Travel distance and outcomes after surgical aortic valve among veterans

OBJECTIVE

To investigate the association between travel distance and postoperative length of stay (LOS) and discharge disposition among veterans undergoing surgical aortic valve replacement (SAVR).

DATA SOURCES/STUDY SETTING

We performed a retrospective cohort study of patients undergoing SAVR, with or without coronary artery bypass grafting (CABG) at VA Boston Healthcare (January 1, 2005-December 31, 2015).

STUDY DESIGN

Postoperative LOS and discharge disposition were compared for SAVR patients based on travel distance to the facility: <100 miles or ≥100 miles. Multivariable regression was performed to ascertain factors associated with LOS and home discharge.

DATA COLLECTION/EXTRACTION METHODS

Data were collected via chart review. All patients undergoing SAVR at our institution who primarily resided within the defined region were included.

PRINCIPAL FINDINGS

Of 597 patients studied, 327 patients underwent isolated SAVR; 270 patients underwent SAVR/CABG. Overall median (IQR) distance between the patient's residence and the hospital was 49.95 miles (27.41-129.94 miles); 190 patients (32%) resided further than 100 miles away. There were no differences in the proportion of patients with diabetes, hypertension, chronic obstructive pulmonary disease (COPD), cerebrovascular disease, atrial fibrillation, or prior myocardial infarction between groups. Overall LOS (IQR) was 9 (7-13) days and did not differ between groups (p = 0.18). The proportion of patients discharged home was higher among patients who resided more than 100 miles from the hospital (71% vs. 58%, p = 0.01). On multivariable analysis, residing further than 100 miles from the hospital was independently associated with home discharge (OR = 1.64, 95% CI: 1.09-2.48). Travel distance was not associated with LOS.

CONCLUSIONS

Based on our institutional experience, potential concerns of longer hospital stay or discharge to other inpatient facilities for geographically distanced patients undergoing SAVR do not appear supported. Continued examination of the drivers underlying the marked shift of veterans to the private sector appears warranted.

Performance of left internal thoracic artery-left anterior descending artery anastomosis by residents versus attendings and coronary artery bypass grafting outcomes

OBJECTIVES

Performance of a technically sound left internal thoracic artery to left anterior descending artery (LITA-LAD) anastomosis during coronary artery bypass grafting (CABG) is critically important. We used prospectively collected data from the multicentre, randomized REGROUP (Randomized Endograft Vein Perspective) trial to investigate CABG outcomes based on whether a resident or an attending surgeon performed the LITA-LAD anastomosis.

METHODS

This was a post hoc subanalysis of the REGROUP trial, which randomized veterans undergoing isolated on-pump CABG to endoscopic versus open vein harvest from 2014 through 2017. The primary end point was major cardiac adverse events, defined as the composite of all-cause deaths, nonfatal myocardial infarctions or repeat revascularizations.

RESULTS

Among 1,084 patients, 344 (31.8%) LITA-LAD anastomoses were performed by residents and 740 (68.2%), by attending surgeons. Residents (compared to attendings) operated on fewer patients with high tercile SYNTAX scores (22.1% vs 37.4%, P < 0.001), performed fewer multiarterial CABGs (5.2% vs 14.6%, P < 0.001) and performed more anastomoses to distal targets with diameters > 2.0 mm (19.0% vs 10.9%, P < 0.001) and non-calcified landing zones (25.1% vs 21.6%, P < 0.001). During a median observation time of 4.7 years (interquartile range 3.84-5.45), major cardiac adverse events occurred in 77 patients (22.4%) in the group treated by residents and 169 patients (22.8%) in the group treated by attendings (unadjusted HR 1.00; 95% confidence interval, 0.76-1.33; P = 0.99). Outcomes persisted on adjusted analyses.

CONCLUSIONS

Based on this REGROUP trial subanalysis, under careful supervision and with appropriate patient selection, LITA-LAD anastomoses performed by the residents yielded clinical outcomes similar to those of the attendings.

Impact of Oral Anticoagulation on Clinical Outcomes in Postoperative Atrial Fibrillation

INTRODUCTION

The impact of postoperative oral anticoagulation (OAC) with warfarin on postoperative atrial fibrillation (POAF) after coronary artery bypass grafting (CABG) was the focus of this examination of patients from the randomized endo-vein graft prospective (REGROUP) Trial.

MATERIAL AND METHODS

REGROUP was a prospective randomized Veterans Affairs cooperative study comparing endoscopic versus open vein harvest in elective CABG patients (March 2014-April 2017) at 16 Veterans Affairs facilities. This study compared new-onset POAF patients who were treated with warfarin versus no-warfarin. Outcomes included stroke during active follow-up and a major adverse cardiac event composite of mortality, acute myocardial infarction, and repeat revascularization during active and passive follow-up.

RESULTS

Of the 316/1103 (28.6%) of REGROUP patients who developed new-onset POAF, 45 patients were excluded - mainly for preoperative warfarin use. Of the remaining 269 patients, 85 received OAC with warfarin (OAC group); 184 did not (no-OAC group). Stroke rates during active follow-up (32 [IQR 24-38] mo) were 3.5% OAC group versus 5.4% no-OAC group (P = 0.76); major adverse cardiac eventrates were 20% OAC versus 11.4% no-OAC (P = 0.06). On longer follow-up of (median 4.61 [IQR 3.9-5.1] y), discharge OAC use was associated with all-cause mortality after adjusting for Society of Thoracic Surgeons mortality risk (20.0% versus 11.4% no-OAC use; HR = 2.00, 95% CI: 1.05-3.81, P = 0.035).

CONCLUSIONS

REGROUP patients with POAF treated with OAC had similar stroke and higher mortality rates versus no-OAC patients. Further investigation of the risk-benefit ratio of OAC in post-CABG patients and which POAF patient subgroups might derive the most benefit with anticoagulation appears warranted.

Postoperative Atrial Fibrillation After Surgical Aortic Valve Replacement: Amiodarone and Warfarin Use

INTRODUCTION

The association between amiodarone treatment for postoperative atrial fibrillation (POAF) after surgical aortic valve replacement (SAVR) and both the return to normal sinus rhythm (NSR) and anticoagulation use at discharge has not been extensively studied.

METHODS

We retrospectively identified all patients who underwent biological SAVR with or without concomitant coronary artery bypass grafting (CABG) at a Veterans Affairs Medical Center (2005-2015). We reviewed new-onset POAF, amiodarone use, return to NSR, and anticoagulation use with warfarin. Discharge rhythm and warfarin administration were compared among patients with POAF who were treated with amiodarone and patients who did not receive amiodarone.

