Improvement in gastrointestinal bleeding after septal myectomy for hypertrophic cardiomyopathy.

OBJECTIVE: Patients with obstructive hypertrophic cardiomyopathy may have occult gastrointestinal bleeding. In this study, we analyzed outcomes of septal myectomy in patients who had a history of gastrointestinal bleeding preoperatively to understand patient characteristics and impact of septal reduction on recurrent gastrointestinal bleeding. METHODS: We analyzed 73 adult patients who had a history of gastrointestinal bleeding before transaortic septal myectomy for obstructive hypertrophic cardiomyopathy and compared outcomes to 219 patients without gastrointestinal bleeding preoperatively. RESULTS: Patients with preoperative history of gastrointestinal bleeding were older (median (IQR) age, 65 (59-69) years, P < .001) and were more likely to have systemic hypertension (70% vs 53%, P = .020) and coronary artery disease (25% vs 13%, P = .026). Preoperatively, patients with gastrointestinal bleeding had a larger left atrial volume index (median, 53 mL/m2; interquartile range, 42-67; P = .006) and greater right ventricular systolic pressure (median, 36 mm Hg; interquartile range, 32-49; mm Hg, P = .005) but no significant difference in severity of outflow tract obstruction (P = .368). There were no perioperative deaths. The estimated 5- and 10-year survivals were 96.6% and 81.8%, respectively. At a median of 3.4 (interquartile range, 1.9-9.1) years after septal myectomy, 11 patients (15%) had recurrence of gastrointestinal bleeding, which was attributed to angiodysplasia or unknown causes in 6 patients (8%). CONCLUSIONS: Patients with a preoperative history of gastrointestinal bleeding have favorable short- and long-term outcomes after septal myectomy for obstructive hypertrophic cardiomyopathy. Remission of gastrointestinal bleeding was observed in 85% of patients postprocedure, and only 8% of the patients had recurrent gastrointestinal bleeding due to angiodysplasia or unknown causes.

Preoperative echocardiography as a prognostic tool for liver transplant in patients with hypertrophic cardiomyopathy.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) presents with a hypertrophied left ventricle (LV). It is often associated with LV outflow tract obstruction (LVOTO) and a risk for sudden death. This study aimed to describe outcomes of patients with HCM who underwent liver transplant (LT). METHODS: A retrospective review was conducted for patients diagnosed with HCM undergoing LT. Patient characteristics, preoperative echocardiography results, HCM risk of sudden cardiac death prediction model score, and 5-year mortality were examined. A univariable Cox proportional hazards model was used to evaluate the association between risk factors and 5-year mortality. All tests were two-sided with the alpha level set at .05. RESULTS: Twenty-nine patients were included in the analysis. Six patients (21%) had a perioperative cardiopulmonary complication. The 5-year survival rate was 61% (95% CI, 45-82). The analyzed risk factors showed that 5-year post-LT survival was significantly predicted by maximal LV outflow tract gradient at rest > 60 mmHg (hazard ratio, 1.04 [95% CI, 1.01-1.06]). CONCLUSIONS: Preoperative LV outflow tract resting gradient > 60 mmHg was associated with 5-year post-LT mortality. The results suggest the severity of LVOTO identified by echocardiography is a prognostic tool for patients with HCM after LT.

Effect of Intensive Blood Pressure Lowering on the Risk of Atrial Fibrillation.

It remains uncertain whether intensive control of blood pressure (BP) results in a lower risk of atrial fibrillation (AF) in patients with hypertension. Using data from SPRINT (Systolic Blood Pressure Intervention Trial), which enrolled participants with hypertension at increased risk of cardiovascular disease, we examined whether intensive BP lowering (target systolic BP [SBP] <120 mm Hg), compared with standard BP lowering (target SBP<140 mm Hg), results in a lower risk of AF. This analysis included 8022 participants (4003 randomized to the intensive arm and 4019 to standard BP arm) who were free of AF at the time of enrollment and with available baseline and follow-up electrocardiographic data. AF was ascertained from standard 12-lead electrocardiograms recorded at biannual study examinations and an exit visit. During up to 5.2 years of follow-up and a total of 28 322 person-years, 206 incident AF cases occurred; 88 in the intensive BP-lowering arm and 118 in the standard BP-lowering arm. Intensive BP lowering was associated with a 26% lower risk of developing new AF (hazard ratio, 0.74 [95% CI, 0.56-0.98]; P=0.037). This effect was consistent among prespecified subgroups of SPRINT participants stratified by age, sex, race, SBP tertiles, prior cardiovascular disease, and prior chronic kidney disease when interactions between treatment effect and these subgroups were assessed using Hommel adjusted P values. In conclusion, intensive treatment to a target of SBP <120 mm Hg in patients with hypertension at high risk of cardiovascular disease has the potential to reduce the risk of AF. Registration- URL: https://www.clinicaltrials.gov; Unique identifier: NCT01206062.

