Utility of gene expression profiling score variability to predict clinical events in heart transplant recipients

BACKGROUND

Gene expression profiling test scores have primarily been used to identify heart transplant recipients who have a low probability of rejection at the time of surveillance testing. We hypothesized that the variability of gene expression profiling test scores within a patient may predict risk of future events of allograft dysfunction or death.

METHOD

Patients from the IMAGE study with rejection surveillance gene expression profiling tests performed at 1- to 6-month intervals were selected for this cohort study. Gene expression profiling score variability was defined as the standard deviation of an individual's cumulative test scores. Gene expression profiling ordinal score (range, 0-39), threshold score (binary value=1 if ordinal score ≥ 34), and score variability were studied in multivariate Cox regression models to predict future clinical events.

RESULTS

Race, age at time of transplantation, and time posttransplantation were significantly associated with future events in the univariate analysis. In the multivariate analyses, gene expression profiling score variability, but not ordinal scores or scores over threshold, was independently associated with future clinical events. The regression coefficient P values were <0.001, 0.46, and 0.773, for gene expression profiling variability, ordinal, and threshold scores, respectively. The hazard ratio for a 1 unit increase in variability was 1.76 (95% CI, 1.4-2.3).

DISCUSSION

The variability of a heart recipient's gene expression profiling test scores over time may provide prognostic utility. This information is independent of the probability of acute cellular rejection at the time of testing that is rendered from a single ordinal gene-expression profiling test score.

Remission of chronic anthracycline-induced heart failure with support from a continuous-flow left ventricular assist device

We report the case of a patient who had chronic anthracycline-induced cardiomyopathy that was reversed after treatment with a left ventricular assist device. A 29-year-old woman had undergone anthracycline-based chemotherapy as a teenager in 1991 and 1992 and received a diagnosis of dilated cardiomyopathy 10 years later. Optimal medical therapy had initially controlled the symptoms of heart failure. However, in June 2006, the symptoms worsened to New York Heart Association functional class IV status. We implanted a continuous-flow left ventricular assist device as a bridge to cardiac transplantation; of note, a left ventricular core biopsy at that time showed no replacement fibrosis. The patient's clinical status improved thereafter, enabling left ventricular assist device ex-plantation after 17 months. To our knowledge, this is the first report of the use of left ventricular assist device support to reverse chronic anthracycline-induced heart failure.

Arteriovenous malformation and gastrointestinal bleeding in patients with the HeartMate II left ventricular assist device

BACKGROUND

In this study we investigated gastrointestinal (GI) bleeding and its relationship to arteriovenous malformations (AVMs) in patients with the continuous-flow HeartMate II (HMII) left ventricular assist device (LVAD).

METHODS

The records of 172 patients who received HMII support between November 2003 and June 2010 were reviewed. Patients were considered to have GI bleeding if they had 1 or more of the following symptoms: guaiac-positive stool; hematemesis; melena; active bleeding at the time of endoscopy or colonoscopy; and blood within the stomach at endoscopy or colonoscopy. The symptom(s) had to be accompanied by a decrease of >1 g/dl in the patient's hemoglobin level. The location of the bleeding was identified as upper GI tract, lower GI tract or both according to esophagogastroduodenoscopy, colonoscopy, small-bowel enteroscopy or mesenteric angiography. Post-LVAD implantation anti-coagulation therapy consisted of warfarin, aspirin and dipyridamole.

RESULTS

Thirty-two of the 172 patients (19%) had GI bleeding after 63 ± 62 (range 8 to 241) days of HMII support. Ten patients had GI bleeding from an AVM; these included 3 patients who had 2 bleeding episodes and 2 patients who had 5 episodes each. Sixteen patients had upper GI bleeding (10 hemorrhagic gastritis, 4 gastric AVM, 2 Mallory-Weiss syndrome), 15 had lower GI bleeding (6 diverticulosis, 6 jejunal AVM, 1 drive-line erosion of the colon, 1 sigmoid polyp, 1 ischemic colitis) and 1 had upper and lower GI bleeding (1 colocutaneous and gastrocutaneous fistula). All GI bleeding episodes were successfully managed medically.

CONCLUSIONS

Arteriovenous malformations can cause GI bleeding in patients with continuous-flow LVADs. In all cases in this series, GI bleeding was successfully managed without the need for surgical intervention.