RESULTS

Of the 395 patients (186 AVR/coronary artery bypass grafting; 209 AVR) studied, POAF developed in 191 patients (48.0%); 80.1% (153/191) of these patients received amiodarone. Among patients treated with amiodarone, 70.6% (108/153) were in SR at the time of discharge versus 65.8% (25/38) of POAF patients who were not treated with amiodarone (P = 0.57). Among amiodarone-treated patients, 30.7% (47/153) were discharged with warfarin; among patients not treated with amiodarone, 31.6% (12/38) were discharged with warfarin (P = 0.92). Among amiodarone-treated patients discharged in NSR, 89.9% (97/108 patients) were not discharged with warfarin; among patients not treated with amiodarone who were discharged in NSR, 92% (23/25) were not discharged with warfarin (P = 0.74).

CONCLUSIONS

POAF after SAVR appears common. Although amiodarone is often used for POAF patients, its use does not appear to be associated with surgeons' decision to anticoagulate patients. Surgeons' preferences for using rhythm control and antithrombotic therapy for POAF after SAVR warrant further exploration.

Health-related quality of life impacts upon 5-year survival after coronary artery bypass surgery

BACKGROUND

Poor preoperative health-related quality of life (HRQoL) has been associated with reduced short-term survival after coronary artery bypass graft (CABG) surgery; however, its impact on long-term mortality is unknown. This study's objective was to determine if baseline HRQoL status predicts 5-year post-CABG mortality.

METHODS

This prespecified, randomized on/off bypass follow-up study (ROOBY-FS) subanalysis compared baseline patient characteristics and HRQoL scores, obtained from the Seattle Angina Questionnaire (SAQ) and Veterans RAND Short Form-36 (VR-36), between 5-year post-CABG survivors and nonsurvivors. Standardized subscores were calculated for each questionnaire. Multivariable logistic regression assessed whether HRQoL survey subcomponents independently predicted 5-year mortality (p ≤ .05).

RESULTS

Of the 2203 ROOBY-FS enrollees, 2104 (95.5%) completed baseline surveys. Significant differences between 5-year post-CABG deaths (n = 286) and survivors (n = 1818) included age, history of chronic obstructive pulmonary disease, stroke, peripheral vascular disease, renal dysfunction, diabetes, lower left ventricular ejection fraction, atrial fibrillation, depression, non-White race/ethnicity, lower education status, and off-pump CABG. Adjusting for these factors, baseline VR-36 physical component summary score (p = .01), VR-36 mental component summary score (p < .001), and SAQ physical limitation score (p = .003) were all associated with 5-year all-cause mortality.

CONCLUSIONS

Pre-CABG HRQoL scores may provide clinically relevant prognostic information beyond traditional risk models and prove useful for patient-provider shared decision-making and enhancing pre-CABG informed consent.

Ten-Year Outcomes of Off-Pump vs On-Pump Coronary Artery Bypass Grafting in the Department of Veterans Affairs: A Randomized Clinical Trial

IMPORTANCE

The long-term benefits of off-pump ("beating heart") vs on-pump coronary artery bypass grafting (CABG) remain controversial.

OBJECTIVE

To evaluate the 10-year outcomes and costs of off-pump vs on-pump CABG in the Department of Veterans Affairs (VA) Randomized On/Off Bypass (ROOBY) trial.

DESIGN, SETTING, AND PARTICIPANTS

From February 27, 2002, to May 7, 2007, 2203 veterans in the ROOBY trial were randomly assigned to off-pump or on-pump CABG procedures at 18 participating VA medical centers. Per protocol, the veterans were observed for 10 years; the 10-year, post-CABG clinical outcomes and costs were assessed via centralized abstraction of electronic medical records combined with merges to VA and non-VA databases. With the use of an intention-to-treat approach, analyses were performed from May 7, 2017, to December 9, 2021.

INTERVENTIONS

On-pump and off-pump CABG procedures.

MAIN OUTCOMES AND MEASURES

The 10-year coprimary end points included all-cause death and a composite end point identifying patients who had died or had undergone subsequent revascularization (ie, percutaneous coronary intervention [PCI] or repeated CABG); these 2 end points were measured dichotomously and as time-to-event variables (ie, time to death and time to composite end points). Secondary 10-year end points included PCIs, repeated CABG procedures, changes in cardiac symptoms, and 2018-adjusted VA estimated costs. Changes from baseline to 10 years in post-CABG, clinically relevant cardiac symptoms were evaluated for New York Heart Association functional class, Canadian Cardiovascular Society angina class, and atrial fibrillation. Outcome differences were adjudicated by an end points committee. Given that pre-CABG risks were balanced, the protocol-driven primary and secondary hypotheses directly compared 10-year treatment-related effects.

RESULTS

A total of 1104 patients (1097 men [99.4%]; mean [SD] age, 63.0 [8.5] years) were enrolled in the off-pump group, and 1099 patients (1092 men [99.5%]; mean [SD] age, 62.5 [8.5] years) were enrolled in the on-pump group. The 10-year death rates were 34.2% (n = 378) for the off-pump group and 31.1% (n = 342) for the on-pump group (relative risk, 1.05; 95% CI, 0.99-1.11; P = .12). The median time to composite end point for the off-pump group (4.6 years; IQR, 1.4-7.5 years) was approximately 4.3 months shorter than that for the on-pump group (5.0 years; IQR, 1.8-7.9 years; P = .03). No significant 10-year treatment-related differences were documented for any other primary or secondary end points. After the removal of conversions, sensitivity analyses reconfirmed these findings.

CONCLUSIONS AND RELEVANCE

No off-pump CABG advantages were found for 10-year death or revascularization end points; the time to composite end point was lower in the off-pump group than in the on-pump group. For veterans, in the absence of on-pump contraindications, a case cannot be made for supplanting the traditional on-pump CABG technique with an off-pump approach.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01924442.

Analysis of Dynamic Changes in Cognitive Workload During Cardiac Surgery Perfusionists' Interactions With the Cardiopulmonary Bypass Pump

OBJECTIVE

This novel preliminary study sought to capture dynamic changes in heart rate variability (HRV) as a proxy for cognitive workload among perfusionists while operating the cardiopulmonary bypass (CPB) pump during real-life cardiac surgery.

BACKGROUND

Estimations of operators' cognitive workload states in naturalistic settings have been derived using noninvasive psychophysiological measures. Effective CPB pump operation by perfusionists is critical in maintaining the patient's homeostasis during open-heart surgery. Investigation into dynamic cognitive workload fluctuations, and their relationship with performance, is lacking in the literature.