Heyde Syndrome: Aortic Stenosis and Beyond.

Heyde described aortic stenosis and gastrointestinal bleeding in the 1950s. Since then, a link with intestinal angiodysplasia and abnormalities of von Willebrand factor (VWF) has been noted. Loss of the highest-molecular-weight multimers of VWF and bleeding also have been described in subaortic stenosis in hypertrophic cardiomyopathy, in isolated mitral and aortic insufficiency, in endocarditis, in patients with prosthetic valve stenosis or regurgitation, and in patients with left ventricular assist devices (LVADs). Bleeding tends to recur with local treatment of angiodysplasias, whereas cardiac repair or removal of LVAD eliminates VWF dysfunction is curative of bleeding in the majority.

Periprocedural Stroke and Myocardial Infarction as Risks for Long-Term Mortality in CREST.

BACKGROUND: The Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) previously reported increased mortality in patients who sustained a periprocedural stroke or cardiac event (myocardial infarction [MI] or biomarker only) in follow-up to 4 years. We now extend these observations to 10 years. METHODS AND RESULTS: CREST is a randomized controlled trial designed to compare the outcomes of carotid stenting versus carotid endarterectomy. Proportional hazards models were used to assess the association between mortality and periprocedural stroke, MI, or biomarker-only events. For 10-year follow-up, patients with periprocedural stroke were at 1.74× the risk of death compared with those without stroke (adjusted hazard ratio [HR]=1.74; 95% CI, 1.21-2.50; P<0.003). This increased risk was driven by increased early (between 0 and 90 days) mortality (adjusted HR=14.41; 95% CI, 5.33-38.94; P<0.0001), with no significant increase in late (between 91 days and 10 years) mortality (adjusted HR=1.40; 95% CI, 0.93-2.10; P=0.11). Patients with a protocol MI were at 3.61× increased risk of death compared with those without MI (adjusted HR=3.61; 95% CI, 2.28-5.73; P<0.0001), with an increased hazard both early (adjusted HR=8.20; 95% CI, 1.86-36.2; P=0.006) and late (adjusted HR=3.40; 95% CI, 2.09-5.53; P<0.0001). Patients with a biomarker-only event were at 2.04× increased risk overall (adjusted HR=2.04; 95% CI, 1.09-3.84; P=0.03) than those without MI, with an increased early hazard (adjusted HR=8.44; 95% CI, 1.09-65.5; P=0.04) and a suggestive but nonsignificant association toward higher 91-day to 10-year risk (1.88; 95% CI, 0.97-3.64; P=0.062) contributing to the increased risk. CONCLUSIONS: In the CREST trial, patients with periprocedural events demonstrate a substantial increase in future mortality to 10 years. For stroke, this risk is largely confined to an early time frame while periprocedural MI or biomarker-only events confer a continuous increased mortality for 10 years. Strategies to reduce periprocedural events and to optimize the evaluation and management of patients with cardiac events should be considered in efforts to reduce not only early but also long-term mortality. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov . Unique identifier: NCT00004732.

Von Willebrand factor multimer quantitation for assessment of cardiac lesion severity and bleeding risk.

