Implementation of Extracorporeal Membrane Oxygenation Without On-Site Cardiac Surgery or Perfusion Support: A Tale of Two County Hospitals

Patients with refractory respiratory and cardiac failure may present to noncardiac surgery centers. Prior studies have demonstrated that acute care surgeons, intensivists, and emergency medicine physicians can safely cannulate and manage patients receiving extracorporeal membrane oxygenation (ECMO). Harborview Medical Center (Harborview) and Hennepin County Medical Center (Hennepin) are both urban, county-owned, level 1 trauma centers that implemented ECMO without direct, on-site cardiac surgery or perfusion support. Both centers 1) use an ECMO specialist model staffed by specially trained nurses and respiratory therapists and 2) developed comparable training curricula for ECMO specialists, intensivists, surgeons, and trainees. Each program began with venovenous ECMO to provide support for refractory hypoxemic respiratory failure and subsequently expanded to venoarterial ECMO support. The coronavirus disease 2019 (COVID-19) pandemic created an impetus for restructuring, with each program creating a consulting service to facilitate ECMO delivery across multiple intensive care units (ICUs) and to promote fellow and resident training and experience. Both Harborview and Hennepin, urban county hospitals 1,700 miles apart in the United States, independently implemented and operate adult ECMO programs without involvement from cardiovascular surgery or perfusion services. This experience further supports the role of ECMO specialists in the delivery of extracorporeal life support.

Reducing occupational distress in veterinary medicine personnel with acceptance and commitment training: a pilot study

AIMS

To determine whether an educational programme targeting the reaction of veterinary personnel to difficult client interactions reduced burden transfer, stress and burnout in veterinary staff.

METHODS

Employees of three small-animal veterinary hospitals in the south-western United States of America were recruited and randomised to intervention (educational programme; n = 16) or control (no intervention; n = 18) groups. Participants of this randomised, parallel arms trial completed pre-programme assessment including the Burden Transfer Inventory (BTI), Perceived Stress Scale, and Copenhagen Burnout Inventory. Assessment was followed by two, group-format educational sessions, based on acceptance and commitment training, tailored to reducing reactivity to difficult veterinary client interactions (intervention group only). After training was completed, both groups were assessed using the same measures and the intervention participants provided use and acceptability ratings.

RESULTS

Intervention participants rated the programme as useful and appropriate, and reported that programme techniques were used a median of 43 (min 9, max 68) times during the 2 weeks prior to retesting. Relative to pre-programme scores, median post-programme scores for reaction (subscore of BTI) to difficult client interactions decreased in the intervention group (33 vs. 54; p = 0.047), but not in the control group (51 vs. 59; p = 0.210). Changes in median scores for stress and burnout from pre- to post-programme were non-significant for both groups.

CONCLUSIONS

This pilot and feasibility trial showed high rates of acceptability and use by participants, as well as promising reductions in burden transfer. A larger scale clinical trial with follow-up at extended time points is needed to more fully examine the efficacy of this novel programme.

CLINICAL RELEVANCE

Preliminary findings suggest this programme may be a useful approach to reducing occupational distress for individuals working in veterinary practice.

Relationships among owner consideration of euthanasia, caregiver burden, and treatment satisfaction in canine osteoarthritis

Although diagnosis of osteoarthritis (OA) has been recently linked to euthanasia in dogs, no prior work has examined the roles of caregiver burden or treatment satisfaction in this relationship. We expected that there would be an indirect effect of caregiver burden on the association between consideration of euthanasia and clinical signs of OA, but that this effect would be influenced by owner satisfaction. Cross-sectional online evaluations were completed by 277 owners of dogs with OA recruited through social media. Canine OA-related pain and functional impairment, owner consideration of euthanasia, caregiver burden, and satisfaction were examined. Relationships among OA-related pain and functional impairment, owner consideration of euthanasia, caregiver burden, and satisfaction were statistically significant (P 0.01 for all). Cross-sectional mediation analysis demonstrated a statistically significant indirect effect of caregiver burden on the relationship between consideration of euthanasia and OA-related clinical signs (bias-corrected 95% confidence interval [BC 95% CI], 0.001-0.009), which was significantly moderated by owner satisfaction (BC 95% CI, -0.003 to -0.0002). Findings align with prior work connecting canine OA to euthanasia. The current study extends past research to demonstrate that caregiver burden in the owner may be partially responsible for this relationship. The moderating role of owner satisfaction suggests that optimizing owner impressions of treatment and the veterinary team could attenuate these relationships, potentially decreasing the likelihood of premature euthanasia for dogs with OA.

Coronary Artery Disease in Chronic Kidney Disease: Need for a Heart-Kidney Team-Based Approach

Chronic kidney disease and coronary artery disease are co-prevalent conditions with unique epidemiological and pathophysiological features, that culminate in high rates of major adverse cardiovascular outcomes, including all-cause mortality. This review outlines a summary of the literature, and nuances pertaining to non-invasive risk assessment of this population, medical management options for coronary heart disease and coronary revascularisation. A collaborative heart-kidney team-based approach is imperative for critical management decisions for this patient population, especially coronary revascularisation; this review outlines specific periprocedural considerations pertaining to coronary revascularisation, and provides a proposed algorithm for approaching revascularisation choices in patients with end-stage kidney disease based on available literature.

A Pericardial Pin: Embolization of an Inferior Vena Cava Filter Strut Presenting as Acute Pericarditis

A 39-year-old man presented with chest pain initially attributed to viral pericarditis. He was found to have an embolized inferior vena cava filter strut that perforated the right ventricle. Inferior vena cava filter fracture and embolization should be considered in patients with chest pain and pericardial effusion. (Level of Difficulty: Beginner.)

Protamine-Induced Bradycardic Arrest in a Diabetic Patient

Protamine sulfate is a common reversal agent of systemic heparinization used during procedures. While the exact epidemiology of adverse events is unknown, prior allergic response to protamine-containing compounds or concomitant use of neutral protamine Hagedorn (NPH) insulin is associated with an increased risk of tachyarrhythmias and bradyarrhythmias. We present a case of a 68-year-old woman with no prior history of protamine sulfate intolerance that suffered bradycardic arrest following protamine infusion. Healthcare providers should recognize the potential for life-threatening tachyarrhythmias and bradyarrhythmias following protamine reversal, especially in diabetic patients at risk for autonomic dysfunction; medication and allergy review are encouraged prior to heparin reversal, especially in diabetic patients.

An international comparison of factors affecting quality of life among patients with congestive heart failure: A cross-sectional study

OBJECTIVE

To explore associations among twenty formal and informal, societal and individual-level factors and quality of life (QOL) among people living with congestive heart failure (CHF) in two settings with different healthcare and social care systems and sociocultural contexts.

SETTING AND PARTICIPANTS

We recruited 367 adult patients with CHF from a single heart failure clinic within two countries with different national social to healthcare spending ratios: Minneapolis, Minnesota, United States (US), and Nijmegen, Netherlands (NL).

DESIGN

Cross-sectional survey study. We adapted the Social Quality Model (SQM) to organize twenty diverse factors into four categories: Living Conditions (formal-societal: e.g., housing, education), Social Embeddedness (informal-societal: e.g., social support, trust), Societal Embeddedness (formal-individual: e.g., access to care, legal aid), and Self-Regulation (informal-individual: e.g., physical health, resilience). We developed a survey comprising validated instruments to assess each factor. We administered the survey in-person or by mail between March 2017 and August 2018.