METHOD

HRV and self-reported cognitive workload were collected from three Board-certified cardiac perfusionists (N = 23 cases). Five HRV components were analyzed in consecutive nonoverlapping 1-min windows from skin incision through sternal closure. Cases were annotated according to predetermined phases: prebypass, three phases during bypass, and postbypass. Values from all 1min time windows within each phase were averaged.

RESULTS

Cognitive workload was at its highest during the time between initiating bypass and clamping the aorta (preclamp phase during bypass), and decreased over the course of the bypass period.

CONCLUSION

We identified dynamic, temporal fluctuations in HRV among perfusionists during cardiac surgery corresponding to subjective reports of cognitive workload. Not only does cognitive workload differ for perfusionists during bypass compared with pre- and postbypass phases, but differences in HRV were also detected within the three bypass phases.

APPLICATION

These preliminary findings suggest the preclamp phase of CPB pump interaction corresponds to higher cognitive workload, which may point to an area warranting further exploration using passive measurement.

Coronary Artery Bypass Grafting Transit Time Flow Measurement: Graft Patency and Clinical Outcomes

BACKGROUND

This subanalysis of the Randomized On-Off Bypass (ROOBY) trial examined transit time flow measurement (TTFM) use and its impact on graft patency and long-term clinical outcomes after coronary artery bypass graft surgery.

METHODS

Use of TTFM for ROOBY centers and surgeons was assessed. Comparative patient outcomes based on TTFM use included 1-year graft patency and 1-year and 5-year major adverse cardiac events: all-cause mortality, nonfatal myocardial infarction, and revascularization (percutaneous coronary intervention or repeat coronary artery bypass graft surgery).

RESULTS

Transit time flow measurement was used in 1067 patients (TTFM group) and not used in 501 patients (non-TTFM group); of the TTFM group, median percentage TTFM use was 79% (interquartile range, 41% to 98%) among 18 Veterans Affairs Medical Centers, and 74% (interquartile range, 13% to 98%) among 48 surgeons. Patients were comparable in age (63 ± 8.5 years TTFM vs 62 ± 8 years non-TTFM, P = .30) and estimated 30-day mortality risk (1.8 ± 1.7 TTFM vs 1.9 non-TTFM, P = .53). One-year FitzGibbon A patency was 83% (1600 of 1988 grafts) for TTFM assessed grafts and 78% (629 of 803) for non-TTFM assessed grafts (P < .01). Fewer TTFM patients had an occluded graft (29%, vs 38% non-TTFM; P = .01). Comparing TTFM patients with non-TTFM patients, 5-year major adverse cardiac event rates were 30% vs 25% (P = .06). Individual component rates were 14% vs 11% for death (P = .06), 12% vs 8.8% for myocardial infarction (P = .07), and 13% vs 12% for revascularization (P = .62).

CONCLUSIONS

The association of TTFM use with graft patency and clinical outcome is uncertain. Future randomized studies that account for patient risk factors and practice variation would help address this knowledge gap.

Incidence and Prognostic Impact of Incomplete Revascularization Documented by Coronary Angiography 1 Year After Coronary Artery Bypass Grafting

Complete revascularization (CR) at the time of coronary artery bypass graft (CABG) surgery improves long-term cardiac outcomes. No studies have previously reported angiographically confirmed CR rates post-CABG. This study's aim was to assess the impact upon long-term outcomes of CR versus incomplete revascularization (IR), confirmed by coronary angiography 1 year after CABG. Randomized On/Off Bypass Study patients who returned for protocol-specified 1-year post-CABG coronary angiograms were included. Patients with a widely patent graft supplying the major diseased artery within each diseased coronary territory were considered to have CR. Outcomes were all-cause mortality and major adverse cardiovascular events (MACE; all-cause mortality, nonfatal myocardial infarction, repeat revascularization) over the 4 years after angiography. Of the 1,276 patients, 756 (59%) had CR and 520 (41%) had IR. MACE was 13% CR versus 26% IR, p <0.001. This difference was driven by fewer repeat revascularizations (5% CR vs 18% IR; p <0.001). There were no differences in mortality (7.1% CR vs 8.1% IR, p = 0.13) or myocardial infarction (4% in both). Adjusted multivariable models confirmed CR was associated with reduced MACE (odds ratio 0.44, 95% confidence interval 0.33 to 0.58, p <0.01), but had no impact on mortality. In conclusion, CR confirmed by post-CABG angiography was associated with improved MACE but not mortality. Repeat revascularization of patients with IR, driven by knowledge of the research angiography results, may have ameliorated potential mortality differences.

New-onset postoperative atrial fibrillation impact on 5-year clinical outcomes and costs

OBJECTIVE

The impact of new-onset postoperative atrial fibrillation (POAF) following coronary artery bypass grafting (CABG) surgery on long-term clinical outcomes and costs is not known. This subanalysis of the Veterans Affairs "Randomized On/Off Bypass Follow-up Study" compared 5-year outcomes and costs between patients with and without POAF.

METHODS

Of the 2203 veterans in the study, 100 with pre-CABG atrial fibrillation (93) or missing data (7) were excluded (4.8%). Unadjusted and risk-adjusted outcomes were compared between new-onset POAF (n = 551) and patients without POAF (n = 1552). Five-year clinical outcomes included mortality, major adverse cardiovascular events (MACE, comprising mortality, repeat revascularization, and myocardial infarction), MACE subcomponents, stroke, and costs. A stringent P value of ≤.01 was required to identify statistical significance.

RESULTS

Patients with POAF were older and had more complex comorbidities. Unadjusted 5-year all-cause mortality was 16.3% POAF versus 11.9% no-POAF, P = .008. Unadjusted cardiac-mortality was 7.4% versus 4.8%, P = .022. There were no differences between groups in any other unadjusted outcomes including MACE or stroke. After risk adjustment, there were no significant differences between groups in 5-year all-cause mortality (POAF odds ratio, 1.19; 99% confidence interval, 0.81-1.75) or cardiac mortality (odds ratio, 1.51, 99% confidence interval, 0.88-2.60). Adjusted first-year post-CABG costs were $15,300 greater for patients with POAF, but 2- through 5-year costs were similar.

CONCLUSIONS

No 5-year risk-adjusted outcome differences were found between patients with and without POAF after CABG. Although first-year costs were greater in patients with POAF, this difference did not persist in subsequent years.

Epiaortic Ultrasound for Assessment of Intraluminal Atheroma; Insights from the REGROUP Trial

OBJECTIVES

To assess the use of epiaortic ultrasound in contemporary cardiac surgery, as well as its impact on surgical cannulation strategy and cerebrovascular events.

