William B. Nelson

Continuing warfarin therapy is superior to interrupting warfarin with or without bridging anticoagulation therapy in patients undergoing pacemaker and defibrillator implantation

BACKGROUND Current guidelines recommend stopping oral anticoagulation and starting bridging anticoagulation with intravenous heparin or subcutaneous enoxaparin when implanting a pacemaker or defibrillator in patients at moderate or high risk for thromboembolic events. A limited body of literature suggests that device surgery without cessation of oral anticoagulation may be feasible. OBJECTIVE The purpose of this study was to evaluate the safety of device surgery in orally anticoagulated patients without interrupting warfarin therapy. METHODS We performed a retrospective study of 459 consecutive patients on chronic warfarin therapy who underwent device surgery from April 2004 to September 2008. Warfarin was continued in 222 patients during the perioperative period. Warfarin was temporarily held and bridging therapy administered in 123 patients. Warfarin was temporarily held without bridging therapy in 114 patients. RESULTS There were no significant differences with regard to age, sex, or risk factors for thromboembolism in the three groups. Patients who continued taking warfarin had a lower incidence of pocket hematoma (P = .004) and a shorter hospital stay (P <.0001) than did patients in the bridging group. Holding warfarin without bridging is associated with a higher incidence of transient ischemic attacks (P = .01). CONCLUSION Temporarily interrupting anticoagulation is associated with increased thromboembolic events, whereas cessation of warfarin with bridging anticoagulation is associated with a higher rate of pocket hematoma and a longer hospital stay. Continuing warfarin with a therapeutic international normalized ratio appears to be a safe and cost-effective approach when implanting a pacemaker or defibrillator in patients with moderate to high thromboembolic risk.

Predictors of inotrope use in patients undergoing concomitant coronary artery bypass graft (CABG) and aortic valve replacement (AVR) surgeries at separation from cardiopulmonary bypass (CPB).

BackgroundLeft ventricular dysfunction is common after coronary artery bypass graft and valve replacement surgeries and is often treated with inotropic drugs to maintain adequate hemodynamic status. In this study, we aimed to identify the demographic, clinical, laboratory, echocardiographic and hemodynamic factors that are associated with use of inotropic drugs in patients undergoing concomitant coronary artery bypass graft and aortic valve replacement surgery.MethodsThe study included 97 patients who had undergone concomitant coronary artery bypass graft and aortic valve replacement at Regions Hospital, University of Minnesota Medical School from January 2006 to December 2008. All data were collected retrospectively after reviewing electronic medical records. Inotropic support was defined as the use of dopamine [greater than or equal to] 5 ug/kg/min; any dose of epinephrine, norepinephrine, dobutamine, and milrinone at the separation from cardiopulmonary bypass.ResultsInotropic support was used in a total of 50 patients (52%) at the separation from cardiopulmonary bypass. Average age of the patients requiring inotropic support was 72.2 +/- 8.8 years. The study identified four significant, independent predictors of inotrope use: (1) Cardiac index [less than or equal to]2.5 L/min/m2, (2) LVEDP [greater than or equal to] 20 mm Hg, (3) LVEF [less than or equal to]40%, and (4) CKD stage 3 to 5.ConclusionWe identified four independent risk factors for postoperative use of inotropic support in patients undergoing concomitant coronary artery bypass graft and arotic valve replacement surgery at the separation from cardiopulmonary bypass. The study results will be helpful to prospectively identify patients who will likely to require inotropic support at the separation from cardiopulmonary bypass.

Transient cardiac standstill induced by adenosine in the management of intraoperative aneurysmal rupture: technical case report.