OUTCOMES

We used Cantril's Self-Anchoring Scale to assess overall QOL. We used backwards stepwise regression to identify factors within each SQM category that were independently associated with QOL among US and NL participants (p<0.05). We then identified factors independently associated with QOL across all categories (p<0.05).

RESULTS

367 CHF patients from the US (32%) and NL (68%) participated. Among US participants, financial status, receiving legal aid or housing assistance, and resilience were associated with QOL, and together explained 49% of the variance in QOL; among NL participants, financial status, perceived physical health, independence in activities of daily living, and resilience were associated with QOL, and explained 53% of the variance in QOL.

CONCLUSIONS

Four formal and informal factors explained approximately half of the variance in QOL among patients with CHF in the US and NL.

Appropriateness of Cardiac Troponin Testing: Insights from the Use of TROPonin In Acute coronary syndromes (UTROPIA) Study

OBJECTIVE

Our objective was to examine the appropriateness of cardiac troponin (cTn) testing among patients with cTn increases.

METHODS

This is a planned secondary analysis of the Use of TROPonin In Acute coronary syndromes (UTROPIA, NCT02060760) observational cohort study. Appropriateness of cTn testing was adjudicated for emergency department patients with cTn increases >99^th percentile and analyzed using both contemporary and high-sensitivity (hs) cTnI assays according to sub-specialty, diagnoses, and symptoms.

RESULTS

Appropriateness was determined from 1272 and 1078 adjudication forms completed for 497 and 422 patients with contemporary and hs-cTnI increases, respectively. Appropriateness of cTnI testing across adjudication forms was 71.5% and 72.0% for cTnI and hs-cTnI, respectively. Compared with emergency physicians, cardiologists were less likely to classify cTnI orders as appropriate (cTnI: 79% vs 56%, P < .0001; hs-cTnI: 82% vs 51%, P < .0001). For contemporary cTnI, appropriateness of 95%, 70%, and 39% was observed among adjudication forms completed by cardiologists for type 1 myocardial infarction, type 2 myocardial infarction, and myocardial injury, respectively; compared with 90%, 86%, and 71%, respectively, among emergency physicians. Similar findings were observed using hs-cTnI. Discordance in appropriateness adjudication forms occurred most frequently in cases of myocardial injury (62% both assays) or type 2 myocardial infarction (cTnI 31%; hs-cTnI 23%).

CONCLUSIONS

Marked differences exist in the perception of what constitutes appropriate clinical use of cTn testing between cardiologists and emergency physicians, with emergency physicians more likely to see testing as appropriate across a range of clinical scenarios. Discordance derives most often from cases classified as myocardial injury or type 2 myocardial infarction.

Spontaneous Coronary Artery Dissection in a Healthy Woman after Initiating a High-Intensity Interval Training Workout Program

Although several risk factors are associated with spontaneous coronary artery dissection, strenuous activity is an uncommon risk factor for women. We report a case of a patient who developed spontaneous coronary artery dissection shortly after starting F45, a highly strenuous fitness program. As high-intensity exercise regimens become more mainstream, clinicians should more readily consider spontaneous coronary artery dissection in young patients with history of recent strenuous activity when presenting with symptoms concerning for acute coronary syndrome.

Predicting caregiver burden in general veterinary clients: Contribution of companion animal clinical signs and problem behaviors

Caregiver burden, found in many clients with a chronically or terminally ill companion animal, has been linked to poorer psychosocial function in the client and greater utilization of non-billable veterinary services. To reduce client caregiver burden, its determinants must first be identified. This study examined if companion animal clinical signs and problem behaviors predict veterinary client burden within broader client- and patient-based risk factor models. Data were collected in two phases. Phase 1 included 238 companion animal owners, including those with a sick companion animal (n=119) and matched healthy controls (n=119) recruited online. Phase 2 was comprised of 602 small animal general veterinary hospital clients (n=95 with a sick dog or cat). Participants completed cross-sectional online assessments of caregiver burden, psychosocial resources (social support, active coping, self-mastery), and an item pool of companion animal clinical signs and problem behaviors. Several signs/behaviors correlated with burden, most prominently: weakness, appearing sad/depressed or anxious, appearing to have pain/discomfort, change in personality, frequent urination, and excessive sleeping/lethargy. Within patient-based risk factors, caregiver burden was predicted by frequency of the companion animal's signs/behaviors (P<.01). Within client-based factors, potentially modifiable factors of client reaction to the animal's signs/behaviors (P=.01), and client sense of control (P<.04) predicted burden. Understanding burden may enhance veterinarian-client communication, and is important due to potential downstream effects of client burden, such as higher workload for the veterinarian. Supporting the client's sense of control may help alleviate burden when amelioration of the companion animal's presentation is not feasible.

Diagnostic Performance of High Sensitivity Compared with Contemporary Cardiac Troponin I for the Diagnosis of Acute Myocardial Infarction

BACKGROUND

We examined the diagnostic performance of high-sensitivity cardiac troponin I (hs-cTnI) vs contemporary cTnI with use of the 99th percentile alone and with a normal electrocardiogram (ECG) to rule out acute myocardial infarction (MI) and serial changes (deltas) to rule in MI.

METHODS

We included consecutive patients presenting to a US emergency department with serial cTnI onclinical indication. Diagnostic performance for acute MI, including MI subtypes, and 30-day outcomes were examined.

RESULTS

Among 1631 patients, MI was diagnosed in 12.9% using the contemporary cTnI assay and in 10.4% using the hs-cTnI assay. For ruling out MI, contemporary cTnI ≤99th percentile at 0, 3, and 6 h and a normal ECG had a negative predictive value (NPV) of 99.5% (95% CI, 98.6–100) and a sensitivity of 99.1% (95% CI, 97.4–100) for diagnostic and safety outcomes. Serial hs-cTnI measurements ≤99th percentile at 0 and 3 h and a normal ECG had an NPV and sensitivity of 100% (95% CI, 100–100) for diagnostic and safety outcomes. For ruling in MI, contemporary cTnI measurements had specificities of 84.4% (95% CI, 82.5–86.3) at presentation and 78.7% (95% CI, 75.4–82.0) with serial testing at 0, 3, and 6 h, improving to 89.2% (95% CI, 87.1–91.3) by using serial cTnI changes (delta, 0 and 6 h) &gt;150%. hs-cTnI had specificities of 86.9% (95% CI, 85.1–88.6) at presentation and 85.7% (95% CI, 83.5–87.9) with serial testing at 0 and 3 h, improving to 89.3% (95% CI, 87.3–91.2) using a delta hs-cTnI (0 and 3 h) &gt;5 ng/L.

CONCLUSIONS

hs-cTnI and contemporary cTnI assays are excellent in ruling out MI following recommendations predicated on serial testing and the 99th percentile with a normal ECG. For ruling in MI, deltas improve the specificity. ClinicalTrials.gov Identifier: NCT02060760

Discordance between ICD-Coded Myocardial Infarction and Diagnosis according to the Universal Definition of Myocardial Infarction

BACKGROUND

International Classification of Diseases (ICD) coding is the standard diagnostic tool for healthcare management. At present, type 2 myocardial infarction (T2MI) classification by the Universal Definition of Myocardial Infarction (MI) remains ignored in the ICD system. We determined the concordance for the diagnosis of MI using ICD-9 coding vs the Universal Definition.