DESIGN

Epiaortic ultrasound data was prospectively collected in the Randomized Endovein Graft Prospective (REGROUP) trial (VA Cooperative Studies Program #588, ClinicalTrials.gov, NCT01850082), which randomized 1,150 coronary artery bypass graft patients between 2014 and 2017 to endoscopic or open-vein graft harvest.

SETTING

Sixteen cardiac surgery programs within the Veterans Affairs Healthcare System with expertise at performing endoscopic vein-graft harvesting.

PARTICIPANTS

Veterans Affairs patients, greater than 18 years of age, undergoing elective or urgent coronary artery bypass grafting with cardiopulmonary bypass and cardioplegic arrest with at least one planned saphenous vein graft were eligible for enrollment.

INTERVENTIONS

Epiaortic ultrasound was performed by the surgeon using a high frequency (>7 MHz) ultrasound transducer. Two-dimensional images of the ascending aorta in multiple planes were acquired before aortic cannulation and cross-clamping.

MEASUREMENTS AND MAIN RESULTS

Epiaortic ultrasound was performed in 34.1% (269 of 790) of patients in REGROUP. Among these patients, simple intraluminal atheroma was observed in 21.9% (59 269), and complex intraluminal atheroma comprised 2.2% (6 of 269). The aortic cannulation or cross-clamp strategy was modified based on these findings in 7.1% of cases (19 of 269). There was no difference in stroke between patients who underwent epiaortic ultrasound and those who did not (1.9% v 1.2% p = 0.523).

CONCLUSIONS

Despite current guidelines recommending routine use of epiaortic ultrasound (IIa/B) to reduce the risk of stroke in cardiac surgery, in this contemporary trial, use remains infrequent, with significant site-to-site variability.

Association Between Antithrombotic Medication Use After Bioprosthetic Aortic Valve Replacement and Outcomes in the Veterans Health Administration System

Importance

The recommendations about antithrombotic medication use after bioprosthetic aortic valve replacement (bAVR) vary.

Objectives

To describe the post-bAVR antithrombotic medication practice across the Veterans Health Administration (VHA) and to assess the association between antithrombotic strategies and post-bAVR outcomes.

Design, Setting, and Participants

Retrospective cohort study. Multivariable modeling with propensity scores was conducted to adjust for differences in patient characteristics across the 3 most common antithrombotic medication strategies (aspirin plus warfarin sodium, aspirin only, and dual antiplatelets). Text mining of notes was used to identify the patients with bAVR (fiscal years 2005-2015).

Main Outcomes and Measures

This study used VHA and non-VHA outpatient pharmacy data and text notes to classify the following antithrombotic medications prescribed within 1 week after discharge from the bAVR hospitalization: aspirin plus warfarin, aspirin only, dual antiplatelets, no antithrombotics, other only, and warfarin only. The 90-day outcomes included all-cause mortality, thromboembolism risk, and bleeding events. Outcomes were identified using primary diagnosis codes from emergency department visits or hospital admissions.

Results

The cohort included 9060 veterans with bAVR at 47 facilities (mean [SD] age, 69.3 [8.8] years; 98.6% male). The number of bAVR procedures per year increased from 610 in fiscal year 2005 to 1072 in fiscal year 2015. The most commonly prescribed antithrombotic strategy was aspirin only (4240 [46.8%]), followed by aspirin plus warfarin (1638 [18.1%]), no antithrombotics (1451 [16.0%]), dual antiplatelets (1010 [11.1%]), warfarin only (439 [4.8%]), and other only (282 [3.1%]). Facility variation in antithrombotic prescription patterns was observed. During the 90-day post-bAVR period, adverse events were uncommon, including all-cause mortality in 127 (1.4%), thromboembolism risk in 142 (1.6%), and bleeding events in 149 (1.6%). No differences in 90-day mortality or thromboembolism were identified across the 3 antithrombotic medication groups in either the unadjusted or adjusted models. Patients receiving the combination of aspirin plus warfarin had higher odds of bleeding than patients receiving aspirin only in the unadjusted analysis (odds ratio, 2.58; 95% CI, 1.71-3.89) and after full risk adjustment (adjusted odds ratio, 1.92; 95% CI, 1.17-3.14).

Conclusions and Relevance

These data demonstrate that bAVR procedures are increasingly being performed in VHA facilities and that aspirin only was the most commonly used antithrombotic medication strategy after bAVR. The risk-adjusted results suggest that the combination of aspirin plus warfarin does not improve either all-cause mortality or thromboembolism risk but increases the risk of bleeding events compared with aspirin only.

Randomized Trial of Endoscopic or Open Vein-Graft Harvesting for Coronary-Artery Bypass

BACKGROUND

The saphenous-vein graft is the most common conduit for coronary-artery bypass grafting (CABG). The influence of the vein-graft harvesting technique on long-term clinical outcomes has not been well characterized.

METHODS

We randomly assigned patients undergoing CABG at 16 Veterans Affairs cardiac surgery centers to either open or endoscopic vein-graft harvesting. The primary outcome was a composite of major adverse cardiac events, including death from any cause, nonfatal myocardial infarction, and repeat revascularization. Leg-wound complications were also evaluated.

RESULTS

A total of 1150 patients underwent randomization. Over a median follow-up of 2.78 years, the primary outcome occurred in 89 patients (15.5%) in the open-harvest group and 80 patients (13.9%) in the endoscopic-harvest group (hazard ratio, 1.12; 95% confidence interval [CI], 0.83 to 1.51; P=0.47). A total of 46 patients (8.0%) in the open-harvest group and 37 patients (6.4%) in the endoscopic-harvest group died (hazard ratio, 1.25; 95% CI, 0.81 to 1.92); myocardial infarctions occurred in 34 patients (5.9%) in the open-harvest group and 27 patients (4.7%) in the endoscopic-harvest group (hazard ratio, 1.27; 95% CI, 0.77 to 2.11), and revascularization occurred in 35 patients (6.1%) in the open-harvest group and 31 patients (5.4%) in the endoscopic-harvest group (hazard ratio, 1.14; 95% CI, 0.70 to 1.85). Leg-wound infections occurred in 18 patients (3.1%) in the open-harvest group and in 8 patients (1.4%) in the endoscopic-harvest group (relative risk, 2.26; 95% CI, 0.99 to 5.15).

CONCLUSIONS

Among patients undergoing CABG, we did not find a significant difference between open vein-graft harvesting and endoscopic vein-graft harvesting in the risk of major adverse cardiac events. (Funded by the Cooperative Studies Program, Office of Research and Development, Department of Veterans Affairs; REGROUP ClinicalTrials.gov number, NCT01850082 .).