BACKGROUND: von Willebrand factor (VWF) multimer quantitation has been utilized in the assessment of valvular heart disease, however, there is no standardized method for quantitation. We compared three methods of assessment which utilized a normal plasma control. METHODS: We analyzed 476 samples and their control plasma from 368 patients with valvular heart disease, hypertrophic cardiomyopathy, or LVAD therapy, and 27 normal subjects. VWF multimers were assessed as normalized VWF multimer ratios (NMR) of gel bands >15/2-15 (NMR15) or gel bands >10/2-10 (NMR10). Associations of VWF laboratory and multimeric assessments with cardiac lesion severity and acquired bleeding were investigated. RESULTS: Abnormal multimers were present in 78% of patients with moderate to severe hemodynamic abnormalities compared to 19% of patients with normal or mildly abnormal hemodynamics. NMR showed strong association with severe cardiac lesions (NMR15: OR 15.29, CI 9.04-27.18; NMR10: OR 14.18, CI 8.88-23.21). PFA-CADP was strongly associated with moderate to severe cardiac lesions (OR 14.91, CI 9.08-24.50). PFA-CADP and NMR15 showed excellent ability to discriminate ≥moderate (AUC 0.86, CI 0.83-0.89 and 0.83, CI 0.79-0.87 respectively) and severe cardiac lesions (AUC 0.84, CI 0.81-0.88 and 0.85, CI 0.81-0.88 respectively). NMR was less strongly associated with bleeding (OR 4.01 for NMR10, CI 2.49-6.58). CONCLUSION: Quantification of VWF multimers may provide clinical utility in circumstances where clinical estimation of cardiac lesion severity is challenging, such as with dysfunctional prosthetic valves. The presence of abnormal VWF multimers is associated with bleeding, however further quantitation provided only modest improvement in risk stratification.

Impact of Intensive Versus Standard Blood Pressure Management by Tertiles of Blood Pressure in SPRINT (Systolic Blood Pressure Intervention Trial).

Intensive systolic blood pressure (SBP) control improved outcomes in SPRINT (Systolic Blood Pressure Intervention Trial). Our objective was to expand on reported findings by analysis of baseline characteristics, primary outcomes, adverse events, follow-up blood pressure, and medication use differences by baseline SBP (tertile 1 [T1], <132; tertile 2 [T2], 132-145; and tertile 3 [T3], >145 mm Hg). Participants with higher baseline SBP tertile were more often women and older, had higher cardiovascular risk, and lower utilization of antihypertensive medications, statins, and aspirin. Achieved SBP in both treatment arms was slightly higher in T2 and T3 compared with T1 and fewer in the T3 groups achieved SBP targets compared with T1 and T2 groups. The primary composite outcome with intensive versus standard SBP treatment was reduced by 30% in T1, 23% in T2, and 17% in T3 with no evidence of an interaction (P=0.77). Event rates were lower in the intensive arm, and there was no evidence that this benefit differed by SBP tertile. There was no difference in the hazard for serious adverse events in any of the 3 tertiles. Medication utilization differed across the SBP tertiles at baseline with a lesser percentage of diuretics and angiotensin-converting enzyme inhibitors/angiotensin receptor blocker drugs in the higher tertiles-a finding that reversed during the trial. The beneficial effects of intensive SBP lowering were not modified by the level of baseline SBP. Within the parameters of this population, these findings add support for clinicians to treat blood pressure to goal irrespective of baseline SBP.

Acute Cardiac Complications in Critical Brain Disease.

Acute cardiac complications in critical brain disease should be understood as a clinical condition representing an intense brain-heart crosstalk and might mimic ischemic heart disease. Two main entities (neurogenic stunned myocardium [NSM] and stress cardiomyopathy) have been better characterized in the neurocritically ill patients and they portend worse clinical outcomes in these cases. The pathophysiology of NSM remains elusive. However, significant progress has been made on the early identification of neurocardiac compromise following acute critical brain disease. Effective prevention and treatment interventions are yet to be determined.

Platelet Function Analyzer 100 and Brain Natriuretic Peptide as Biomarkers in Obstructive Hypertrophic Cardiomyopathy.

