Genetic Counseling and Screening Issues in Familial Dilated Cardiomyopathy

Idiopathic dilated cardiomyopathy (IDC), a treatable condition characterized by left ventricular dilatation and systolic dysfunction of unknown cause, has only recently been recognized to have genetic etiologies. Although familial dilated cardiomyopathy (FDC) was thought to be infrequent, it is now believed that 30-50% of cases of IDC may be familial. Echocardiographic and electrocardiographic (ECG) screening of first-degree relatives of individuals with IDC and FDC is indicated because detection and treatment are possible prior to the onset of advanced, symptomatic disease. However, such screening often creates uncertainty and anxiety surrounding the significance of the results. Furthermore, FDC demonstrates incomplete penetrance, variable expression, and significant locus and allelic heterogeneity, making genetic counseling complex. The provision of genetic counseling for IDC and FDC will require collaboration between cardiologists and genetics professionals, and may also improve the recognition of FDC, the availability of support services, and overall outcomes for patients and families.

Novel lamin A/C mutations in two families with dilated cardiomyopathy and conduction system disease

BACKGROUND

The LMNA gene, one of 6 autosomal disease genes implicated in familial dilated cardiomyopathy, encodes lamins A and C, alternatively spliced nuclear envelope proteins. Mutations in lamin A/C cause 4 diseases: Emery-Dreifuss muscular dystrophy, limb girdle muscular dystrophy type 1B, Dunnigan-type familial partial lipodystrophy, and dilated cardiomyopathy.

METHODS AND RESULTS

Two 4-generation white families with autosomal dominant familial dilated cardiomyopathy and conduction system disease were found to have novel mutations in the rod segment of lamin A/C. In family A a missense mutation (nucleotide G607A, amino acid E203K) was identified in 14 adult subjects; disease was manifest as progressive conduction disease in the fourth and fifth decades. Death was caused by heart failure. In family B a nonsense mutation (nucleotide C673T, amino acid R225X) was identified in 10 adult subjects; disease was also manifest as progressive conduction disease but with earlier onset (third and fourth decades), ventricular dysrhythmias, left ventricular enlargement, and systolic dysfunction. Death was caused by heart failure and sudden cardiac death. Skeletal muscle disease was not observed in either family.

CONCLUSIONS

Novel rod segment mutations in lamin A/C cause variable conduction system disease and dilated cardiomyopathy without skeletal myopathy.

Distribution and declines in cardiac allograft radionuclide left ventricular ejection fractions in relation to late mortality

BACKGROUND

Cardiac allograft left ventricular ejection fraction (LVEF) is an important measure of left ventricular systolic function. Despite widespread use of LVEF after transplantation, its normal range and prognostic value in cardiac allografts has not been defined.

METHODS

We conducted a retrospective cohort study among 292 consecutive adult heart transplant patients. Left ventricular ejection fractions were performed at 1, 3, 12, 24, and 48 months after transplantation using radionuclide ventriculography. Endomyocardial biopsies assessed rejection, right heart catheterization assessed loading conditions, and angiography assessed allograft coronary artery disease. We used Cox proportional hazards model to examine the predictive value of LVEF on late mortality.

RESULTS

Of the patients who survived > or =4 years, the mean allograft LVEF decreased 4.7 units at 3 months, from 63.8 to 59.7; an additional 4.1 units at 12 months, from 59.7 to 55.6 (p < 0.001); and remained stable afterward. These changes were not associated with concurrent changes in loading conditions, episodes of rejection, or development of allograft coronary artery disease. Left ventricular ejection fraction lower than the 95% normal limit (<40%) at 12 months was inversely associated with risk for late cardiac mortality (relative risk = 3.5, 95% confidence interval = 1.0-12.2), while controlling for recipient age, sex, donor age, and rejection episodes.

CONCLUSIONS

The cardiac-allograft LVEF frequently decreases in the first year after transplantation. The 95th percentile of allograft LVEF value (<40%) at Year 1 predicts late cardiac mortality among transplant recipients.

Prospective evaluation of an outpatient heart failure management program

BACKGROUND

Although considerable effort has been devoted to the follow-up of hospitalized patients, the effectiveness and process of heart failure outpatient management have not been well demonstrated.