Antithrombotic Strategies After Bioprosthetic Aortic Valve Replacement: A Systematic Review

BACKGROUND

The optimal antithrombotic regimen after bioprosthetic aortic valve replacement (bAVR) is unclear. We conducted a systematic review of various anticoagulation strategies following surgical or transcatheter bAVR (TAVR).

METHODS

We searched Medline, PubMed, Embase, Evidence-Based Medicine Reviews, and gray literature through June 2017 for controlled clinical trials and cohort studies that directly compared different antithrombotic strategies in nonpregnant adults who had undergone bAVR. We assessed risk of bias and graded the strength of the evidence using established methods.

RESULTS

Of 4,554 titles reviewed, 6 clinical trials and 13 cohort studies met inclusion criteria. We found moderate-strength evidence that mortality, thromboembolic events, and bleeding rates are similar between aspirin and warfarin after surgical bAVR. Observational data suggest lower mortality and thromboembolic events with aspirin combined with warfarin compared with aspirin alone after surgical bAVR, but the effect size is small and the combination is associated with a substantial increase in bleeding risk. We found insufficient evidence for all other treatment comparisons in surgical bAVR. In TAVR patients, we found moderate-strength evidence that mortality, stroke, and major cardiac events are similar between dual antiplatelet therapy and aspirin alone, though a nonsignificantly lower rate of bleeding occurred with aspirin alone.

CONCLUSIONS

Treatment with warfarin or aspirin leads to similar outcomes after surgical bAVR. Combining aspirin with warfarin may lead to a small decrease in thromboembolism and mortality, but is accompanied by increased bleeding. For TAVR patients, aspirin is equivalent to dual antiplatelet therapy for reducing thromboembolism and mortality, with a possible decrease in bleeding.

Off-Pump Versus On-Pump Impact: Diabetic Patient 5-Year Coronary Artery Bypass Clinical Outcomes

BACKGROUND

For diabetic patients who require coronary artery bypass graft (CABG) operation, controversy persists whether an off-pump or an on-pump approach may be advantageous. This US-based, multicenter, randomized, controlled trial, Department of Veterans Affairs Randomization On versus Off Bypass Follow-up Study, compared diabetic patients' 5-year clinical outcomes for off-pump versus on-pump procedures.

METHODS

From 2002 to 2008, 835 medically treated (ie, oral hypoglycemic agent or insulin) diabetic patients underwent either off-pump (n = 402) or on-pump (n = 433) CABG. Five-year primary end points included all-cause death and major adverse cardiovascular events (MACE; composite included all-cause death, myocardial infarction, or repeat revascularization). Secondary 5-year end points included cardiac death and MACE-related components. With baseline risk factors balanced, outcomes were evaluated by using a p value less than or equal to 0.01; nonsignificant trends were reported for p values greater than 0.01 and less than or equal to 0.15.

RESULTS

Five-year all-cause death rates were 20.2% off pump versus 14.1% on pump (p = 0.0198). No differences were seen in MACE (32.6% off-pump approach versus 28.6% on-pump approach, p = 0.216), repeat revascularization (12.4% off-pump approach versus 11.8% on-pump approach, p = 0.770), and nonfatal myocardial infarction (12.7% off-pump approach versus 10.4% on-pump approach, p = 0.299). Cardiac death trended worse with off-pump CABG (9.0%) than with on-pump CABG (6.25%, p = 0.137). Sensitivity analyses that removed conversions confirmed these findings.

CONCLUSIONS

With a 6.1% absolute difference, a strong trend toward improved 5-year survival was observed with on-pump CABG for medically treated diabetic patients. No off-pump advantage was found for any 5-year end points. A future clinical trial now appears warranted to rigorously compare off-pump versus on-pump longer term outcomes for diabetic patients.

Costs Five Years After Off-Pump or On-Pump Coronary Artery Bypass Surgery

BACKGROUND

Coronary artery bypass grafting (CABG) is a common surgical treatment for ischemic heart disease. Little is known about the long-term costs of conducting the surgery on-pump or off-pump.

METHODS

As part of the Randomized On/Off Bypass follow-up study, we followed 2,203 participants randomized to on-pump (n = 1,099) and off-pump (n = 1,104) CABG for 5 years using Department of Veterans Affairs and Medicare administrative data. We examined annual costs through 5 years, standardized to 2016 dollars, using multivariate regression models, controlling for site and baseline patient factors.

RESULTS

In the first year, including the CABG surgery, annual average costs were $66,599 (SE, $1,946) for the on-pump group and $70,552 (SE, $1,954) for the off-pump group. In years 2 to 5, average costs ranged from $15,000 to $20,000 per year. There was no significant difference between on-pump and off-pump across the 5 years. We explored differences among high-risk subgroups (diabetes, chronic obstructive pulmonary disease, peripheral vascular disease, cerebrovascular disease, renal dysfunction, ejection fraction < 35%, over age 70 years), and found no treatment assignment by time interactions, except for a nonsignificant trend in patients with diabetes.

CONCLUSIONS

At 5 years, the average costs of off-pump and on-pump CABG patients did not statistically differ. Costs do not favor one approach and the decision should be based on clinical risks, especially in subgroups. Future research is warranted to examine post-CABG costs and outcomes for diabetic patients over time.

Comparison of Outcomes and Costs Associated With Aspirin ± Clopidogrel After Coronary Artery Bypass Grafting

Optimal antiplatelet therapy after coronary artery bypass graft (CABG) surgery remains controversial. This study evaluated the role of dual antiplatelet therapy using aspirin and clopidogrel (DAPT) versus antiplatelet therapy using aspirin only (ASA) on post-CABG clinical outcomes and costs. In the Department of Veterans Affairs Randomized On/Off Bypass (ROOBY) trial, clopidogrel use after CABG was prospectively collected beginning in year 2 of this study to include 1,525 of the 2,203 original ROOBY patients who received aspirin after CABG. Discretionarily, surgeons after CABG administered either DAPT or ASA treatments. The ROOBY trial's primary 30-day composite (mortality or perioperative morbidity), 1-year composite (all-cause death, repeat revascularization, or nonfatal myocardial infarction), and costs were compared for these 2 strategies. Of the 1,525 subjects, 511 received DAPT and 1,014 received ASA. DAPT subjects, compared with ASA subjects, had lower rates of preoperative left ventricular ejection fraction of ≥45% (78.8% vs 85.7%, p <0.001), on-pump CABG (36.6% vs 57.1%, p = 0.001), and endoscopic vein harvesting (30.0% vs 42.8%, p <0.001). ASA patients were more likely to have earlier aspirin administration and receive 325 versus 81 mg dosages. The 30-day composite outcome rate was significantly lower for DAPT patients compared with ASA patients (3.3% vs 7.1%, p = 0.003), but the 1-year composite outcome was equal between the 2 groups (12.0% vs12.0%, p = 1.0). At 1 year, there were no cost differences between the 2 groups. Propensity analyses did not significantly alter the results. In conclusion, DAPT appeared safe and was associated with fewer 30-day adverse outcomes than aspirin only and with no 1-year outcome or cost differences.

