Waveform optimization for internal cardioversion of atrial fibrillation.

INTRODUCTION: A novel atrial defibrillator was developed at the Royal Victoria Hospital in collaboration with the Nanotechnology and Integrated Bio-Engineering Centre, University of Ulster. This device is powered by an external pulse of radiofrequency energy and designed to cardiovert using low-tilt monophasic waveform (LTMW) and low-tilt biphasic waveform (LTBW), 12 milliseconds pulse width. This study compared the safety and efficacy of LTMW with LTBW for transvenous cardioversion of atrial fibrillation (AF). METHODS: Patients were anticoagulated with warfarin to maintain International Normalized Ratio between 2 and 3 for 4 weeks prior cardioversion. Warfarin international normalized ratio level was maintained in between 2 and 3 for 4 weeks prior cardioversion. St Jude's defibrillating catheter was positioned in the distal coronary sinus and right atrium and connected to the defibrillator via a junction box. After a test shock using a dummy load, the patient was cardioverted in a step-up progression from 50 to 300 V. Shock success was defined as return of sinus rhythm for 30 seconds or more. If cardioversion was unsuccessful at peak voltage, the patient was crossed over to the other arm of the waveform type and cardioverted at peak voltage. RESULTS: Thirty patients were randomized equally to LTBW and LTMW (15 each). Seven out of 15 patients (46%) cardioverted to sinus rhythm with LTBW, and 1 (6%) of 15, with LTMW (P = .035). Including crossover patients, 14 patients (46%) converted to sinus rhythm. After crossover, 4 patients were cardioverted with LTBW and 2 with LTMW. Overall mean voltage, current, and energy used for cardioversion were 270.53 ± 35.96 V, 3.68 ± 0.80 A, and 9.12 ± 3.73 J, respectively, and intracardiac impedance was 70.82 ± 13.46 Ω. For patients who were successfully cardioverted, mean voltage, current, energy, and intracardiac impedance were 268.28 ± 42.41 V, 3.52 ± 0.63 A, 8.51 ± 3.16 J, and 73.92 ± 12.01 Ω. There were no major adverse complications during the study. Cardiac markers measured postcardioversion were unremarkable. CONCLUSION: Low-tilt biphasic waveform was more efficacious for low-energy transvenous cardioversion of AF. A significant proportion of patients were successfully cardioverted to sinus rhythm with low energy. Radiofrequency-powered defibrillation can be safely used for transvenous cardioversion of AF.

Prognostic value of a multimarker approach for patients presenting to hospital with acute chest pain.

To evaluate the prognostic role of novel biomarkers for the risk stratification of patients admitted with ischemic-type chest pain, a prospective study of 664 patients presenting to 2 coronary care units with ischemic-type chest pain was conducted over 3 years beginning in 2003. Patients were assessed on admission for clinical characteristics, electrocardiographic findings, renal function, cardiac troponin T (cTnT), markers of myocyte injury (heart fatty acid-binding protein [H-FABP] and glycogen phosphorylase BB), neurohormonal activation (N-terminal-pro-brain natriuretic peptide [NT-pro-BNP]), hemostatic activity (fibrinogen and D-dimer), and vascular inflammation (high-sensitivity C-reactive protein, myeloperoxidase, matrix metalloproteinase-9, pregnancy-associated plasma protein-A, and soluble CD40 ligand). A >or=12-hour cTnT sample was also obtained. Myocardial infarction (MI) was defined as peak cTnT >or=0.03 microg/L. Patients were followed for 1 year from the time of admission. The primary end point was death or MI. Elevated fibrinogen, D-dimer, H-FABP, NT-pro-BNP, and peak cTnT were predictive of death or MI within 1 year (unadjusted odds ratios 2.5, 3.1, 5.4, 5.4, and 6.9, respectively). On multivariate analysis, H-FABP and NT-pro-BNP were selected, in addition to age, peak cTnT, and left ventricular hypertrophy on initial electrocardiography, as significant independent predictors of death or MI within 1 year. Patients without elevations of H-FABP, NT-pro-BNP, or peak cTnT formed a very low risk group in terms of death or MI within 1 year. A very high risk group had elevations of all 3 biomarkers. In conclusion, the measurement of H-FABP and NT-pro-BNP at the time of hospital admission for patients with ischemic-type chest pain adds useful prognostic information to that provided by the measurement of baseline and 12-hour cTnT.

Novel biomarkers in early diagnosis of acute myocardial infarction compared with cardiac troponin T.

AIMS: To evaluate the role of novel biomarkers in early detection of acute myocardial infarction (MI) in patients admitted with acute chest pain. METHODS AND RESULTS: A prospective study of 664 patients presenting to two coronary care units with chest pain was conducted over 3 years from 2003. Patients were assessed on admission: clinical characteristics, ECG (electrocardiogram), renal function, cardiac troponin T (cTnT), heart fatty acid binding protein (H-FABP), glycogen phosphorylase-BB, NT-pro-brain natriuretic peptide, D-dimer, hsCRP (high sensitivity C-reactive protein), myeloperoxidase, matrix metalloproteinase-9, pregnancy associated plasma protein-A, soluble CD40 ligand. A > or = 12 h cTnT sample was also obtained. MI was defined as cTnT > or = 0.03 microg/L. In patients presenting <4 h of symptom onset, sensitivity of H-FABP for MI was significantly higher than admission cTnT (73 vs. 55%; P = 0.043). Specificity of H-FABP was 71%. None of the other biomarkers challenged cTnT. Combined use of H-FABP and cTnT (either one elevated initially) significantly improved the sensitivities of H-FABP or cTnT (85%; P < or = 0.004). This combined approach also improved the negative predictive value, negative likelihood ratio, and the risk ratio. CONCLUSION: Assessment of H-FABP within the first 4 h of symptoms is superior to cTnT for detection of MI, and is a useful additional biomarker for patients with acute chest pain.

The role of biphasic shocks for transthoracic cardioversion of atrial fibrillation.

The modern generation of transthoracic defibrillators now employ impedance compensated biphasic waveforms. These new devices are superior to those with monophasic waveforms and practice is currently switching to biphasic defibrillators for the treatment of both ventricular and atrial fibrillation. However, there is no universal guideline for the use of biphasic defibrillators in direct current cardioversion of atrial fibrillation. This article reviews the use of biphasic defibrillation waveforms for transthoracic cardioversion of atrial fibrillation.