OBJECTIVE AND IMPORTANCE Intraoperative aneurysmal rupture represents a potentially catastrophic event. We describe the use of an intravenous adenosine bolus to induce transient cardiac asystole to control a severe intraoperative aneurysmal rupture. This treatment resulted in a brief period of severe hypotension, which enabled successful clipping of the aneurysm. CLINICAL PRESENTATION A 55-year-old man was referred to our institution 7 days after experiencing a mild subarachnoid hemorrhage from a fusiform, multilobulated aneurysm of the anterior communicating artery. The patient was found to have multiple additional fusiform aneurysms as well as a large parietal arteriovenous malformation. INTERVENTION A craniotomy was performed to clip the aneurysm, but surgical dissection was complicated by premature rebleeding that could not be controlled satisfactorily with tamponade or temporary arterial occlusion. Infusion of adenosine resulted in the rapid onset of profound hypotension, allowing for safe completion of the dissection and clipping of the aneurysm with a good outcome. There were no complications identified in relation to the use of adenosine. CONCLUSION In the setting of severe intraoperative aneurysmal rupture, intravenous adenosine represents a potential means of achieving a near-immediate profound decrease in the blood pressure that may allow for safe completion of the dissection and aneurysm clipping.

Normalization of Left Ventricular Ejection Fraction and Incidence of Appropriate Antitachycardia Therapy in Patients With Implantable Cardioverter Defibrillator for Primary Prevention of Sudden Death

BACKGROUND Patients with severely depressed left ventricular ejection fractions (LVEFs) receive implantable cardioverter-defibrillators (ICDs) for the primary prevention of sudden death. In some patients, however, LVEF may improve or even normalize over time. Limited data are available on the incidence of appropriate antitachycardia therapy, including pacing and shock, in these patients. METHODS AND RESULTS We retrospectively identified consecutive patients at our institution with an ICD for primary prevention who had LVEF measurement available at initial implantation and at the time of generator replacement. None of these patients had ever received appropriate antitachycardia therapy before generator replacement. The incidence of appropriate antitachycardia therapy after generator replacement was assessed. Of the 125 patients who received generator replacement, 53 (42%) received an ICD and 72 (58%) a cardiac resynchronization therapy-defibrillator (CRT-D). Among them, 30 (21%) had LVEF normalized to ≥50%, 25 (17%) had LVEF partially improved to 36%-49%, and 70 (63%) had LVEF that remained depressed at ≤35%. During an overall follow-up period of 25 ± 18 months, none of the individuals with normalized LVEF experienced appropriate antitachycardia therapy regardless of ICD or CRT-D. Meanwhile, 20% of patients with LVEF at 36%-49% and 14% of patients with LVEF at ≤35% received appropriate ICD therapy. The omnibus P value for any differences among the 3 LVEF groups was 0.046 for the entire cohort, 0.01 for ICD, and 0.15 for CRT-D patients. CONCLUSIONS These preliminary data suggest that patients with reduced LVEF and primary-prevention ICDs who normalize their LVEF over time may be at lower risk of appropriate antitachycardia therapy.

Anatomic versus effective orifice area in a bicuspid aortic valve.