Concordance between administrative data and clinical review for mortality in the randomized on/off bypass follow-up study (ROOBY-FS)

BACKGROUND

The optimal methodology to identify cardiac versus non-cardiac cause of death following cardiac surgery has not been determined.

METHODS

The Randomized On/Off Bypass Trial was a multicenter, randomized, controlled clinical trial of 2203 patients (February 2002-May 2008) comparing 1-year cardiac outcomes between off-pump and on-pump bypass surgery. In 2013, the Veterans Affairs (VA) Cooperative Studies Program funded a follow-up study to assess 5-year outcomes including mortality. Deaths were identified and confirmed using the National Death Index (NDI), VA Vital Status file, and medical records. An Endpoints Committee (EC) reviewed patient medical records and classified each cause of death as cardiac, non-cardiac, or unknown. Using pre-determined ICD-10 codes, NDI death certificates were independently used to classify deaths as cardiac or non-cardiac. Cause of death was compared between the NDI and EC classifications and concordance measured, using Kappa statistics.

RESULTS

Of the 297 5-year deaths identified by the NDI and/or VA vital status file and confirmed by the EC, 219 had adequate patient records for EC cause of death determination. The EC adjudicated 141 of these deaths as non-cardiac and 78 as cardiac, while the NDI classified 150 as non-cardiac and 69 as cardiac; agreement was 77.6% (kappa 0.500; P < 0.001).

CONCLUSIONS

Since concordance between EC and NDI cause of death classifications was only moderate, caution should be exercised in relying exclusively on NDI data to determine cause of death. A hybrid approach, integrating multiple information sources, may provide the most accurate approach to classifying cause of death.

Five-Year Outcomes after On-Pump and Off-Pump Coronary-Artery Bypass

BACKGROUND

Coronary-artery bypass grafting (CABG) surgery may be performed either with cardiopulmonary bypass (on pump) or without cardiopulmonary bypass (off pump). We report the 5-year clinical outcomes in patients who had been included in the Veterans Affairs trial of on-pump versus off-pump CABG.

METHODS

From February 2002 through June 2007, we randomly assigned 2203 patients at 18 medical centers to undergo either on-pump or off-pump CABG, with 1-year assessments completed by May 2008. The two primary 5-year outcomes were death from any cause and a composite outcome of major adverse cardiovascular events, defined as death from any cause, repeat revascularization (CABG or percutaneous coronary intervention), or nonfatal myocardial infarction. Secondary 5-year outcomes included death from cardiac causes, repeat revascularization, and nonfatal myocardial infarction. Primary outcomes were assessed at a P value of 0.05 or less, and secondary outcomes at a P value of 0.01 or less.

RESULTS

The rate of death at 5 years was 15.2% in the off-pump group versus 11.9% in the on-pump group (relative risk, 1.28; 95% confidence interval [CI], 1.03 to 1.58; P=0.02). The rate of major adverse cardiovascular events at 5 years was 31.0% in the off-pump group versus 27.1% in the on-pump group (relative risk, 1.14; 95% CI, 1.00 to 1.30; P=0.046). For the 5-year secondary outcomes, no significant differences were observed: for nonfatal myocardial infarction, the rate was 12.1% in the off-pump group and 9.6% in the on-pump group (P=0.05); for death from cardiac causes, the rate was 6.3% and 5.3%, respectively (P=0.29); for repeat revascularization, the rate was 13.1% and 11.9%, respectively (P=0.39); and for repeat CABG, the rate was 1.4% and 0.5%, respectively (P=0.02).

CONCLUSIONS

In this randomized trial, off-pump CABG led to lower rates of 5-year survival and event-free survival than on-pump CABG. (Funded by the Department of Veterans Affairs Office of Research and Development Cooperative Studies Program and others; ROOBY-FS ClinicalTrials.gov number, NCT01924442 .).

Postoperative atrial fibrillation impacts on costs and one-year clinical outcomes: the Veterans Affairs Randomized On/Off Bypass Trial

BACKGROUND

New-onset postoperative atrial fibrillation (POAF) after coronary artery bypass graft surgery (CABG) is associated with worse in-hospital morbidity and mortality, extended hospital stays, and higher costs. Beyond the initial hospital discharge, the cost and outcomes of POAF have not been well studied.

METHODS

For CABG patients with and without new-onset POAF, a retrospective propensity-matched, multivariable regression analysis was performed to compare 1-year outcomes (including health-related quality of life [HRQoL] scores and mortality rates) and costs (standardized to 2010 dollars). Regression models controlled for site and patient factors, with propensity matching used to adjust for differences in POAF versus no-POAF patients' risk profiles.

RESULTS

Using the existing CABG trial database, 2,096 patient records were analyzed, including POAF patients (n = 549) versus no-POAF patients (n = 1,547). For the index CABG hospitalization, POAF patients had longer postoperative length of stay (+3.9 days) and higher discharge costs (+$13,993) than no-POAF patients. At 1 year, POAF patients had more than twice the adjusted odds of dying (p < 0.01), with higher 1-year total cumulative costs. This 1-year cost difference (+$15,593) was largely attributable to hospital-based costs during the index surgery hospitalization. There was no difference in 1-year HRQoL scores (or HRQoL score changes) between POAF patients and no-POAF patients.

CONCLUSIONS

Compared with no-POAF patients, POAF patients had higher discharge and 1-year costs along with higher 1-year mortality rates, but no differences were observed in 1-year HRQoL scores. Additional research appears warranted to improve the longer-term survival rates for POAF CABG patients, targeting future POAF-specific postdischarge interventions.