METHODS AND RESULTS

All new patients referred to the program from April 1997 to September 1998 were followed and managed by comprehensive strategies including preemptive hospitalization. Quality of life (QOL) and patients' self-care adherence behaviors were measured at baseline, 3 months, and 6 months. Clinical outcomes were compared for the 6 months before and 6 months after referral. A total of 108 patients were recruited. Patients' self-care knowledge score was improved over time (difference score = 0.9, P <.01). The proportion of patients weighing themselves daily increased by 24% (P =.02). The proportion of patients with New York Heart Association (NYHA) class III to IV was 67.6% at baseline and 49.1% at 6 months (P =.01). Compared with 6 months before referral, the program intervention was accompanied by a 52% reduction in the risk of hospitalization for cardiovascular causes (56.1% v 27.2%, P <.001) and a 72% reduction in emergency room visits (53.6% v 14.5%, P <.01). The total hospital admissions for cardiovascular causes decreased by 59% from 94 to 39; the total emergency room visits decreased by 77% from 83 to 19. The patients' QOL was improved over time with a change score of 11.2 (P <.001) at 3 months and 10.7 (P <.001) at 6 months.

CONCLUSION

Our study shows the effectiveness of this heart failure outpatient management program.

Comparative responsiveness of Short-Form 12 and Minnesota Living With Heart Failure Questionnaire in patients with heart failure

BACKGROUND

The Short-Form 12 (SF-12) and Living With Heart Failure Questionnaire (LHFQ) are commonly used to measure quality of life (QOL) in heart failure outcomes research. Their comparative responsiveness, however, has not been documented.

METHODS AND RESULTS

A prospective cohort study was conducted among patients attending a university-based heart failure clinic between April 1997 and September 1998. All patients received comprehensive heart failure care management. QOL of patients was assessed by the SF-12 and LHFQ at baseline and 3 months. Of 87 patients completing follow-up, the mean change score was 10.1 for the LHFQ and 5.8 for the SF-12 (both Ps < .001). The change scores of the instruments were correlated (r = 0.61; P < .001). The SF-12 had a greater ability than the LHFQ to statistically detect change in physical health but was less sensitive to changes in mental health. The LHFQ performed better than the SF-12 in the ability to distinguish the differences in perceived global health transition.

CONCLUSION

The LHFQ is more responsive than the SF-12 to changes in QOL. The SF-12 should not be used alone to measure the changes in QOL of patients with heart failure.

Familial dilated cardiomyopathy: echocardiographic diagnostic criteria for classification of family members as affected

BACKGROUND

Echocardiographic criteria for left ventricular enlargement (LVE) used to classify subjects as affected in families with familial dilated cardiomyopathy (FDC) have been inconsistent. A recent report from a large Framingham echocardiographic study provides an opportunity to improve the assignment of LVE and FDC in kindreds, principally with a dilated phenotype. The objective of this study is to evaluate an alternative diagnostic criteria for FDC based only on LVE with no measure of fractional shortening (FS).

METHODS AND RESULTS

We compared our proposed criteria for LVE and FDC with previous approaches by applying them to 166 adults derived from three large FDC pedigrees. Our proposed FDC diagnostic criteria are a sex- and height-specific method based only on LVE, without regard for FS, set as a 97.5% upper limit for left ventricular end-diastolic dimension (LVEDD) from the Framingham study. Other methods used to assign LVE were (1) a 95% upper limit for LVEDD by the Framingham study; (2) the method of Henry et al. (1980) based on age and body surface area (BSA); and (3) the National Heart, Lung, and Blood Institute (NHLBI) method with a cut point of LVEDD greater than 2.7 cm/BSA. Three other commonly used diagnostic criteria for FDC were based on various LVE standards combined with an FS of 27% to 30%. For LVE, the Framingham-97.5% was the most stringent (21 of 134 subjects identified; 15.7%), the NHLBI standard the least stringent (57 of 161 subjects identified; 35.4%), and the Henry-112% method intermediate (44 of 161 subjects identified; 27.3%). More women were identified with the Framingham method (57.1%) versus the Henry-112% (40.9%). The Henry-112% and NHLBI methods identified 11.4% and 7.0% of subjects with body mass indices (BMIs) of 35 or greater, respectively. For FDC, our proposed FDC diagnostic criteria identified similar numbers of subjects (21 subjects) as the three other criteria (range, 22 to 27 subjects), but inconsistency was noted (54.2% to 66.7%), with kappa values from 0.49 to 0.55 resulting from different sensitivities to sex, LVE, FS, and BMI.