To test dual blood biomarkers compared with electrocardiogram (ECG) for hypertrophic cardiomyopathy (HC) screening, we performed 3 analyses and cut-point assessments. First, we measured platelet function analyzer (PFA)-100 (n = 99) and normalized B-type natriuretic peptide (BNP) or NT-proBNP (BNP/upper limit of normal [ULN], n = 92) in 64 patients with HC and 29 normal controls (NCs). Second, from the regression equation between PFA and gradient (r = 0.77), we derived estimated PFA in a population of 189 patients with functional class I HC in whom measured BNP/ULN and ECG were available, and calculated single and dual biomarker sensitivity and specificity compared with ECG. Finally, we compared BNP/ULN in class I patients based on mutation and familial history status. In 42 patients with obstructive HC versus NCs, there was a slight overlap of PFA and BNP/ULN, but for the product of PFA × BNP/ULN, there was near-complete separation of values. Among patients with class I obstructive HC, estimated PFA × BNP/ULN had a sensitivity of 93% and a specificity of 100%; in latent and nonobstructive HC, sensitivity dropped to 61% and 72%; for ECG in obstructive, latent, and nonobstructive HC, sensitivity was 71%, 34%, and 67%. Functional class I patients with positive (n = 28) and negative (n = 36) sarcomere mutations and a positive (n = 71) or a negative (n = 109) family history had significant elevations of BNP/ULN versus NC, with no between-group differences. In conclusion, PFA and BNP were highly associated with obstructive HC and could potentially be used for screening; BNP was not uniquely elevated in patients with familial versus nonfamilial or mutation-positive versus mutation-negative HC.

Gastrointestinal Bleeding in Native and Prosthetic Valve Disease.

Gastrointestinal bleeding with severe aortic stenosis was originally described in the 1950s by Heyde, although for years, the association was debated. Further discovery of mechanisms and the ubiquity and severity of acquired von Willebrand syndrome in the left ventricular assist device therapy have removed any doubts. At this time, gastrointestinal bleeding from intestinal angiodysplasia in patients with turbulence-related proteolysis of the highest molecular weight multimers of von Willebrand factor is now known to occur in patients with aortic stenosis, and also subaortic obstruction and associated mitral insufficiency in hypertrophic cardiomyopathy, isolated mitral and aortic insufficiency, endocarditis, and in patients with prosthetic valve dysfunction, either from stenosis or insufficiency. The degree of loss of high molecular weight multimers correlates with lesion severity, and tests of von Willebrand factor function have been proposed as important biomarkers of the severity of valve dysfunction, including in-lab testing for paravalvular leak during transcatheter aortic valve replacement. Bleeding tends to recur after endoscopic or surgical therapy, but cardiac repair is curative in the great majority.

Acute Cardiac Complications in Critical Brain Disease.

Acute cardiac complications in critical brain disease should be understood as a clinical condition representing an intense brain-heart crosstalk and might mimic ischemic heart disease. Two main entities (neurogenic stunned myocardium [NSM] and stress cardiomyopathy) have been better characterized in the neurocritically ill patients and they portend worse clinical outcomes in these cases. The pathophysiology of NSM remains elusive. However, significant progress has been made on the early identification of neurocardiac compromise following acute critical brain disease. Effective prevention and treatment interventions are yet to be determined.

High-Sensitivity Troponin T and NT-proBNP Kinetics in Breast Cancer Chemotherapy.

BACKGROUND/AIMS: Doxorubicin (DOX) and trastuzumab (TRA) are associated with cardiac dysfunction. METHOD: High-sensitivity troponin T (hs-TnT) and brain natriuretic peptide attached to the amino acid N-terminal fragment in the prohormone (NT-proBNP) were measured before and on days +1, +2, +3, and +7 during cycles 1 and 2 of therapy with DOX or TRA in breast cancer patients. RESULTS: Five of eleven DOX-treated women, compared with 2/11 TRA-treated women, had undetectable baseline hs-TnT. By day +1 of cycle 2, all the DOX-treated women (p = 0.03) but only 7/11 TRA-treated women (p = ns) had detectible hs-TnT. Time to peak was 1-2 days for both groups. In the DOX-treated women, hs-TnT showed significant peaks from precycle baseline, increases in precycle 1 to precycle 2 levels, and a cycle 1 to cycle 2 peak and area under the curve (AUC). hs-TnT increased from precycle (1, 4.6 ± 6.3 pg/mL) to a cycle 2 peak of 16.1 ± 15.0 pg/mL (p < 0.002). No increases were seen with the TRA treatment. Transient posttreatment increases in NT-proBNP were seen after both therapies. CONCLUSION: DOX was associated with increased pretreatment baseline, peak, and AUC hs-TnT levels. Both DOX and TRA acutely perturb NT-proBNP. Assessment of pre- and posttreatment hs-TnT could be a means of quantifying cumulative myocardial injury in the course of chemotherapy.

von Willebrand Factor Abnormalities and Heyde Syndrome in Dysfunctional Heart Valve Prostheses.