Bicuspid aortic valve (BAV) is the most common congenital cardiac anomaly, with an estimated 1–2% of the population being affected. Pathology associated with BAV includes increased rates of aortic stenosis, aortic insufficiency, endocarditis, aortic dissection, and aortic coarctation. Aortic stenosis is the most frequently observed clinically, as well as in the echocardiography laboratory. Aortic valve area (AVA) is an integral component for assessing aortic stenosis severity. The primary reason for this is that AVA is theoretically less affected by flow variation in comparison with velocities and pressure gradients. AVA can be calculated both by the continuity equation, which provides functional or effective orifice area (EOA), and planimetry, which provides the geometric or anatomic orifice area (AOA). An important limitation of planimetry is that the measurement must be taken at the leaflet tips, as displacement toward the ventricle can result in an overestimation of AOA. This is due to the funnel-shaped outflow associated with aortic stenosis. The evaluation of AVA in BAV can be challenging when compared to trileaflet aortic valves. A strong correlation exists between AOA and EOA in trileaflet, stenotic valves. This same relationship is much weaker in BAV, with AOA often overestimating EOA. Potential causes or contributors to this in BAV include eccentric systolic flow patterns, valve shape, and valve profile. Eccentricity results in forward flow that collides with the aortic wall, which may potentially increase resistance. Eccentric flow also results in inefficient use of the AOA, resulting in a vena contracta (the narrowest point of flow, corresponding with the EOA and peak velocity) occurring distal to the AOA. This is referred to as the contraction of flow. The ratio of the AOA and EOA is called the coefficient of contraction. A smaller coefficient of contraction, and therefore a larger difference between AOA and EOA results in higher peak and mean pressure gradients than would be expected by the AOA alone. Valve shape and valve profile also impact the coefficient of contraction. Circular orifices are associated with higher coefficients of contraction, while eccentric orifices are associated with lower coefficients of contraction. This is likely due to the greater frictional losses associated with eccentric orifices, with the end result being a greater functional stenosis severity. Funnelshaped valves, or those with a progressive decrease in cross-sectional area, are associated with larger coefficients of contraction. Valves that have a flatter surface and abruptly narrow are associated with smaller coefficients of contraction and greater functional stenosis severity. Any of these variables alone or in combination can result in a worse functional stenosis severity than would be predicted by the AOA. Pressure recovery is an important consideration in aortic stenosis and especially in those cases when the Doppler data are discordant with two-dimensional or clinical data. Pressure recovery is considered “the increase of pressure downstream from a stenosis due to reconversion of kinetic energy into potential energy.” This phenomenon is most relevant when the proximal aorta is small, and should be considered clinically when the proximal aorta is less than 3 cm in diameter. The impact of pressure recovery is reduced when the proximal aorta is large, the left ventricular outflow tract is large, and when there is eccentric systolic flow. Therefore, BAV is Address for correspondence and reprint requests: Chad House, B.S., R.D.C.S., Mail Stop 11102M, 640 Jackson Street, St. Paul, MN 55101, USA. Fax: 651-254-3526; E-mail: chad.m.house@healthpartners.com

Mitral valve area by the pressure half-time method does not correlate with mean gradient in mitral valve repair patients.

AIMS Pressure half-time is an inaccurate measure of mitral valve area in many clinical situations. The utility of the pressure half-time method to calculate mitral valve area after mitral valve repair is not well defined. METHODS AND RESULTS Forty-two patients with a repaired mitral valve were identified. Mitral valve area was calculated by both the pressure half-time method and the continuity equation. The two mitral valve areas were then directly compared and also correlated with mean gradient. The two mitral valve areas were significantly different from one another with a mean of 1.81 ± 0.53 cm(2) by continuity equation and 2.65 ± 0.69 cm(2) by pressure half-time. The continuity equation correlated well with mean gradient (ρ = -0.63), whereas the correlation for pressure half-time was weak (r = -0.08). CONCLUSION A non-linear, inverse correlation was found between mitral valve area by the continuity equation and mean gradient. No correlation was found between the pressure half-time method for mitral valve area and mean gradient. The continuity equation likely provides a better estimate of mitral valve area in repaired mitral valves.

Predictors of appropriate therapy in patients with implantable cardioverter-defibrillator for primary prevention of sudden cardiac death.

The purpose of this study was to evaluate predictors of appropriate therapy in patients with implantable cardioverter-defibrillators (ICD) for primary prevention of sudden cardiac death. A retrospective cohort of 321 patients with systolic heart failure undergoing ICD placement for primary prevention of sudden cardiac death was queried with a mean follow-up period of 2.6 years. Appropriate ICD therapy was defined as therapy delivered for termination of a ventricular tachyarrhythmia. Appropriate ICD therapy was delivered in 142 (44%) of the patients. In a multivariate model, body mass index ≥28.8 kg/m2, chronic kidney disease, left ventricular ejection fraction ≤20% and metabolic syndrome were found to be independent predictors of appropriate ICD therapy. Appropriate ICD therapy was associated with higher cardiovascular mortality. These findings show the importance of identification of risk factors, especially metabolic syndrome, in patients following ICD implantation as aggressive treatment of these co-morbidities may decrease appropriate ICD therapy and cardiovascular mortality.