CONCLUSION

Our proposed FDC diagnostic criteria are stringent to assign FDC family members as affected compared with other commonly used criteria. The use of LVEDD alone may be preferable for FDC family screening, although further validation of this approach with phenotypic and genotypic data from other large FDC pedigrees is needed.

Clinical profiles of four large pedigrees with familial dilated cardiomyopathy: preliminary recommendations for clinical practice

OBJECTIVES

This study aimed to characterize the clinical profile of familial dilated cardiomyopathy (FDC) in the families of four index patients initially diagnosed with idiopathic dilated cardiomyopathy (IDC) and to provide clinical practice recommendations for physicians dealing with these diseases.

BACKGROUND

Recent evidence indicates that approximately one-half of patients diagnosed with IDC will have FDC, a genetically transmissible disease, but the clinical profile of families screened for FDC in the U.S. has not been well documented. Additionally, recent ethical guidelines suggest increased responsibilities in caring for patients with newly found genetic cardiovascular disease.

METHODS

After identification of four families with FDC, we undertook clinical screening including medical history, physical examination, electrocardiogram and echocardiogram. Diagnostic criteria for FDC-affected status of asymptomatic family members was based on left ventricular enlargement (LVE). Subjects with confounding cardiovascular diagnoses or body mass indices >35 were excluded.

RESULTS

We identified 798 living members from the four FDC pedigrees, and screened 216 adults and 129 children (age <16 years). Twenty percent of family members were found to be affected with FDC; 82.8% of those affected were asymptomatic. All four pedigrees demonstrated autosomal dominant patterns of inheritance. The average left ventricular end-diastolic dimension was 61.4 mm for affected and 48.4 mm for unaffected subjects, with an average age of 38.3 years (+/- 14.6 years) for affected and 32.1 years for unaffected subjects. The age of onset for FDC varied considerably between and within families. Presenting symptoms when present were decompensated heart failure or sudden death.

CONCLUSIONS

We propose that with a new diagnosis of IDC, a thorough family history for FDC should be obtained, followed by echocardiographic-based screening of first-degree relatives for LVE, assuming their voluntary participation. If a diagnosis of FDC is established, we suggest further screening of first-degree relatives, and all subjects with FDC undergo medical treatment following established guidelines. Counseling of family members should emphasize the heritable nature of the disease, the age-dependent penetrance and the unpredictable clinical course.

Was the decreasing trend in hospital mortality from heart failure attributable to improved hospital care? The Oregon experience, 1991-1995

OBJECTIVE

To assess the trend in risk-adjusted hospital mortality from heart failure.

STUDY DESIGN

Oregon hospital discharge data from 1991 through 1995 were analyzed.

PATIENTS AND METHODS

A total of 29,530 hospitalizations because of heart failure in elderly patients (age > or = 65 years) were identified from International Classification of Diseases, 9th Revision, codes 428.0-428.9. The logistic regression and life table analyses were used to assess the risk-adjusted trend in hospital mortality from heart failure.

RESULTS

From 1991 through 1995, 1757 (5.9%) patients with heart failure died in the hospital; 920 (52.4%) of them died within 3 days. The percentage of patients discharged to skilled nursing facilities increased from 6.1% in 1991 to 9.8% in 1995 (P value for trend < .001), whereas the percentage of patients discharged directly to home decreased from 69.2% in 1991 to 62.4% in 1995 (P value for trend < .001). The mean length of stay decreased from 5.15 days in 1991 to 3.97 days in 1995. The age- and sex-standardized mortality rate decreased by 33.8% from 7.4 in 1991 to 4.8 in 1995 (P value for trend < .01). Additional adjustment for comorbidity using multiple logistic regression revealed a greater reduction of 41.0% in the mortality rate (odds ratio = 0.59; 95% confidence interval = 0.50, 0.69) and a reduction of 46.0% in the 3-day mortality rate (odds ratio = 0.54; 95% confidence interval = 0.43, 0.67) across the 5-year period. Life table analysis showed consistently lower cumulative mortality rates during the first week after admission in 1995 compared with those in 1991 (P < .001).