IMPORTANCE: Limited data suggest that von Willebrand factor (VWF) abnormalities may accompany the high-shear state associated with prosthetic valve dysfunction. If true, laboratory testing could add value in quantifying prosthesis dysfunction and could suggest a pathophysiological explanation for acquired bleeding in some patients. OBJECTIVES: To determine whether dysfunctional valve prostheses are associated with VWF abnormalities compared with normally functioning valve prostheses, to identify the severity of the VWF abnormality relative to other conditions, and to describe associated bleeding and the occurrence of gastrointestinal angiodysplasia. DESIGN, SETTING, AND PARTICIPANTS: Cohort study in a multispecialty practice setting from August 2010 through November 2015. To assess the severity of VWF dysfunction, data were compared with those from previously reported healthy controls and patients with aortic stenosis, mitral regurgitation, and left ventricular assist devices. Patients underwent assessment of multiple VWF laboratory tests and echocardiography. MAIN OUTCOMES AND MEASURES: Loss of high-molecular-weight multimers of VWF. RESULTS: A total of 136 patients were included in this study. During the study period, we assessed 26 patients with normally functioning surgical or transcatheter aortic valve replacement, 24 patients with dysfunctional aortic valve replacement, 36 patients with normally functioning mitral valve replacement or repair, 19 patients with dysfunctional mitral valve replacement or repair, and 31 patients with native aortic regurgitation without coexisting aortic stenosis. von Willebrand factor multimers were abnormal in 1 of 26 normal aortic valve replacements and in 2 of 36 normal mitral valve replacements or repairs but were abnormal in 20 of 24 dysfunctional aortic valve replacements and in 14 of 19 dysfunctional mitral valve replacements or repairs (P < .001 for both). Normal aortic valve replacement also had a higher VWF activity to antigen ratio, mean (range) 0.94 (0.84-0.99) compared to dysfunctional aortic valve replacement, 0.78 (0.73-0.87), P < .001, as did normal mitral valve replacement or repair, 0.90 (0.86-0.93) compared to dysfunctional mitral valve replacement or repair, 0.78 (0.70-0.90), P = .005. Platelet function analyzer closure times were lower with normal aortic valve replacement, mean (range) 92 (82-112) seconds compared to dysfunctional aortic valve replacement, 139 (122-177) seconds, P < .001, and also in normally functioning mitral valve replacement or repair, 85 (74-96) seconds compared to dysfunctional mitral valve replacement or repair, 143 (128-192) seconds, P < .001. Gastrointestinal bleeding was noted in 6 of 24 patients with aortic prosthesis dysfunction and in 5 of 19 patients with mitral prosthesis/repair dysfunction and was associated with a lower normalized VWF multimer ratio than in patients without bleeding. Gastrointestinal angiodysplasia was noted in 5 of 6 bleeding patients with dysfunctional aortic prostheses and in 3 of 5 bleeding patients with dysfunctional mitral prostheses/repair. CONCLUSIONS AND RELEVANCE: Acquired abnormalities of VWF multimers are associated with aortic and mitral prosthesis dysfunction, with occasional gastrointestinal bleeding and gastrointestinal angiodysplasia. Quantitative VWF tests may provide adjunctive value in the difficult assessment of prosthetic valve dysfunction.

Anesthetic type and risk of myocardial infarction after carotid endarterectomy in the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST).