METHODS

Cardiac troponin I (cTnI) was measured by both contemporary (cTnI) and high-sensitivity (hs-cTnI) assays in 1927 consecutive emergency department (ED) patients [Use of TROPonin In Acute coronary syndromes (UTROPIA) cohort] who had cTnI ordered on clinical indication. All patients were adjudicated using both contemporary and hs-cTnI assays. The Kappa index and McNemar test were used to assess concordance between ICD-9 code 410 and type 1 MI (T1MI) and type 2 MI (T2MI).

RESULTS

Among the 249 adjudicated MIs using the contemporary cTnI, only 69 (28%) were ICD-coded MIs. Of 180 patients not ICD coded as MI, 34 (19%) were T1MI and 146 (81%) were T2MI. For the ICD-coded MIs, 79% were T1MI and 21% were T2MI. A fair Kappa index, 0.386, and a McNemar difference of 0.0892 (P &lt; 0.001) were found. Among the 207 adjudicated MIs using the hs-cTnI assay, 67 (32%) were ICD coded as MI. Of the 140 patients not ICD coded as MI, 27 (19%) were T1MI and 113 (81%) were T2MI. For the ICD-coded MIs, 85% were T1MI and 15% T2MI. A moderate Kappa index, 0.439, and a McNemar difference of 0.0674 (P &lt; 0.001) were found.

CONCLUSIONS

ICD-9–coded MIs captured only a small proportion of adjudicated MIs, primarily from not coding T2MI. Our findings emphasize the need for an ICD code for T2MI.

Mechanism for pituitary adenylate cyclase-activating polypeptide-induced atrial fibrillation

INTRODUCTION

Pituitary adenylate cyclase-activating polypeptide (PACAP), which activates intracardiac postganglionic parasympathetic nerves, has a greater profibrillatory effect than vagal stimulation. However, the mechanism responsible for this is unclear.

METHODS AND RESULTS

We examined the effective refractory period (ERP), conduction time, and incidence of atrial fibrillation (AF) induced by a single premature extrastimulus at four atrial sites as well as the AF cycle length at 65 atrial sites in 12 autonomically decentralized, open chest, anesthetized dogs. These parameters were measured in the control condition, during cervical vagal stimulation, and after PACAP administration. PACAP shortened the ERP to a similar extent at all four sites. Vagal stimulation shortened the ERP primarily at the high right atrium, but not at the other three sites. Global dispersion of ERP and variation in the AF cycle length (P < 0.01) were less after PACAP than during vagal stimulation. A premature extrastimulus induced AF more frequently after PACAP than during vagal stimulation (P < 0.001). The ERP at the pacing site was shorter when AF was induced than when it was not induced regardless of the intervention and the pacing site. Conduction time following premature beats that induced AF was shorter after PACAP than during vagal stimulation (P < 0.01).

CONCLUSION

Global ERP shortening contributes to the greater profibrillatory effect of PACAP. In addition, the decreased conduction time following premature beats may be associated with AF induction in this model.

Life-threatening ventricular arrhythmias due to transient or correctable causes: high risk for death in follow-up

OBJECTIVES

This study evaluated the prognosis of patients resuscitated from ventricular tachycardia (VT) or ventricular fibrillation (VF) with a transient or correctable cause suspected as the cause of the VT/VF.

BACKGROUND

Patients resuscitated from VT/VF in whom a transient or correctable cause has been identified are thought to be at low risk for recurrence and often receive no primary treatment for their arrhythmias.

METHODS

In the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial, patients with a potentially transient or correctable cause of VT/VF were not eligible for randomization. The mortality of these patients was compared with the mortality of patients with a known high risk of recurrence of VT/VF in the AVID registry.

RESULTS

Compared with patients having high risk VT/VF, those with a transient or correctable cause for their presenting VT/VF were younger and had a higher left ventricular ejection fraction. These patients were more often treated with revascularization as the primary therapy, more commonly received a beta-blocker, less often required therapy for congestive heart failure and less commonly received either an antiarrhythmic drug or an implantable cardioverter defibrillator. Nevertheless, subsequent mortality of patients with a transient or correctable cause of VT/VF was no different or perhaps even worse than that of the primary VT/VF population.

CONCLUSIONS

Patients identified with a transient or correctable cause for their VT/VF remain at high risk for death. Further research is needed to define truly reversible causes of VT/VF. Meanwhile, these patients may require more aggressive evaluation, treatment and follow-up than is currently practiced.

Effects of pituitary adenylate cyclase-activating polypeptide on canine atrial electrophysiology

We hypothesized that pituitary adenylate cyclase-activating polypeptide (PACAP) activates intracardiac postganglionic parasympathetic nerves and has a different effect than cervical vagal stimulation. We measured effective refractory period (ERP) and conduction velocity at four atrial sites [high right atrium (HRA), low right atrium (LRA), high left atrium (HLA), and low left atrium (LLA)] and minimum atrial fibrillation (AF) cycle length at 12 atrial sites during cervical vagal stimulation and after PACAP in 26 autonomically decentralized, open-chest, anesthetized dogs. PACAP shortened ERP to a similar extent at all four sites (HRA, 58 +/- 2.0 ms; LRA, 60 +/- 6.3 ms; HLA, 68 +/- 11.5 ms; and LLA, 60 +/- 8.3 ms). Low- and high-intensity vagal stimulation shortened ERP at the HRA, but not in the other atrial sites (low-intensity stimulation: HRA, 64 +/- 4.0 ms; LRA, 126 +/- 5.1 ms; HLA, 110 +/- 9.5 ms; and LLA, 102 +/- 11.5 ms; high-intensity stimulation: HRA, 58 +/- 4.2 ms; and HLA, 101 +/- 4.0 ms). Conduction velocity was not altered by any intervention. Minimum AF cycle length after PACAP was similar in both atria but was shorter in the right atrium than in the left atrium during vagal stimulation. After atropine administration, no interventions changed ERP. These results suggest that PACAP shortens atrial refractoriness uniformly in both atria through activation of intrinsic cardiac nerves, not all of which are activated by cervical vagal stimulation.

Atrial fibrillation: a risk factor for increased mortality--an AVID registry analysis

Emerging evidence suggests that atrial fibrillation is not a benign arrhythmia. It is associated with increased risk of death. The magnitude of association is controversial and potential causes remain unknown. Patients in the registry of the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial form the basis for this report. Baseline variables, in particular the presence or absence of a history of atrial fibrillation/flutter, were examined in relation to survival. Multivariate Cox regression was used to adjust for differences in important baseline co-variables using 27 pre-selected variables. There were 3762 subjects who were followed for an average of 773+/-420 days; 1459 (39 %) qualified with ventricular fibrillation and 2303 (61 %) with ventricular tachycardia. A history of atrial fibrillation/flutter was present in 24.4 percent. There were many differences in baseline variables between those with and those without a history of atrial fibrillation/flutter. After adjustment for baseline differences, a history of atrial fibrillation/flutter remained a significant independent predictor of mortality, (relative risk=1.20; 95 % confidence intervals=1.03-1.40; p=0.020). Antiarrhythmic drug use, other than amiodarone or sotalol, was also a significant independent predictor of mortality (relative risk 1.34; 95 % confidence intervals 1.07-1.69, p=0.011. Atrial fibrillation/flutter is a significant independent risk factor for increased mortality in patients presenting with ventricular tachyarrhythmias. This risk may have been overestimated in previous studies that could not adjust for the proarrhythmic effects of antiarrhythmic drugs other than amiodarone or sotalol.

Endocardial stimulation of efferent parasympathetic nerves to the atrioventricular node in humans: optimal stimulation sites and the effects of digoxin

The purposes of this study were to identify optimal sites of stimulation of efferent parasympathetic nerve fibers to the human atrioventricular node via an endocardial catheter and to investigate the interaction between digoxin and vagal activation at the end organ.

METHODS

The ventricular rate was measured during atrial fibrillation, prior to and during parasympathetic nerve stimulation, in 8 patients taking digoxin and in 10 controls. High frequency electrical stimuli were delivered via an hexapolar or quadripolar electrode catheter, placed at the posteroseptal right atrium near the atrioventricular node (n=18 patients) or in the coronary sinus (n=12 of 18 patients). In 4 patients, stimulation was repeated after intravenous administration of 1 to 2 mg of atropine.

RESULTS

Nerve stimulation prolonged the R-R interval in all patients. Stimulation close to the posteroseptal right atrium led to maximal atrioventricular nodal slowing. The mean R-R intervals at baseline and during parasympathetic nerve stimulation (60 mA) from the posteroseptal right atrium and the proximal coronary sinus were 581+/-79 ms, 2440+/-466, and 900+/-228 ms respectively (p=0.0001). The response to nerve stimulation was greater in patients taking digoxin than in patients not taking the drug (p=0.02). Junctional rhythm occurred during nerve stimulation in 8/8 patients taking digoxin and 0/10 not taking the drug (p=0.0001). The response to stimulation was eliminated after atropine (p=0.01).

CONCLUSIONS

Parasympathetic nerves to the atrioventricular node were stimulated from the proximal coronary sinus as well as the posteroseptal right atrium. Stimulation at the posteroseptal right atrium resulted in the greatest response, and digoxin enhanced this response. The augmented response suggests that an interaction may exist between parasympathetic stimulation and digoxin at the end organ.

Patients at lower risk of arrhythmia recurrence: a subgroup in whom implantable defibrillators may not offer benefit. Antiarrhythmics Versus Implantable Defibrillator (AVID) Trial Investigators

OBJECTIVES

The goal of this study was to identify subgroups of arrhythmia patients who do not benefit from use of the implantable cardiac defibrillator (ICD).

BACKGROUND

Treatment of serious ventricular arrhythmias has evolved toward more common use of the ICD. Since estimates of the cost per year of life saved by ICD therapy vary from $25,000 to perhaps $125,000, it is important to identify patient subgroups that do not benefit from the ICD.

METHODS

Data for 491 ICD patients enrolled in the Antiarrhythmics Versus Implantable Defibrillators Study were used to create a hazards model relating baseline factors to time to first recurrent arrhythmia. The model was used to predict the hazard for recurrent arrhythmia among all trial patients. A priori cut points provided lower and higher recurrent arrhythmia risk strata. For each stratum the incremental years of life due to ICD versus antiarrhythmic drug therapy were calculated.

RESULTS

Factors that predicted recurrent arrhythmia were: ventricular tachycardia as the index arrhythmia, history of cerebrovascular disease, lower left ventricular ejection fraction, a history of any tachyarrhythmia before the index event and the absence of revascularization after the index event. Survival times (over a follow-up of three years) were identical in each arm of the lowest risk sextile (survival advantage 0.03 +/- 0.12 [se] years), while the survival advantage for patients above the first sextile was 0.27 +/- 0.07 (se) years (two-sided p = 0.05).

CONCLUSIONS

Patients presenting with an isolated episode of ventricular fibrillation in the absence of cerebrovascular disease or history of prior arrhythmia who have undergone revascularization or who have moderately preserved left ventricular function (left ventricular ejection fraction > 0.27) are not likely to benefit from ICD therapy compared with amiodarone therapy.

How to manage atrial fibrillation: an update on recent clinical trials

The latter half of the 1990s was a time of extraordinary progress in the understanding and management of atrial fibrillation (AF). Evidence that "AF begets AF" has generated considerable interest regarding the mechanisms responsible for this phenomenon and has sparked the development of new concepts in both pharmacologic and nonpharmacologic therapy. The recognition that, in some patients, AF is initiated and possibly maintained by atrial tachycardia originating in the pulmonary veins has challenged accepted notions regarding the mechanisms responsible for arrhythmia. New antiarrhythmic drugs, devices, ablation techniques, and pacing techniques have been developed and tested. Strategies for the use of existing therapies have been evaluated, and new indications for existing therapies are under consideration. This article reviews several studies published in 1999 and 2000 that addressed the mechanisms and the management of AF.

Impact of a guideline-based disease management team on outcomes of hospitalized patients with congestive heart failure

BACKGROUND

Congestive heart failure is the most common reason for hospitalization in the United States, and guidelines to improve the quality of care for patients with congestive heart failure have been developed. However, adherence is typically low. We hypothesized that a guideline-based care management team would result in greater quality and efficiency of care than guidelines alone.

METHODS

A faculty cardiologist and nurse care manager at an academic medical center reviewed each patient's data and made guideline-based recommendations. Hospital length of stay, total costs, and use of recommended guidelines were compared between 173 patients before team implementation but with available guidelines, 283 care-managed patients, and 126 concurrent non-care-managed patients.

RESULTS

Care-managed patients achieved higher rates of use of angiotensin-converting enzyme inhibitor than baseline or non-care-managed patients (95%, 60%, and 75%, respectively; P<.001), as well as increased adherence to guidelines for daily weight monitoring and assessment of left ventricular function. Hospital length of stay was lower (median, 3, 4, and 5 days, respectively; P<.001) as were costs of hospitalization (median, $2934, $3209, and $4830, respectively; P<.01). These differences persisted after adjustment for severity of illness.

CONCLUSIONS

When compared with dissemination of guidelines alone, an active care management approach was associated with significant improvements in quality and efficiency of care for hospitalized patients with congestive heart failure.

Efficacy and safety of moricizine in the maintenance of sinus rhythm in patients with recurrent atrial fibrillation

Maintenance of sinus rhythm is the primary goal of antiarrhythmic drug therapy for recurrent atrial fibrillation (AF). However, concern about proarrhythmic and negative inotropic effects has led to increasing reluctance to administer antiarrhythmic agents for this non-life-threatening arrhythmia. Moricizine is well tolerated in a wide variety of patients, and therefore, may be a safe and effective agent for treating AF. We retrospectively assessed the efficacy and safety of moricizine (mean dose 609 +/- 9 mg/day) in 85 consecutive patients with recurrent AF (2.6 +/- 0.5 years duration, 1.6 +/- 1 failed antiarrhythmic drugs). Structural heart disease was present in 69 (81%), but no recent myocardial infarct (< or =90 days) was present; mean left atrial size was 46 +/- 1 mm, and mean left ventricular ejection fraction was 0.51 +/- 0.01. Moricizine was discontinued because of unsuccessful direct-current cardioversion (n = 5) or clinically unacceptable side effects (n = 6); 6 patients developed transient side effects not requiring discontinuation. Of the 74 patients continuing therapy, 68% remained in sinus rhythm after 6 months, and 59% after 12 months. During a follow-up (21 +/- 2 months), there were neither deaths nor adverse effects requiring discontinuation of therapy. Thus, moricizine was effective, safe, and well tolerated in our patient cohort with AF.

