Richard E. Kerber

ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices: Summary Article A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/NASPE Committee to Update the 1998 Pacemaker Guidelines)

The current update of the ACC/AHA/NASPE Guidelines for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices includes several significant changes in the recommendations and in the supporting narrative portion. In this summary, we list the updated recommendations along with the respective

Part 8: Advanced Life Support 2010 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations

Part 8 : Advanced life support : 2010 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations

ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices: Summary Article

The current update of the ACC/AHA/NASPE Guidelines for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices includes several significant changes in the recommendations and in the supporting narrative portion. In this summary, we list the updated recommendations along with the respective 1998 recommendations, each one accompanied by a brief comment outlining the rationale for the changes, additions, or deletions. All new or revised recommendations are listed in the second column and appear in boldface type. References that support either the 1998 recommendations that have not changed or the new or revised recommendations are noted in parentheses at the end of each recommendation. The reader is referred to the full-text version of the guidelines posted on the American College of Cardiology (ACC), American Heart Association (AHA), and North American Society for Pacing and Electrophysiology (NASPE) World Wide Web sites for a more detailed exposition of the rationale for these changes. In addition to the recommendation changes listed here, this update includes an expanded section on the selection of pacemakers and implantable cardioverter-defibrillators (ICDs) that reflects the technical advances that have taken place since 1998. A brief expanded summary of pacemaker follow-up procedures is also new to these guidelines. For both of these …

Cardiac Hypertrophy Is Not a Required Compensatory Response to Short-Term Pressure Overload

BACKGROUND Cardiac hypertrophy is considered a necessary compensatory response to sustained elevations of left ventricular (LV) wall stress. METHODS AND RESULTS To test this, we inhibited calcineurin with cyclosporine (CsA) in the setting of surgically induced pressure overload in mice and examined in vivo parameters of ventricular volume and function using echocardiography. Normalized heart mass increased 45% by 5 weeks after thoracic aortic banding (TAB; heart weight/body weight, 8.3+/-0.9 mg/g [mean+/-SEM] versus 5. 7+/-0.1 mg/g unbanded, P<0.05). Similar increases were documented in the cell-surface area of isolated LV myocytes. In mice subjected to TAB+CsA treatment, we observed complete inhibition of hypertrophy (heart weight/body weight, 5.2+/-0.3 mg/g at 5 weeks) and myocyte surface area (endocardial and epicardial fractions). The mice tolerated abolition of hypertrophy with no signs of cardiovascular compromise, and 5-week mortality was not different from that of banded mice injected with vehicle (TAB+Veh). Despite abolition of hypertrophy by CsA (LV mass by echo, 83+/-5 mg versus 83+/-2 mg unbanded), chamber size (end-diastolic volume, 33+/-6 microL versus 37+/-1 microL unbanded), and systolic ejection performance (ejection fraction, 97+/-2% versus 97+/-1% unbanded) were normal. LV mass differed significantly in TAB+Veh animals (103+/-5 mg, P<0.05), but chamber volume (end-diastolic volume, 44+/-6 microL), ejection fraction (92+/-2%), and transstenotic pressure gradients (70+/-14 mm Hg in TAB+Veh versus 77+/-11 mm Hg in TAB+CsA) were not different. CONCLUSIONS In this experimental setting, calcineurin blockade with CsA prevented LV hypertrophy due to pressure overload. TAB mice treated with CsA maintain normal LV size and systolic function.

Automatic External Defibrillators for Public Access Defibrillation: Recommendations for Specifying and Reporting Arrhythmia Analysis Algorithm Performance, Incorporating New Waveforms, and Enhancing Safety A Statement for Health Professionals From the American Heart Association Task Force on Automatic External Defibrillation, Subcommittee on AED Safety and Efficacy

These recommendations are presented to enhance the safety and efficacy of AEDs intended for public access. The task force recommends that manufacturers present developmental and validation data on their own devices, emphasizing high sensitivity for shockable rhythms and high specificity for nonshockable rhythms. Alternative defibrillation waveforms may reduce energy requirements, reducing the size and weight of the device. The highest levels of safety for public access defibrillation are needed. Safe and effective use of AEDs that are widely available and easily handled by nonmedical personnel has the potential to dramatically increase survival from cardiac arrest.

Biphasic versus monophasic shock waveform for conversion of atrial fibrillation: the results of an international randomized, double-blind multicenter trial.

OBJECTIVES This study compared a biphasic waveform with a conventional monophasic waveform for cardioversion of atrial fibrillation (AF). BACKGROUND Biphasic shock waveforms have been demonstrated to be superior to monophasic shocks for termination of ventricular fibrillation, but data regarding biphasic shocks for conversion of AF are still emerging. METHODS In an international, multicenter, randomized, double-blind clinical trial, we compared the effectiveness of damped sine wave monophasic versus impedance-compensated truncated exponential biphasic shocks for the cardioversion of AF. Patients received up to five shocks, as necessary for conversion: 100 J, 150 J, 200 J, a fourth shock at maximum output for the initial waveform (200 J biphasic, 360 J monophasic) and a final cross-over shock at maximum output of the alternate waveform. RESULTS Analysis included 107 monophasic and 96 biphasic patients. The success rate was higher for biphasic than for monophasic shocks at each of the three shared energy levels (100 J: 60% vs. 22%, p < 0.0001; 150 J: 77% vs. 44%, p < 0.0001; 200 J: 90% vs. 53%, p < 0.0001). Through four shocks, at a maximum of 200 J, biphasic performance was similar to monophasic performance at 360 J (91% vs. 85%, p = 0.29). Biphasic patients required fewer shocks (1.7 +/- 1.0 vs. 2.8 +/- 1.2, p < 0.0001) and lower total energy delivered (217 +/- 176 J vs. 548 +/- 331 J, p < 0.0001). The biphasic shock waveform was also associated with a lower frequency of dermal injury (17% vs. 41%, p < 0.0001). CONCLUSIONS For the cardioversion of AF, a biphasic shock waveform has greater efficacy, requires fewer shocks and lower delivered energy, and results in less dermal injury than a monophasic shock waveform.