Feasibility of an Elective Cardioversion Service Led by Advanced Practice Providers without Direct Cardiologist Supervision

Background: Elective direct current cardioversion (DCCV) has traditionally been performed by physicians in the United States. A few recent reports from the United Kingdom suggested that a specialist nurse-led service for elective DCCV of persistent atrial fibrillation was feasible. This practice has not been reported in the United States previously. Several years ago, we introduced a program where specially trained advanced practice providers (APPs) (physician assistants and nurse practitioners) assisted by an anesthesiology team, performed elective DCCV in patients with atrial fibrillation and atrial flutter, without direct cardiologist supervision. Methods: Upon receiving approval from the Institutional Review Board, we conducted a retrospective analysis of 447 consecutive DCCVs electively performed by APPs, for atrial fibrillation or atrial flutter, at Regions Hospital between 12/2006 and 10/2010. Transient deep sedation was administered by an anesthesiology team. The cohort was evaluated for procedural success and safety. Results: The procedural success rate was 92% (412/447). The incidence of procedural related adverse events, requiring immediate intervention, was 0.2% (1/447). This patient required emergent temporary pacing catheter insertion followed by a permanent pacemaker implantation at a later date. There were no other procedure-related complications and no thromboembolic events. A comparison with fifty elective cardioversions performed by cardiologists during the same period found no statistical difference in procedural success rates or complications. Conclusion: Under deep sedation administered by anesthesiology service, elective DCCV of atrial fibrillation and atrial flutter performed by well-trained APPs, without direct cardiologist supervision, is feasible and does not compromise patient safety.

The Association Between Cardiac Rehabilitation Attendance and Hospital Readmission

Purpose: Cardiac rehabilitation is associated with improved clinical outcomes, but the impact of individual cardiac rehabilitation sessions on readmission rates is less studied. Methods: A retrospective evaluation of the relationship between the number of cardiac rehabilitation sessions completed and all-cause and cardiac readmission rates at 1 year was conducted. The 1-year cardiac readmission counts were modeled via Poisson regression. Results: Of the 347 patients included in the primary analysis, 227 (65%) completed all assigned cardiac rehabilitation sessions. At 1 year, 135 patients (39%) had at least 1 cardiac readmission, and 155 patients (45%) had at least 1 all-cause readmission. The primary result was that every additional cardiac rehabilitation session completed was associated with a 1.75% lower incidence rate of 1-year cardiac readmission (P = .01) and a 2% lower incidence rate of all-cause hospital readmission (P = .001). Conclusion: Regardless of the number of cardiac rehabilitation sessions assigned, each additional session attended was associated with reduced cardiac readmission by 1.75% and all-cause readmission by 2%.

Reply: To PMID 24813638.

We sincerely thank Dr. Seaman and Dr. Sucosky for their interest in our recent publication, and appreciate their bringing their recent, interesting publication to our attention. Collaboration between clinicians and academicians is essential to improving insight into the complex assessment of stenosis severity in bicuspid aortic valve (BAV). As Dr. Seaman and Dr. Sucosky demonstrated, the difference between anatomic orifice area (AOA) and effective orifice area (EOA) is exacerbated in calcified aortic valves. In addition to a reduction in orifice area and a reduction in leaflet excursion, calcification is also associated with increased leaflet stiffness. This increase in leaflet stiffness could potentially decrease the “doming” that is typically seen in BAV and thus decrease the gradual taper that allows for the coefficient of contraction to remain closer to one. This increase in leaflet stiffness may occur with very little corresponding decrease in the AOA, but with a significant change in EOA. Pressure recovery was not considered a factor in our clinical case, but is a recognized cause of Doppler echocardiography underestimating Gorlin-derived EOAs. This is especially true when the proximal aorta is of small caliber (<3 cm in diameter). Dr. Seaman and Dr. Sucosky discuss the energy loss coefficient in their letter, and this equation can be applied clinically as well. Garcia et al. demonstrated that the equation: