Conclusions Based on AFEQT score and EQ5D Visual Analogue scale this study provides the first validation of the EHRA score. The Modified Score improves discriminative ability and, importantly, health utility is significantly different at the 2a/2b and 2b/3 boundaries, where decisions about AF ablation are likely to be made. Based on utility; invasive treatment for patients graded 2b (or above) is likely to be more cost effective than those graded 2a (where the potential improvement to Class 1 is minimal). We recommend adoption of the modified system, and propose that EHRA 2b be considered the cut point for treatment decisions.

068 ALTHOUGH LIFE-THREATENING COMPLICATIONS ARE RARE, THE TRUE INCIDENCE OF VASCULAR-ACCESS RELATED BLEEDING AFTER ATRIAL FIBRILLATION ABLATION IS MUCH HIGHER THAN HAS PREVIOUSLY BEEN REPORTED

Introduction Catheter ablation (CA) is increasingly seen as an effective treatment for symptomatic atrial fibrillation (AF), particularly when antiarrhythmic drug therapy has failed. To perform CA several large-bore sheaths must be placed percutaneously into central veins. To prevent thromboembolism patients receive intravenous heparin±systemic anticoagulation with warfarin or an alternative agent. Perhaps unsurprisingly, the most commonly encountered complications from CA are vascular, with published rates of 2–5%. It is feared that some access complications may occur after hospital discharge, and so the overall incidence may be higher. There are no studies with systematic screening to include the post-discharge period. Table 1 BARC grade Description 0 No bleeding 1 Bleeding that is not actionable and does not cause the patient to seek unscheduled medical care 2 Any overt, actionable sign of haemorrhage (more than would be expected) that does not meet the criteria for Grades 3–5 but requi 3 Overt bleeding with haemoglobin drop of at least 3g/DL and/or requiring transfusion (3a); ¡Ý 5 g dl causing tamponade or requiring 4 CABG-related bleeding 5 Fatal bleeding Methods We prospectively studied consecutive cases undergoing CA at a single high-volume centre in the UK using a dedicated proforma to record vascular complications at the time of the CA and at hospital discharge. This was followed up 1 month later with a bespoke postal questionnaire. Results 143 consecutive patients underwent CA for AF over 5 months. An anatomical approach was used as standard. Where possible all sheaths were placed into a single, usually right femoral, vein. All patients received intra-procedural heparin to maintain an ACT of >300 s and 70% were performed on uninterrupted warfarin (with most of the rest receiving post-op dabigatran). Bleeding complications were classified according to BARC criteria (See table) and the time of reporting (Pre or post discharge). In hospital data was collected on all patients and questionnaire was returned by 77%. 32% of patients had vascular access complications, including 19 (13%) with minor (BARC 1) bleeding, 30 (21%) with a BARC 2 complication requiring further medical intervention, and 2 (1.4%) patients with BARC 3 bleeds. A further 11 (8%) patients suffered arterial puncture without sequelae and/or prolonged groin pain. 22 of the 51 bleeding complications (43%) were only detected on post-discharge screening. There were no fatal bleeds (BARC 5) or BARC 4 (CABG-related) bleeds. Most (26) oif the BARC 2 bleeds were managed with additional haemostasis although 2 required further imaging or resulted in repeat hospitalisation. Figure 1 Discussion The incidence of vascular access complications following CA for AF is much higher than has been previously reported although major complications are thankfully rare. Physicians should consider techniques that may reduce this risk, such as vascular ultrasound and we are currently evaluating this in the next phase of this study. Patients should be counselled about the true risks as part of the informed consent process. Trials must comprehensively screen for bleeding complications if they are to avoid under-reporting.