Thrombotic occlusion of an aortic-root xenograft during left ventricular assistance

A 45-year-old man underwent repair of a congenital bicuspid aortic valve and complex aortic-root aneurysm with an aortic-root xenograft. A CentriMag® left ventricular assist device was implanted for cardiac support and was subsequently replaced with a HeartMate II® left ventricular assist device. A day later, the patient was returned to the operating room for control of bleeding, and thrombotic occlusion of the prosthetic aortic valve was detected. The patient underwent thrombus removal, oversewing of the prosthetic valve, and bypass of the left anterior descending coronary artery. This case emphasizes the hazard of bypassing a failed left ventricle with a cardiac assist device after aortic valve replacement, even with a bioprosthesis.

Gene-expression profiling for rejection surveillance after cardiac transplantation

BACKGROUND

Endomyocardial biopsy is the standard method of monitoring for rejection in recipients of a cardiac transplant. However, this procedure is uncomfortable, and there are risks associated with it. Gene-expression profiling of peripheral-blood specimens has been shown to correlate with the results of an endomyocardial biopsy.

METHODS

We randomly assigned 602 patients who had undergone cardiac transplantation 6 months to 5 years previously to be monitored for rejection with the use of gene-expression profiling or with the use of routine endomyocardial biopsies, in addition to clinical and echocardiographic assessment of graft function. We performed a noninferiority comparison of the two approaches with respect to the composite primary outcome of rejection with hemodynamic compromise, graft dysfunction due to other causes, death, or retransplantation.

RESULTS

During a median follow-up period of 19 months, patients who were monitored with gene-expression profiling and those who underwent routine biopsies had similar 2-year cumulative rates of the composite primary outcome (14.5% and 15.3%, respectively; hazard ratio with gene-expression profiling, 1.04; 95% confidence interval, 0.67 to 1.68). The 2-year rates of death from any cause were also similar in the two groups (6.3% and 5.5%, respectively; P=0.82). Patients who were monitored with the use of gene-expression profiling underwent fewer biopsies per person-year of follow-up than did patients who were monitored with the use of endomyocardial biopsies (0.5 vs. 3.0, P<0.001).

CONCLUSIONS

Among selected patients who had received a cardiac transplant more than 6 months previously and who were at a low risk for rejection, a strategy of monitoring for rejection that involved gene-expression profiling, as compared with routine biopsies, was not associated with an increased risk of serious adverse outcomes and resulted in the performance of significantly fewer biopsies. (ClinicalTrials.gov number, NCT00351559.)

Extended mechanical circulatory support with a continuous-flow rotary left ventricular assist device

OBJECTIVES

This study sought to evaluate the use of a continuous-flow rotary left ventricular assist device (LVAD) as a bridge to heart transplantation.

BACKGROUND

LVAD therapy is an established treatment modality for patients with advanced heart failure. Pulsatile LVADs have limitations in design precluding their use for extended support. Continuous-flow rotary LVADs represent an innovative design with potential for small size and greater reliability by simplification of the pumping mechanism.

METHODS

In a prospective, multicenter study, 281 patients urgently listed (United Network of Organ Sharing status 1A or 1B) for heart transplantation underwent implantation of a continuous-flow LVAD. Survival and transplantation rates were assessed at 18 months. Patients were assessed for adverse events throughout the study and for quality of life, functional status, and organ function for 6 months.

RESULTS

Of 281 patients, 222 (79%) underwent transplantation, LVAD removal for cardiac recovery, or had ongoing LVAD support at 18-month follow-up. Actuarial survival on support was 72% (95% confidence interval: 65% to 79%) at 18 months. At 6 months, there were significant improvements in functional status and 6-min walk test (from 0% to 83% of patients in New York Heart Association functional class I or II and from 13% to 89% of patients completing a 6-min walk test) and in quality of life (mean values improved 41% with Minnesota Living With Heart Failure and 75% with Kansas City Cardiomyopathy questionnaires). Major adverse events included bleeding, stroke, right heart failure, and percutaneous lead infection. Pump thrombosis occurred in 4 patients.

CONCLUSIONS

A continuous-flow LVAD provides effective hemodynamic support for at least 18 months in patients awaiting transplantation, with improved functional status and quality of life. (Thoratec HeartMate II Left Ventricular Assist System [LVAS] for Bridge to Cardiac Transplantation; NCT00121472).

Recognition and management of complex rhythm disorders in heterotopic heart transplantation

Managing arrhythmias is challenging in patients who have undergone heterotopic heart transplantation because of the superimposed rhythms of the native and donor hearts. We present the case of a 43-year-old man with a previously placed biventricular pacemaker who underwent heterotopic heart transplantation and later developed acute rejection of the donor heart, which led to bradycardia and pause-dependent ventricular fibrillation. The patient remained clinically stable in the short term, likely because of partial recovery of myocardial function in the native heart. He later underwent placement of a pacing lead in the donor heart, allowing linking of the two hearts via a biventricular pacemaker.