Choice of vein-harvest technique for coronary artery bypass grafting: rationale and design of the REGROUP trial

The Randomized Endo-vein Graft Prospective (REGROUP) trial (ClinicalTrials.gov NCT01850082) is a randomized, intent-to-treat, 2-arm, parallel-design, multicenter study funded by the Cooperative Studies Program (CSP No. 588) of the US Department of Veterans Affairs. Cardiac surgeons at 16 Veterans Affairs (VA) medical centers with technical expertise in performing both endoscopic vein harvesting (EVH) and open vein harvesting (OVH) were recruited as the REGROUP surgeon participants. Subjects requiring elective or urgent coronary artery bypass grafting using cardiopulmonary bypass with use of ≥1 saphenous vein graft will be screened for enrollment using pre-established inclusion/exclusion criteria. Enrolled subjects (planned N = 1150) will be randomized to 1 of the 2 arms (EVH or OVH) after an experienced vein harvester has been assigned. The primary outcomes measure is the rate of major adverse cardiac events (MACE), including death, myocardial infarction, or revascularization. Subject assessments will be performed at multiple times, including at baseline, intraoperatively, postoperatively, and at discharge (or 30 days after surgery, if still hospitalized). Assessment of leg-wound complications will be completed at 6 weeks after surgery. Telephone follow-ups will occur at 3-month intervals after surgery until the participating sites are decommissioned after the trial's completion (approximately 4.5 years after the full study startup). To assess long-term outcomes, centralized follow-up of MACE for 2 additional years will be centrally performed using VA and non-VA clinical and administrative databases. The primary MACE outcome will be compared between the 2 arms, EVH and OVH, at the end of the trial duration.

The efficacy of supplemental magnesium in reducing atrial fibrillation after coronary artery bypass grafting

BACKGROUND

Atrial fibrillation after coronary artery bypass is reported from 17% to 53%. Hypomagnesemia after this surgery is considered a contributing factor.

METHODS

Two hundred-two coronary bypass patients were randomized to magnesium (n = 105) or placebo (n = 97). The experimental group received 80-mg magnesium sulfate per kilogram ideal weight in 100 mL dextrose 5% water 30 minutes preoperatively. Postoperatively, patients received 8-mg magnesium sulfate per kilogram ideal weight intravenous per hour more than 48 hours. The control group received dextrose 5% water at these intervals.

RESULTS

After the first bolus serum magnesium was experimental 4.75 mg/dL versus control 1.91 mg/dL, p less than 0.001, and remained different until postoperative day 4 (experimental 2.33 mg/dL vs control 2.26 mg/dL, p = 0.24). Atrial appendage and strap muscle were analyzed after the first bolus and after revascularization. There were no differences between groups in tissue magnesium or calcium. Urinary magnesium was elevated in the experimental (experimental 324.5 mg/24 hours, vs control 45.1 mg/24 hours, p = 0.01). Calcium excretion was higher (experimental 370 mg/24 hours vs control 186 mg/24 hours, p < 0.001) and was associated with lower serum calcium. Serum calcium was higher in the control through the fourth postoperative day. The incidence of atrial fibrillation was experimental 32 of 105 (30.5%) versus control 41 of 97 (42.3%) p = 0.08. Atrial fibrillation was different on the first postoperative day (experimental 3/105, 2.9% vs control 9/97, 9.3%), p = 0.05.

CONCLUSIONS

Overall prophylactic magnesium supplementation does not significantly reduce atrial and ventricular arrhythmias. The only significant benefit of magnesium supplementation was on the first postoperative day.

Predictors of pericardial effusion after orthotopic heart transplantation

OBJECTIVES

Pericardial effusion occurs frequently after orthotopic heart transplantation, but the causes of this complication have not been well described. This study was designed to identify factors predisposing toward the development of significant postoperative pericardial effusions in a large, single-institution population of orthotopic heart transplant recipients.

METHODS

A retrospective review of more than 90 preoperative, intraoperative, and postoperative variables was conducted for 241 patients undergoing orthotopic heart transplantation from September 1988 to December 1999. Patients who had significant postoperative pericardial effusions develop were identified from postoperative echocardiograms by standard criteria. Factors associated with the development of significant pericardial effusions were determined by multivariate logistic regression analysis.

RESULTS

Echocardiographic data were available for 203 of 241 transplant recipients. Forty-two patients (21%) had significant effusions develop. According to multivariate analysis, pericardial effusions were less likely to occur in recipients with a history of previous cardiac surgery (odds ratio 0.13, 95% confidence interval 0.05-0.36, P <.0001) and with greater weight (odds ratio 0.96, 95% confidence interval 0.94-0.99, P <.0048). Pericardial effusions were more likely to occur in patients who had received aminocaproic acid during the operation (odds ratio 5.92, 95% confidence interval 2.23-15.72, P <.0008). Patient survival and hospital length of stay did not differ between patients with and without postoperative pericardial effusions.

CONCLUSIONS

Postoperative pericardial effusions develop in approximately 20% of patients undergoing orthotopic cardiac transplantation. On the basis of the risk factors identified in this study, prevention may prove difficult, although avoidance of the intraoperative use of aminocaproic acid may be helpful.

Long-term follow-up of pacing of the conditioned diaphragm in quadriplegia

The authors have previously shown that conditioning of the diaphragm for continuous bilateral pacing is a feasible and effective means of ventilation in patients with complete respiratory paralysis from high cervical (above C3) quadriplegia. The present study reports the long-term results of continuous diaphragmatic pacing. Twelve quadriplegia patients underwent bilateral phrenic nerve pacemaker placement and diaphragm conditioning from 1981 to 1987. Pacing was initiated at 11 Hz and progressively decreased to 7.1 Hz. A pulse train duration of 1.3 seconds for adults and 0.9 seconds for children was used. Long-term follow-up information obtained included pacing status (full-time, part-time, or mechanical ventilation), ventilation parameters, and social circumstances. Of the 12 patients, 6 continued to pace full time (mean 14.8 years); all were living at home. Three patients paced for an average of 1.8 years before stopping; two were institutionalized. One patient who paced full time for 6.5 years before lapsing to part time, lived at home. Two patients were deceased; one paced continuously for 10 years before his demise, the other stopped pacing after 1 year. Patients who stopped full-time pacing did so mainly for reasons of inadequate social or financial support or associated medical problems. All patients demonstrated normal tidal volumes and arterial blood gases while pacing full time. Despite theoretical concerns about long-term nerve damage, no patient lost the ability to pace the phrenic nerve. Threshold currents did not increase over time (original/follow-up: 0.46/0.47 for right, 0.45/0.46 for left), nor did maximal currents (original/follow-up: 1.16/1.14 for right, 1.37/1.26 for left). This follow-up confirms that quadriplegic patients are able to meet long-term, full-time ventilation requirements using phrenic nerve stimulation of the conditioned diaphragm. Careful review of diaphragmatic pacing candidates with respect to associated medical conditions, social support, and motivation is essential for appropriate patient selection and successful long-term results.

Experimental confirmation of effectiveness of fenestration in acute aortic dissection

BACKGROUND

Aortic fenestration is used clinically to treat organ ischemia in acute descending aortic dissection. However, fenestration has not been studied experimentally. This study does so using an animal model.

METHODS

Descending aortic dissection was created in six dogs, with subsequent fenestration of the infrarenal aorta. Blood flow (femoral, cephalic, and renal), blood pressure (femoral and carotid), and aortic distensibility were measured at baseline, after dissection, and after fenestration. Values were compared using paired t tests.

RESULTS

Baseline femoral, cephalic, and renal arterial flows were 53+/-37, 78+/-65, and 83+/-52 mL/min, respectively. Baseline femoral and carotid pressures were 82+/-13 and 81+/-11 mm Hg, respectively. After dissection, femoral, cephalic, and renal arterial flow decreased to 20+/-21 (p < 0.05), 38+/-26, and 56+/-36 mL/min, respectively. Femoral blood pressure decreased to 28+/-17 mm Hg (p < 0.05). With fenestration, femoral, cephalic, and renal flows increased to 60+/-37 (p < 0.05), 78+/-51, and 80+/-48 mL/min, respectively. Femoral blood pressure increased to 85+/-28 mm Hg (p < 0.05). Carotid pressure remained unchanged with dissection and fenestration (77+/-17 mm Hg, 82+/-17 mm Hg, respectively). Baseline aortic distensibility (21%) decreased significantly after dissection (to 1.4%, p < 0.05) and increased after fenestration (to 12%, p < 0.05).

CONCLUSIONS

Experimental aortic fenestration restored blood pressure and flow to hypoperfused organs in acute descending aortic dissection. The continued clinical application of fenestration is supported.

Diaphragm pacing

Diaphragm pacing is an established mode of ventilation for patients with upper motor neuron injury and preserved phrenic nerve function. Careful patient evaluation with regard to phrenic nerve function, motivation, and adequate psychosocial support is paramount for successful pacing. In properly selected individuals, full-time continuous bilateral pacing for several years has been demonstrated with advantages of increased independence and productivity, fewer tracheal tube complications, and improved phonation. Ongoing research in the field of diaphragm pacing includes refinements in electrode placement and continued testing of totally implantable devices.

Trends in the incidence of upper extremity soft tissue malignancies: a 40-year review of the Connecticut State Tumor Registry

BACKGROUND

Although soft tissue malignancies of the upper extremity are rare, the management of these lesions has been controversial and the etiologic factors associated with the occurrence of these tumors are not well understood. The purpose of this study was to identify possible epidemiologic factors related to a recently noted rise in the occurrence of these tumors in the state of Connecticut.

METHODS

The occurrence of upper extremity soft tissue tumors over the past 40 years was reviewed in the Connecticut State Tumor Registry. Demographic data collected included occupational history, residence, and presence of concomitant malignancies. Tumor histology, the extent of resection, and the incidence of recurrences were also noted. Factors associated with recurrence were identified using linear regression analysis.

RESULTS

During the 40-year study period, 359 patients having upper extremity soft tissue tumors were entered into the Connecticut State Tumor Registry. An increasing trend in the number of upper extremity soft tissue tumors was evident. Many patients were involved in heavy industry or related fields. Fibrosarcoma and liposarcoma were the most common tumor types, occurring in 111 (30.3%) and 48 patients (13.2%), respectively. Sixty-seven patients presented with a synchronous second primary malignancy of the breast (49 patients), lung (seven patients), or gastrointestinal tract (five patients). Most patients (69.9%) underwent local excision of the soft tissue tumors, with fewer undergoing wide excision (20.3%) or radical excision (9.7%). Recurrence, which occurred in 144 patients, was found to be associated with extent of resection, occupational history, and concomitant malignancy. Delineation of such risk factors may be helpful in identifying patients in whom aggressive management may decrease recurrence and improve survival.

Use of neodymium yttrium aluminum garnet laser in long-term palliation of airway obstruction

Palliation of acute airway obstruction using the neodymium yttrium aluminum garnet (Nd-YAG) laser was studied in 54 patients who presented over a 42-month period to the Yale cardiothoracic surgery service. Thirty-seven patients had bronchogenic carcinoma; 27 had stage IIIB or IV disease. Nine patients had endobronchial metastases from a primary nonbronchogenic carcinoma. Eight patients had benign disease. A total of 109 Nd-YAG laser tumor ablations were performed. In addition, 32 patients underwent postoperative brachytherapy. Median survival for all patients was 12 months. Patients with bronchogenic carcinoma had a median survival of five months. Fifteen of 20 patients (75%) alive at the time of follow-up reported continued palliation as shown by an improved postoperative Karnofsky score. There was no survival benefit from Nd-YAG laser ablation of endobronchial bronchogenic carcinoma; however, the Nd-YAG laser provided good to excellent palliation in the majority of patients on long-term follow-up.

PYY inhibition of VIP-stimulated ion transport in the rabbit distal ileum

Vasoactive intestinal polypeptide (VIP) is the pathophysiologic mediator of several small intestinal hypersecretion states. VIP exerts its effect by binding mucosal receptors and ultimately increasing intracellular levels of cAMP. Peptide YY (PYY), a GI hormone concentrated in the distal ileum and colon, has been demonstrated to decrease VIP-mediated secretion in the colon through a specific Y4 mucosal receptor. Characterization of PYY's effect on VIP-stimulated small intestinal secretion may provide a basis for future therapeutic interventions. We hypothesized that ion transport in the small intestine is mediated through a novel Y receptor subtype. We performed Ussing chamber ion transport studies on rabbit ileum using VIP, PYY, and other pancreatic polypeptide (PP)-fold peptides in order to specifically examine: (1) the effects of VIP and PYY on basal and VIP-stimulated short circuit current (Isc), and (2) the changes in VIP-stimulated Isc in response to NPY, PP, leucine31,proline31 neuropeptide Y fragment, ([Leu31,Pro34]NPY) and the carboxy-terminal fragment of NPY (NPY13-36). VIP increased basal Isc in a concentration-dependent manner, while PYY decreased basal Isc. Graded concentrations of PYY decreased VIP-stimulated increases in Isc. PYY added prior to VIP had no effect on VIP-stimulated increases in ISC. Inhibition of VIP-stimulated Isc increases was seen with NPY, but not with [Leu31,Pro34]NPY, PP, or NPY13-36. This distinct pattern of binding affinity characterizes a novel Y receptor subtype. Additionally, increases in Isc by VIP despite pretreatment with PYY suggests that VIP-stimulated ion transport is mediated through mechanisms other than increases in cAMP.