Importance of atrial flutter isthmus in postoperative intra-atrial reentrant tachycardia

BACKGROUND

In survivors of congenital heart surgery, intra-atrial reentrant tachycardia (IART) often develops. Previous reports have emphasized the atriotomy scar as the central barrier around which a reentrant circuit may rotate but have not systematically evaluated the atrial flutter isthmus in such patients. We sought to determine the role of the atrial flutter isthmus in supporting IART in a group of postoperative patients with congenital heart disease.

METHODS AND RESULTS

Nineteen postoperative patients with IART underwent electrophysiological studies with entrainment mapping of the atrial flutter isthmus for determining postpacing intervals. Radiofrequency ablation was performed at the identified isthmus in an effort to create a complete line of block. Twenty-one IARTs were identified in 19 patients, with a mean tachycardia cycle length of 293+/-73 ms. The atrial flutter isthmus was part of the circuit in 15 of 21 (71. 4%). In the remaining 6 of 21, the ablation target zone was at sites near atrial incisions or suture lines. Ablation was successful in 19 of 21 (90.4%) IARTs and in 14 of 15 (93.3%) cases at the atrial flutter isthmus.

CONCLUSIONS

In most of our postoperative patients, the atrial flutter isthmus was part of the reentrant circuit. The fact that the atrial flutter isthmus is vulnerable to ablation suggests that whenever IART occurs late after repair of a congenital heart defect, the atrial flutter isthmus should be evaluated. These data support the theory that some form of conduction block between the vena cava is essential for the establishment of a stable substrate for the atrial flutter reentrant circuit.

Design and implementation of an inpatient disease management program

OBJECTIVE

To describe the development and implementation of an inpatient disease management program.

STUDY DESIGN

Prospective observational study.

PATIENTS AND METHODS

On the basis of opportunities for improving quality or efficiency of inpatient and emergency department care, 4 diagnoses, including congestive heart failure (CHF), gastrointestinal hemorrhage, community-acquired pneumonia and sickle-cell crisis were selected for implementation of a disease management program. For each diagnosis, a task force assembled a disease management team led by a "physician champion" and nurse care manager and identified opportunities for improvement through medical literature review and interviews with caregivers. A limited number of disease-specific guidelines and corresponding interventions were selected with consensus of the team and disseminated to caregivers. Physician and nurse team leaders were actively involved in patient care to facilitate adherence to guidelines.

RESULTS

For quarter 2 to 4 of 1997, there were improvements in angiotensin-converting enzyme inhibitor use, daily weight compliance, assessment of left ventricular function, hospital costs, and length of stay for care-managed patients with CHF. Differences in utilization-related outcomes persisted even after adjustment for severity of illness. For the other 3 diagnoses, the observational period was shorter (quarter 4 only), and hence preliminary data showed similar hospital costs and length of stay for care-managed and noncare-managed patients.

CONCLUSIONS

An interdisciplinary approach to inpatient disease management resulted in substantial improvements in both quality and efficiency of care for patients with CHF. Additional data are needed to determine the program's impact on outcomes of other targeted diagnoses.

Persistent T-wave changes after radiofrequency catheter ablation of an accessory connection (Wolff-parkinson-white syndrome) are caused by "cardiac memory"

BACKGROUND

The purpose of this study was to determine the incidence and origin of T-wave changes after ablation of an accessory atrioventricular connection (AC), which could either be a sign of damage to the coronary circulation or a result of persistent abnormal repolarization secondary to previously abnormal ventricular activation ("cardiac memory").

METHODS AND RESULTS

Ninety of 107 consecutive patients (33 women and 57 men, mean age 36 +/- 5 years) undergoing successful catheter ablation of an AC were studied. Patients with bundle branch block or more than 1 AC were excluded. Sixty-four patients had manifest preexcitation (group 1) and 26 had a concealed AC (group 2). Immediately after loss of preexcitation, 38 (59%) patients with a manifest AC showed T-wave abnormalities. In contrast, none of the patients with a concealed AC had T-wave abnormalities after ablation (P <.05). The T-wave changes (1) did not correlate with the number or duration of energy applications or with markers of tissue injury; (2) correlated with the location of the AC and the degree of preexcitation, respectively; and (3) completely resolved over a period of weeks to months. None of the patients had recurrence of preexcitation or tachycardia during a mean follow-up of 16 +/- 7 months.

CONCLUSIONS

T-wave changes after ablation are most likely caused by "cardiac memory" and are not a sign of myocardial or coronary injury.

Attitudes of faculty, housestaff, and medical students toward clinical practice guidelines

PURPOSE

To examine attitudes of faculty, housestaff, and medical students toward clinical practice guidelines.

METHOD

In a 1997 cross-sectional survey, a two-part, 26-item, self-administered questionnaire was mailed to all faculty, housestaff, and medical students in the department of internal medicine at Case Western Reserve University School of Medicine. The questionnaire asked for demographic information and attitudes toward clinical guidelines.

RESULTS

Of 379 persons surveyed, 254 (67%) returned usable questionnaires: 56% of the medical students, 70% of the housestaff, and 73% of the full-time faculty. Medical students reported learning about guidelines predominantly during clerkships in internal medicine (71%) and pediatrics (68%). Overall, the respondents agreed most strongly that guidelines are "useful for the care of common problems," and least strongly that guidelines are "difficult to apply to individual patients" and "reduce physician options in patient care." Faculty were more likely to consider guidelines a "good educational tool" and less likely than were medical students and housestaff to agree that they promote "cookbook medicine." Of 11 influences on clinical decision making, the three groups together rated practice guidelines eighth or ninth. The use of guidelines for academic investigations was rated most appropriate, overall. In terms of their appropriateness, faculty consistently rated the use of guidelines more favorably except for use in malpractice suits.

CONCLUSION

Faculty, housestaff, and medical students have significantly different perceptions of and attitudes toward clinical practice guidelines. Further studies are needed to explain the reasons for these differences. Considerable education and involvement must occur at all levels for practice guidelines to be successfully implemented and understood.

Reflex control of sympathetic activity during simulated ventricular tachycardia in humans

BACKGROUND

Ventricular tachyarrhythmias present a unique set of stimuli to arterial and cardiopulmonary baroreceptors by increasing cardiac filling pressures and decreasing arterial pressure. The net effect on the control of sympathetic nerve activity (SNA) in humans is unknown. The purpose of this study was to determine the relative roles of cardiopulmonary and arterial baroreceptors in controlling SNA and arterial pressure during ventricular pacing in humans.

METHODS AND RESULTS

Two experiments were performed in which SNA and hemodynamic responses to ventricular pacing were compared with nitroprusside infusion (NTP) in 12 patients and studied with and without head-up tilt or phenylephrine to normalize the stimuli to either the arterial or cardiopulmonary baroreceptors in 9 patients. In experiment 1, the slope of the relation between SNA and mean arterial pressure was greater during NTP (-4.7+/-1.4 U/mm Hg) than during ventricular pacing (-3.4+/-1.1 U/mm Hg). Comparison of NTP doses and ventricular pacing rates that produced comparable hypotension showed that SNA increased more during NTP (P=0.03). In experiment 2, normalization of arterial pressure during pacing resulted in SNA decreasing below baseline (P<0.05), whereas normalization of cardiac filling pressure resulted in a greater increase in SNA than pacing alone (212+/-35% versus 189+/-37%, P=0. 04). Conclusions--These data demonstrate that in humans arterial baroreflex control predominates in mediating sympathoexcitation during ventricular tachyarrhythmias and that cardiopulmonary baroreceptors contribute significant inhibitory modulation.