Energy, current, and success in defibrillation and cardioversion: clinical studies using an automated impedance-based method of energy adjustment.

The purposes of this study were two. First, we wanted to evaluate in patients a technique for automated adjustment of selected energy for defibrillation or cardioversion based on transthoracic impedance. Second, we wanted to define the relationship of peak current and shock success in various arrhythmias. Applying a previously validated method of predicting transthoracic impedance in advance of any shock, we modified defibrillators to automatically double the operator-selected energy if the predicted impedance exceeded 70 omega. Success rates of shocks given for ventricular and atrial arrhythmias from these modified energy-adjusting defibrillators were compared with success rates for shocks given from standard defibrillators. We prospectively collected data on 347 patients who received a total of 1009 shocks. Low-energy (100 J) shocks given to high-impedance (greater than or equal to 70 omega) patients had a poor success rate; in such high-impedance patients significant improvement in shock success rate was achieved by the energy-adjusting defibrillators. For example, when 100 J shocks were selected for high-impedance patients in ventricular fibrillation the energy-adjusting defibrillators achieved a shock success rate of 75%, whereas standard defibrillators achieved a shock success rate of only 36% (p less than .01). Similar improvements were seen for ventricular tachycardia and atrial fibrillation. Thus, automated energy adjustment based on transthoracic impedance is a beneficial approach to defibrillation and cardioversion. For ventricular fibrillation, atrial fibrillation, and atrial flutter there was a clear relationship between peak current and shock success.(ABSTRACT TRUNCATED AT 250 WORDS)

Part 6: Electrical therapies: Automated external defibrillators, defibrillation, cardioversion, and pacing: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care

The recommendations for electrical therapies described in this section are designed to improve survival from SCA and life-threatening arrhythmias. Whenever defibrillation is attempted, rescuers must coordinate high-quality CPR with defibrillation to minimize interruptions in chest compressions and to ensure immediate resumption of chest compressions after shock delivery. The high first-shock efficacy of newer biphasic defibrillators led to the recommendation of single shocks plus immediate CPR instead of 3-shock sequences that were recommended prior to 2005 to treat VF. Further data are needed to refine recommendations for energy levels for defibrillation and cardioversion using biphasic waveforms.

Transthoracic resistance in human defibrillation. Influence of body weight, chest size, serial shocks, paddle size and paddle contact pressure.

Successful defibrillation depends on delivery of adequate electrical current to the heart; one of the major determinants of current flow is transthoracic resistance (TTR). To study the factors influencing ITR, we prospectively collected data from 44 patients undergoing emergency defibrillation. Shocks of 94–450 J delivered energy were administered from specially calibrated Datascope defibrillators that displayed peak current flow, thereby permitting determination of TTR. Shocks were applied from standard (8.5-cm diameter) or large (13 cm) paddles placed anteriorly and laterally. First-shock TTR ranged from 15–143 Ω. There was a weak correlation between TTR and body weight (r = 0.45, p < 0.05) and a stronger correlation between TTR and chest width (r = 0.80, p < 0.01). Twenty-three patients who were defibrillated using standard 8.5-cm paddles had a mean TTR of 67 ± 36 Ω (± SD), whereas 21 patients who received shocks using paddle pairs with at least one large (13 cm) paddle had a 21% lower TTR of 53 ± 24 Ω (p = 0.05, unpaired t test). Ten patients received first and second shocks at the same energy level; TTR declined only 8%, from 52 ± 19 to 48 ± 16 Ω (p < 0.01, paired t test). In closed-chest dogs, shocks were administered using a spring apparatus that regulated paddle contact pressure against the thorax. Firmer contact pressure caused TTR to decrease 25%, from 48 + 22 to 36 ± 17 Ω (p < 0.01, paired t test). Thus, human TTR varies widely and is related most closely to chest size. TTR declines only slightly with a second shock at the same energy level. More substantial reductions in TTR and increases in current flow can be achieved by using large paddles and applying firm paddle contact pressure.

Delineation of the extent of coronary atherosclerosis by high-frequency epicardial echocardiography.

Postmortem studies suggest that coronary angiography does not always accurately delineate the extent of coronary-artery disease. We examined this problem in living human hearts by performing high-frequency epicardial echocardiography at the time of cardiac surgery. The ratio of the diameter of the lumen of the coronary artery to the thickness of its wall was used to quantify the severity of coronary lesions. In 11 patients with no angiographic evidence of coronary disease anywhere in the coronary tree, the mean (+/- SEM) ratio was 5.9 +/- 0.3. In 21 patients with angiographic disease at the site evaluated by echocardiography, the mean ratio was lower (2.3 +/- 0.2, P less than 0.05), reflecting encroachment into the arterial lumen by atherosclerotic plaque. In 15 patients with arterial segments that were angiographically normal but with arterial stenoses elsewhere in the coronary tree, the mean ratio was 4.1 +/- 0.3, with marked overlap with the values in the patients who had angiographic disease at the site of the echocardiographic evaluation. These results demonstrate, in living human hearts, that diffuse coronary atherosclerosis is often present when coronary angiography reveals only discrete stenoses. This finding suggests that coronary angiography may underestimate the severity and extent of coronary disease.