OBJECTIVE: Carotid endarterectomy (CEA) is usually performed under general anesthesia (GA), although some advocate regional anesthesia (RA) to reduce hemodynamic instability and allow neurologic monitoring and selective shunting. RA does not reduce risk of periprocedural stroke or death, although some series show a reduction in myocardial infarction (MI). We investigated the association of anesthesia type and periprocedural MI among patients receiving GA or RA for CEA and patients undergoing carotid artery stenting (CAS) in the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST). METHODS: Between 2000 and 2008, 1151 patients underwent CEA (anesthetic type available for 1149 patients), and 1123 patients underwent CAS ≤30 days of randomization in CREST. CEA patients were categorized by anesthetic type (GA vs RA). CREST defined protocol MI as chest pain or electrocardiogram change plus biomarker evidence of MI, and total MI was defined as protocol MI plus biomarker-positive (+)-only MI. The incidence of protocol MI and total MI in patients undergoing CEA under GA and RA were compared with those undergoing CAS. Other study end points were similarly compared. Differences in baseline characteristics and periprocedural events were evaluated among the three groups. Logistic regression, adjusting for age and symptomatic status, was used to assess group differences. RESULTS: The three groups had similar demographic risk factors, except for prevalence of symptomatic carotid stenosis, which was lowest in the CEA-RA group (P = .03). Of the 111 patients in the CEA-RA group, no protocol MIs occurred and only two biomarker+-only MIs, for an overall incidence of 1.8%, similar to the 1.7% overall incidence in patients undergoing CAS. In contrast, the combined incidence of protocol and biomarker+-only MIs in the 1038 patients in the CEA-GA group was significantly higher at 3.4% (P = .04), twice the risk of protocol MI and biomarker+-only MI compared with those undergoing CAS (odds ratio [OR], 2.01; 95% confidence interval [CI], 1.14-3.54). Direct comparison of the MI incidence between CEA-RA and CEA-GA showed no statistical difference. Patients undergoing CEA-GA had lower odds of a periprocedural stroke (OR, 0.48; 95% CI, 0.28-0.79) and stroke or death (OR, 0.46; 95% CI, 0.27-0.76) compared with those undergoing CAS but were not significantly different from those undergoing CEA-RA. CONCLUSIONS: Patients in CREST undergoing CEA-RA had a similar risk of periprocedural MI as those undergoing CAS, whereas the risk for CEA-GA was twice that compared with patients undergoing CAS. Nevertheless, because periprocedural MI is one of the few variables favoring CAS over CEA and has been associated with decreased long-term survival, RA should be seriously considered for patients undergoing CEA.

Usefulness of Von Willebrand Factor Activity Indexes to Predict Therapeutic Response in Hypertrophic Cardiomyopathy.

Degraded by shear stress, loss of high-molecular-weight multimers of von Willebrand factor (VWF) correlates strongly with pressure gradient in aortic stenosis (AS) and obstructive hypertrophic cardiomyopathy (HC). We assessed VWF tests before and after interventions in HC and contrasted the severity of abnormalities in HC to patients with AS, mitral regurgitation, and left ventricular assist devices. Ninety patients with median (interquartile range) age 66 (53 to 72) years, 51% men, with HC had assessments of 3 VWF parameters and B-type natriuretic peptide before and after 26 discreet medical/pacing interventions, 22 alcohol septal ablations, and 28 ventricular septal myectomies. VWF multimers were abnormal in 87% of patients with obstructive HC versus 48% of patients with latent obstruction (p = 0.0001). VWF measurements correlated with peak instantaneous left ventricular outflow tract gradient, Spearman ρ 0.51 to 0.61, p <0.0001. For B-type natriuretic peptide, correlation with left ventricular outflow tract gradient was weaker, ρ = 0.37, p = 0.0005, but stronger with septal thickness or mitral E/e'. In pre-/post-medical treatment of HC, VWF multimers were abnormal in 73%/68% of patients, p = 0.74; pre-/post-septal ablation 74%/26%, p = 0.0035; and pre-/post-septal myectomy 75%/0%, p <0.0001. In obstructive HC, the degree VWF multimer loss was greater than in severe AS or severe mitral regurgitation and overlapped that seen in left ventricular assist devices. In conclusion, VWF activity indexes were predictably abnormal in patients with HC with resting obstruction to a degree where bleeding could be anticipated, accurately reflected gradient changes after intervention, and demonstrated complete normalization after septal myectomy.

Atrioventricular Sequential Pacing for Hypertrophic Cardiomyopathy During Liver Transplantation.

Hypertrophic cardiomyopathy is a myocardial disorder that carries an increased risk of morbidity and mortality during liver transplantation. We describe the use of atrioventricular sequential pacing, placed preoperatively, to assist with intraoperative management of a patient with severe refractory hypertrophic cardiomyopathy undergoing orthotopic piggyback liver transplantation. We discuss the pathogenesis and treatment of this infrequent but serious comorbidity.