Devices in heart failure: potential methods for device-based monitoring of congestive heart failure

Congestive heart failure has long been one of the most serious medical conditions in the United States; in fact, in the United States alone, heart failure accounts for 6.5 million days of hospitalization each year. One important goal of heart-failure therapy is to inhibit the progression of congestive heart failure through pharmacologic and device-based therapies. Therefore, there have been efforts to develop device-based therapies aimed at improving cardiac reserve and optimizing pump function to meet metabolic requirements. The course of congestive heart failure is often worsened by other conditions, including new-onset arrhythmias, ischemia and infarction, valvulopathy, decompensation, end-organ damage, and therapeutic refractoriness, that have an impact on outcomes. The onset of such conditions is sometimes heralded by subtle pathophysiologic changes, and the timely identification of these changes may promote the use of preventive measures. Consequently, device-based methods could in the future have an important role in the timely identification of the subtle pathophysiologic changes associated with congestive heart failure.

The effect of etanercept on cardiac transplant recipients: a study of TNFalpha antagonism and cardiac allograft hypertrophy

Cardiac allograft hypertrophy is associated with persistent expression of cardiac tumor necrosis factor (TNF)-alpha. We investigated whether TNFalpha antagonism would impact allograft hypertrophy. EFECT (EFfect of Etanercept on Cardiac Transplantation) was a randomized, controlled, double-blind trial evaluating the effect of etanercept versus placebo treatment immediately posttransplant. The primary end-point was change in left ventricular (LV) mass after 6 months. Secondary endpoints included degree of collagen deposition at 6 months and incidence of adverse events. Forty-nine patients were randomized to either etanercept or placebo. LV mass increased significantly in both arms at 6 months, with a smaller increase in the etanercept group (19% vs. 33%, P=ns). Myocardial collagen content increased in the placebo, but not the etanercept, group (+39.8%, P<0.08 vs. -7.0%, P=NS). Allograft hypertrophy develops posttransplant with a corresponding increase in extracellular matrix. Etanercept appeared to decrease LV hypertrophy by decreasing extracellular matrix deposition.

Hypertrophy, increased ejection fraction, and reduced Na-K-ATPase activity in phospholemman-deficient mice

Phospholemman (FXYD1), a 72-amino acid transmembrane protein abundantly expressed in the heart and skeletal muscle, is a major substrate for phosphorylation in the cardiomyocyte sarcolemma. Biochemical, cellular, and electrophysiological studies have suggested a number of possible roles for this protein, including ion channel modulator, taurine-release channel, Na(+)/Ca(2+) exchanger modulator, and Na-K-ATPase-associated subunit. We have generated a phospholemman-deficient mouse. The adult null mice exhibited increased cardiac mass, larger cardiomyocytes, and ejection fractions that were 9% higher by magnetic resonance imaging compared with wild-type animals. Notably, this occurred in the absence of hypertension. Total Na-K-ATPase activity was 50% lower in the phospholemman-deficient hearts. Expression (per unit of membrane protein) of total Na-K-ATPase was only slightly diminished, but expression of the minor alpha(2)-isoform, which has been specifically implicated in the control of contractility, was reduced by 60%. The absence of phospholemman thus results in a complex response, including a surprisingly large reduction in intrinsic Na-K-ATPase activity, changes in Na-K-ATPase isoform expression, increase in ejection fraction, and increase in cardiac mass. We hypothesize that a primary effect of phospholemman is to modulate the Na-K-ATPase and that its reduced activity initiates compensatory responses.

Gene structure and expression of phospholemman in mouse

Phospholemman (PLM) is a small transmembrane cardiac protein that is the major sarcolemmal substrate for phosphorylation in response to adrenergic stimulation. PLM likely plays a role in muscle contractility and cell volume regulation through its function as a channel or a channel regulator. We are the first to describe the structure of the PLM gene and to demonstrate PLM cDNA splice variants. We cloned the murine PLM cDNA and used it as a probe to isolate the gene from a 129/SvJ genomic library. The gene contains seven introns and eight exons. The coding sequence is interrupted by five introns; the 5' untranslated region by two. Using rapid amplification of 5' cDNA ends we identified transcription start sites and four splice variants of the 5' untranslated domain. There was no TATA box or CAAT box in the putative promoter regions. The gene has several stretches of dinucleotide repeats. The 3' untranslated domains of mouse PLM cDNA clones show sequence differences not accounted for by alternative splicing. Mouse PLM shares 93, 83 and 80% amino acid identity with rat, dog, and human PLMs, respectively. Tissue expression of murine PLM parallels that in other species, being highest in heart, skeletal muscle, and liver.