Beta-blocker use and survival in patients with ventricular fibrillation or symptomatic ventricular tachycardia: the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial

OBJECTIVES

To evaluate whether use of beta-adrenergic blocking agents, alone or in combination with specific antiarrhythmic therapy, is associated with improved survival in persons with ventricular fibrillation (VF) or symptomatic ventricular tachycardia (VT).

BACKGROUND

The ability of beta-blockers to alter the mortality of patients with VF or VT receiving contemporary medical management is not well defined.

METHODS

Survival of 1,016 randomized and 2,101 eligible, nonrandomized patients with VF or symptomatic VT followed in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial through December 31, 1996 was assessed using Cox proportional hazards analysis.

RESULTS

The 817 (28%) patients discharged from hospital receiving beta-blockers had less ventricular dysfunction, fewer symptoms of heart failure and a different pattern of medication use compared with patients not receiving beta-blockers. Before adjustment for important prognostic variables, beta-blockade was not significantly associated with survival in randomized or in eligible, nonrandomized patients treated with specific antiarrhythmic therapy. After adjustment, beta-blockade remained unrelated to survival in randomized or in eligible, nonrandomized patients treated with amiodarone alone (n = 1142; adjusted relative risk [RR] = 0.96; 95% confidence interval [CI] 0.64-1.45; p = 0.85) or a defibrillator alone (n = 1347; adjusted RR = 0.88; 95% CI 0.55 to 1.40; p = 0.58). In contrast, beta-blockade was independently associated with improved survival in eligible, nonrandomized patients who were not treated with specific antiarrhythmic therapy (n = 412; adjusted RR = 0.47; 95% CI 0.25 to 0.88; p = 0.018).

CONCLUSIONS

Beta-blocker use was independently associated with improved survival in patients with VF or symptomatic VT who were not treated with specific antiarrhythmic therapy, but a protective effect was not prominent in patients already receiving amiodarone or a defibrillator.

Characterization of sinoatrial parasympathetic innervation in humans

INTRODUCTION

The response to sinoatrial parasympathetic nerve stimulation (shortened atrial refractoriness) was used to determine the atrial distribution of these nerve fibers in humans. We hypothesized that, in humans, parasympathetic nerves that innervate the sinoatrial node also innervate the right atrium and that the greatest density of innervation is near the sinoatrial nodal fat pad.

METHODS AND RESULTS

Temporary epicardial wire electrodes were sutured in pairs in the sinoatrial nodal fat pad, high right atrium, and right ventricle by direct visualization during coronary artery bypass surgery in nine patients. Appropriate electrode placement was confirmed by electrically stimulating the fat pad in the operating room to prolong sinus cycle length by 50%. Experiments were performed in the electrophysiology laboratory 1 to 5 days after surgery. Programmed atrial stimulation was performed via an endocardial electrode catheter advanced to the right atrium. The catheter tip electrode was moved in 1-cm concentric zones around the epicardial wires by fluoroscopic guidance. Atrial refractoriness was determined in the presence and absence of sinoatrial parasympathetic nerve stimulation at each catheter site. In 8 of 9 patients, parasympathetic nerve stimulation reproducibly prolonged sinus cycle length by 50%. There was no effect on AV nodal conduction (no prolongation of PR interval) and no change in AV nodal refractoriness. Atrial effective refractory periods reproducibly shortened in response to parasympathetic nerve stimulation in 1-cm zones up to 3 cm surrounding the fat pad, by a mean (+/- SEM) of 26.6+/-4.3 msec (zone 1), 11.4+/-1.8 msec (zone 2), and 10.0+/-2.5 msec (zone 3), respectively (P = 0.0001). At distances > 3 cm from the fat pad, the effective refractory period did not shorten.

CONCLUSION

Stimulation of parasympathetic nerves that innervate the sinoatrial node shortened atrial refractoriness in humans.

New evidence that AV node slow pathway conduction directly influences fast pathway function

INTRODUCTION

Shortening of the AV node fast pathway effective refractory period (ERP) following successful slow pathway ablation may be a nonspecific effect of energy application at the AV junction or may be due to elimination of a direct effect of slow pathway conduction on the fast pathway.

METHODS AND RESULTS

Twenty-six consecutive patients (20 women and 6 men; mean age 45 +/- 3 years) with typical AV nodal reentrant tachycardia who underwent successful slow pathway ablation (defined as complete elimination of dual AV node physiology) were studied. The fast pathway ERP (at a drive train cycle length of 600 msec) was determined prior to ablation (baseline) and following unsuccessful and successful ablation attempts. Successful slow pathway ablation shortened the fast pathway ERP significantly (317 +/- 9 msec; P < 0.001) compared to baseline (386 +/- 12 msec), whereas unsuccessful ablations had no effect (376 +/- 11 msec). Sinus cycle length, the AH interval, and blood pressure were unchanged following successful ablation. Shortening of the fast pathway ERP did not correlate with the number of energy applications or with two measures of the proximity between the slow and the fast pathway.

CONCLUSION

These results support the hypothesis that shortening of the fast pathway ERP following slow pathway ablation is due to elimination of a direct effect of slow pathway conduction on fast pathway function rather than a nonspecific effect of repeated energy delivery at the AV junction.

Right ventricular arrhythmia in the absence of arrhythmogenic dysplasia: MR imaging of myocardial abnormalities

PURPOSE

To evaluate right ventricular abnormalities with magnetic resonance (MR) imaging in patients with arrhythmia but without arrhythmogenic dysplasia.

MATERIALS AND METHODS

In 53 patients being evaluated for right ventricular arrhythmia and 15 control subjects, MR imaging was performed to evaluate fixed thinning, fatty replacement, or reduced systolic wall thickening or motion. A diagnosis of idiopathic right ventricular outflow tract tachycardia or indeterminate was assigned for each patient, and the severity of arrhythmia was categorized.

RESULTS

Right ventricular abnormalities were revealed in 32 (60%) of the 53 patients: fixed thinning in 27 (84%), fatty replacement in eight (25%), and reduced wall thickening or motion in 31 (97%). Right ventricular abnormalities were found in 35 (76%) of 46 patients with idiopathic right ventricular outflow tract tachycardia and in seven (39%) of 18 patients with indeterminate diagnoses (P = .022).

CONCLUSION

Mild right ventricular abnormalities are likely sources for arrhythmias, even in the absence of arrhythmogenic right ventricular dysplasia.

An increase in sinus rate following radiofrequency energy application in the posteroseptal space

An increase in sinus rate has been previously described in patients with AV node reentry (AVNRT) following successful AV node modification. This increase could either be a specific sign of elimination of slow pathway conduction or it could be a consequence of energy application in the posteroseptal area. Thus, we compared the changes in sinus cycle length following successful slow pathway ablation (defined as complete elimination of dual AV node physiology) in patients having AVNRT with those in patients undergoing successful ablation of a posteroseptal atrioventricular accessory connection. Twenty five patients (16 women and 9 men, mean age 41 +/- 4 years) with typical AVNRT (cycle length 378 +/- 12 ms) and 29 patients (16 women and 13 men, age 34 +/- 5 years) with an accessory connection (17 manifest and 12 concealed) were studied. The electrophysiology study was performed during sedation with Fentanyl and Midazolam. The mean number of energy applications was 3 +/- 1 for successful slow pathway ablation and 4 +/- 1 for successful ablation of the accessory connection (p:NS). Following the successful energy application, the sinus cycle length decreased significantly 776 ms at baseline to 691 ms in patients with AVNRT. Following successful ablation of the posteroseptal AC, sinus cycle length decreased from 755 ms at baseline to 664 ms (p < 0.05 in both groups [difference between groups not significant]). The decrease in sinus cycle length did not correlate with the number of RF energy applications required for successful ablation or the total energy delivered. In conclusion, ablation of the AV node slow pathway and a posteroseptal accessory connection results in similar increases in the sinus rate. Thus, the increase in sinus rate is probably due to energy application in the posteroseptal space, possibly due to concomitant destruction of vagal inputs, and it is not specific for elimination of slow pathway conduction.

Favorable results of implantable cardioverter-defibrillator implantation in patients older than 70 years

BACKGROUND

The clinical results of implantable cardioverter-defibrillator (ICD) implantation in the elderly have received limited documentation. As the longevity of the U.S. population has increased, so has the need for ICD implantation in the elderly. We evaluated the efficacy and outcome of ICD implantation in elderly patients (>70 years) compared with younger patients.

METHODS

The case records of all consecutive patients who underwent ICD implantation at our institution between 1986 and 1994 were reviewed. Of a total of 238 patients, 78 patients were 70 years of age or older and 160 patients were younger than 70 years of age.

RESULTS

The mean age of the younger group was 58 years and that of the elderly group was 74 years. There were no statistical differences in the presence of coronary artery disease, left ventricular systolic function, the inducibility of arrhythmias, or the history of sudden cardiac death. The hospital morbidity rate was similar in both groups (6.9% in the younger group and 7.7% in the elderly group; p = not significant). The operative mortality rate was 1.9% for the younger group and 1.3% for the elderly group (p = not significant). At a mean follow-up of 33 +/- 26 months, Kaplan-Meier survival curves demonstrated similar survival rates, with 93%, 82%, and 65% of the patients alive at 1, 3, and 6 years, respectively.

CONCLUSIONS

Implantable cardioverter-defibrillator implantation was equally effective in the treatment of patients older than 70 years as in younger patients. No differences in theoretic survival or morbidity were observed.

Systolic blood pressure at rest, not the degree of beta blockade, predicts the result of follow-up tilt-table testing for vasovagal syncope

Tilt-table testing after therapy with beta blockade is frequently used to predict clinical success. This study found that heart rate and blood pressure reductions after beta-blocker therapy did not predict the results of the follow-up tilt-table test, but low blood pressure at rest before the initial test predicts failure of this therapy.

Tachycardia-induced cardiomyopathy secondary to right ventricular outflow tract ventricular tachycardia: improvement of left ventricular systolic function after radiofrequency catheter ablation of the arrhythmia

INTRODUCTION

Several reports describe development of cardiomyopathies secondary to supraventricular tachycardia. Few reports have described cardiomyopathies secondary to ventricular tachycardia.

METHODS AND RESULTS

We describe a patient who presented with dilated cardiomyopathy and repetitive nonsustained monomorphic ventricular tachycardia. Cardiac catheterization showed hemodynamically insignificant coronary artery disease. Radiofrequency ablation of a right ventricular outflow tract ventricular tachycardia resulted in improvement of the left ventricular systolic function and resolution of heart failure symptoms.

CONCLUSIONS

This report suggests that right ventricular outflow tract ventricular tachycardia may cause reversible tachycardia-induced cardiomyopathy.

Mechanisms of heart rate and arterial blood pressure control: implications for the pathophysiology of neurocardiogenic syncope

Neurocardiogenic syncope is a general term that describes syncope resulting from altered autonomic activity, as manifested by abnormal regulation of peripheral vascular resistance and heart rate. Although there has been great interest in the contribution of heart rate to this form of syncope, the peripheral circulation plays the dominant role in the induction of neurocardiogenic syncope in most patients. We review in this brief article the physiology of cardiovascular reflexes, which are important for short-term arterial pressure control, and their potential contribution to the pathophysiology of neurocardiogenic syncope. This type of syncope represents a profound failure of the normal mechanisms for short-term regulation of arterial pressure. Any therapeutic strategies for the management of neurocardiogenic syncope must deal with alterations in vascular control, which contribute to its pathogenesis.

Current-based transthoracic defibrillation

This study examines in a prospective, multicenter trial the feasibility and advantage of current-based, transthoracic defibrillation. Current-based, damped, sinusoidal waveform shocks of 18, 25, 30, 35, or 40 amperes (A) were administered beginning with 25 A for polymorphic ventricular tachycardia (VT) and ventricular fibrillation (VF) or 18 A for monomorphic VT; success rates were compared with those of energy-based shocks beginning at 200 J for VF/polymorphic VT and 100 J for VT. The current-based shocks were delivered from custom-modified defibrillators that determined impedance in advance of any shock using a "test-pulse" technique; the capacitor then charged to the exact energy necessary to deliver the operator-selected current against the impedance determined by the defibrillator. Three hundred sixty-two patients received > 1 shock for VF, polymorphic VT, or monomorphic VT: 569 current- based shocks and 420 energy-based shocks. Current-based shocks of 35/40 A achieved success rates of up to 74% for VF/polymorphic VT; 30 A shocks terminated 88% of monomorphic VT episodes. Energy-based shocks of 300 J terminated 72% of VF/polymorphic VT; 200-J shocks terminated 89% of monomorphic VT. We could not demonstrate a significant increase in the success rate of current-based shocks over energy-based shocks for patients with high transthoracic impedance; this may be due to inadequate sample size. Thus, current-based defibrillation is clinically feasible and effective. A larger study will be needed to test whether current-based defibrillation is superior to energy-based defibrillation.

Atrial defibrillation. New frontiers

External electrical atrial defibrillation was developed in the early 1960s. Direct current electrical external shocks convert atrial fibrillation to sinus rhythm in the majority of patients. Although much has been learned about the mechanisms of the arrhythmia and those responsible for successful external direct current atrial defibrillation, the technique has remained essentially unchanged since it was first described by Lown and colleagues. Animal and human studies have shown that atrial defibrillation can be terminated by shocks delivered by way of internal electrode catheters. The technique is most effective when biphasic waveform shocks are delivered by way of large surface area electrodes in the right atrium and the coronary sinus. Synchronization of shocks to R waves greater than 500 msec after the previous beat prevents induction of ventricular tachyarrhythmias. Therefore, internal atrial defibrillation provides an effective and safe method for restoring sinus rhythm in patients who fail external direct current cardioversion. The success of the implantable cardioverter-defibrillator and the encouraging safety and efficacy data from studies of internal atrial defibrillation have generated considerable interest in developing an implantable atrial defibrillator. The efficacy of low-energy shocks to terminate the arrhythmia suggests that such a device might be tolerated by patients. Data about the pathogenesis of atrial fibrillation suggest that rapid detection and immediate termination of atrial fibrillation theoretically might prevent recurrence of the arrhythmia. These data support the development of an implantable atrial defibrillator and the initiation of clinical trials to determine its utility.

Late results with concomitant coronary artery bypass grafting and ICD implantation

BACKGROUND

To determine the influence of left ventricular function on the long-term survival of patients with coronary artery disease and lethal ventricular arrhythmias, who undergo concomitant coronary artery bypass grafting (CABG) and implantable cardiovertor defibrillator (ICD) implantation, we studied survival in 54 consecutive patients who underwent CABG and ICD implantation.

METHODS

Group I consisted of 35 patients with left ventricular ejection fraction (LVEF) < or = 35% (mean 25.3 +/- 5.6) and Group II consisted of 19 patients with LVEF > 35% (mean 47.5 +/- 6.6). The two groups were similar with regards to age, gender, clinical presentation, induced arrhythmias, and the number of grafts placed at the time of surgery.

RESULTS

Two in-hospital deaths (3.7%) occurred, both in Group I. During follow-up (42.5 +/- 21.8 months), there were 10 deaths in Group I (1 noncardiac, 1 sudden, and 8 heart failure), and 1 death in Group II (heart failure) (p < 0.04).

CONCLUSIONS

Concomitant CABG and ICD implantation can be performed with an acceptable in-hospital mortality, even in patients with poor left ventricular function. Although freedom from sudden cardiac death remains excellent, overall long-term survival is limited by refractory heart failure, especially in those patients with left ventricular dysfunction at the time of surgery.

Salvage of infected ICDs: management without removal

During the 7-year period from August 1986 to December 1993, 242 patients with malignant ventricular arrhythmias underwent 242 ICD implantations and 50 subcutaneous generator changes. Wound infections developed in 5 patients (1.7%): in 3 cases, after primary implantation (3/242 [1.2%]); and in 2 following a generator change (2/50 [4.0%]). This difference was not statistically significant. Infection developed at the generator pocket and became clinically manifest between 6 weeks and 40 months, postoperatively. Our treatment approach with the first patient consisted of simple debridement of the pocket and reimplantation of the existing generator. This led to recurrence, and the generator was safely explanted. In the remaining four patients, our approach has been that of local treatment, with wide debridement of the pocket, and placement of a closed irrigation system with continuous irrigation with a bacitracin, polymyxin, neomycin solution, and culture-specific antibiotic therapy. We have successfully controlled the infection and salvaged the generator with this approach in all four patients, who are all alive and well at a mean follow-up of 25.0 +/- 17.3 months with no recurrence. The good results obtained in these patients suggest that the concept of total explanation of the infected ICD should be reassessed.

Occult T wave alternans in long QT syndrome

T wave alternans that is visually apparent on the ECG is a known risk factor for sudden death in idiopathic long QT syndrome (LQTS). To determine if occult and visually undetectable forms of T wave alternans are also present in LQTS, we measured T wave alternans from a 16-year-old girl with LQTS during exercise using spectral analysis methods and a recording system designed to minimize exercise-related noise. While there was no alternans at rest, statistically significant, yet visually inapparent T wave alternans were measured both during exercise and recovery. Using identical recording techniques, no significant T wave alternans was detected from the subject's mother, who had a prolonged QT interval but was not experiencing arrhythmias, nor from five healthy volunteers with normal QT intervals. This report suggests that electrocardiographically occult, yet prognostically important forms of T wave alternans may be present in patients with LQTS.

Classification of death in antiarrhythmia trials

OBJECTIVES

We sought to develop and apply a new scheme for the classification of death to be used in trials of antiarrhythmia treatments.

BACKGROUND

Because presently accepted classifications of death do not fully describe or tabulate all significant aspects of terminal events, nor do they consider unique aspects of arrhythmia investigations, a new classification scheme that addresses these issues is desirable.

METHODS

A classification scheme of deaths that occur in antiarrhythmia trials was developed using the following categories: 1) primary organ cause (cardiac [arrhythmic, nonarrhythmic or unknown], noncardiac or unknown); 2) temporal course (sudden, nonsudden or unknown); 3) documentation (witnessed, monitored [yes, no or unknown]); 4) operative relation (preoperative, perioperative or postoperative); and 5) system relation (procedure related, pulse generator related and lead related [yes, no or unknown]).

RESULTS

The classification scheme was used in a clinical trial of a new implantable cardioverter-defibrillator (1,250 patients, of whom 79 died) and used in an application for device market approval. Application of the classification to data reported using an older classification scheme is demonstrated.

CONCLUSIONS

We propose a descriptive classification scheme that 1) fully describes and tabulates all significant aspects of terminal events; 2) incorporates previously used categorizations of death and new categorizations that address unique aspects of arrhythmia investigations; and 3) tabulates sufficient data to allow comparison with other studies. Events in a clinical trial of implantable defibrillator therapy were classified using the new classification scheme.

Time domain analysis of the signal averaged electrocardiogram in patients with a conduction defect or a bundle branch block

Doubts have been expressed about the clinical usefulness of time domain analysis of the signal averaged electrocardiogram in patients with prolonged QRS complex duration. We studied 147 patients using a signal averaged ECG (40-250 Hz) whose QRS complex was longer than 100 ms. A baseline electrophysiology study was also performed in 128 of these patients. Seventy-seven patients had a minor (QRS < 120 and > 100 ms) conduction defect. Thirty-seven of these 77 had either induced or spontaneous sustained ventricular tachycardia (group I) and 40 had no sustained ventricular tachycardia (group II). Seventy patients had a major (QRS > or = 120 ms) conduction defect, 44 of whom had sustained ventricular tachycardia (group A). The remaining 26 without this condition formed Group B. Group I compared to group II patients had a longer filtered QRS duration (120.8 +/- 14 vs 104.5 +/- 9.5 ms, P < 0.001), a longer low amplitude signal duration (41 +/- 12.1 vs 31 +/- 12.6 ms, P < 0.0001) and a lower root mean square of the last 40 ms of the filtered QRS complex (27 +/- 29.8 vs 35 +/- 25.3 microV, P = ns). Group A compared to group B had a longer filtered QRS duration (157.7 +/- 20.2 vs 140.7 +/- 15.7 ms, P < 0.001), a longer low amplitude signal duration (57.3 +/- 24.9 vs 37.8 +/- 20.3 ms P < 0.001) and a lower root mean square of the last 40 ms of the filtered QRS complex (14.3 +/- 11.2 vs 22.0 +/- 10.5 microV, P < 0.01). Using conventional late potential criteria, the sensitivity and specificity of the signal averaged ECG for the detection of sustained ventricular tachycardia patients with a minor conduction defect were 89% and 75%, respectively. The same criteria applied to patients with a major conduction defect were sensitive (sensitivity: 87%) but non-specific (specificity: 50%). However, by using modified late potential criteria, such as the presence of two of any of the following three signal averaged parameters: filtered QRS duration > or = 145 ms, low amplitude signal duration > or = 50 ms, root mean square of the last 40 ms of the filtered QRS complex < or = 17.5 microV, we derived a non-optimal but still acceptable combination of sensitivity (68%) and specificity (73%). We conclude that traditional late potential criteria can be applied in patients with a minor conduction defect, but modification of these criteria is necessary to derive useful clinical information for risk stratification of patients with a QRS complex duration > or = 120 ms.