CONCLUSION

There was a decreasing trend over time in the risk-adjusted hospital mortality rates from heart failure, which was not an artifact of decreasing length of stay. Our findings raised the possibility of improved hospital care for heart failure in Oregon.

Extracellular signal-regulated protein kinase activation is required for the anti-hypertrophic effect of atrial natriuretic factor in neonatal rat ventricular myocytes

Atrial natriuretic factor (ANF) inhibits proliferation in non-myocardial cells and is thought to be anti-hypertrophic in cardiomyocytes. We investigated the possibility that the anti-hypertrophic actions of ANF involved the mitogen-activated protein kinase signal transduction cascade. Cultured neonatal rat ventricular myocytes treated for 48 h with the alpha(1)-adrenergic agonist phenylephrine (PE) had an 80% increase in cross-sectional area (CSA). ANF alone had no effect but inhibited PE-induced increases in CSA by approximately 50%. The mitogen-activated protein kinase/ERK kinase (MEK) inhibitor PD098059 minimally inhibited PE-induced increases in CSA, but it completely abolished ANF-induced inhibition of PE-induced increases. ANF-induced extracellular signal-regulated protein kinase (ERK) nuclear translocation was also eliminated by PD098059. ANF treatment caused MEK phosphorylation and activation but failed to activate any of the Raf isoforms. ANF induced a rapid increase in ERK phosphorylation and in vitro kinase activity. PE also increased ERK activity, and the combined effect of ANF and PE appeared to be additive. ANF-induced ERK phosphorylation was eliminated by PD098059. ANF induced minimal phosphorylation of JNK or p38, indicating that its effect on ERK was specific. ANF-induced activation of ERK was mimicked by cGMP analogs, suggesting that ANF-induced ERK activation involves the guanylyl cyclase activity of the ANF receptor. These data suggest that there is an important linkage between cGMP signaling and the mitogen-activated protein kinase cascade and that selective ANF activation of ERK is required for the anti-hypertrophic action of ANF. Thus, ANF expression might function as the natural defense of the heart against maladaptive hypertrophy through its ability to activate ERK.

Factors influencing knowledge of and adherence to self-care among patients with heart failure

BACKGROUND

Patient education has been shown to be a key component in comprehensive heart failure management. Few data, however, are available regarding patients' knowledge of and adherence to self-care recommendations for the disease.

OBJECTIVES

To assess the knowledge level of and adherence to self-care among patients with heart failure and to determine associated factors.

METHODS

We conducted a needs-assessment survey among new patients visiting a heart failure clinic from April 1997 through June 1998. Multiple linear regression analysis was used to assess the factors predictive of patients' knowledge level and adherence behaviors.

RESULTS

Of the 113 patients surveyed, 77% were referred by cardiologists and 60% had New York Heart Association class III or IV status. Two thirds of the patients reported receiving information or advice about self-care from health care providers. When asked how much they knew about congestive heart failure, however, 37% said "a little or nothing," 49% said "some," and only 14% said "a lot." Approximately 40% of the patients did not recognize the importance of weighing themselves daily and 27% weighed themselves twice a month or less often. Although 80% of the patients knew they should limit their salt intake, only one third always avoided salty foods. Additionally, 25% of the patients did not appreciate the risk of alcohol use and 36% believed they should drink a lot of fluids. The multiple linear regression analysis indicated that a higher knowledge score was associated with being married, prior hospitalization, and having received both advice and information about self-care from physicians or nurses. A poor adherence behavior score was associated with being unmarried, lower perceived self-efficacy, a lack of knowledge about self-care, and no prior hospitalization.

CONCLUSIONS

We observed a gap between patients receiving and absorbing or retaining information on self-care for congestive heart failure supplied by health care providers. Self-care education needs to be directed to outpatients in addition to inpatients.

Analysis of trends in hospitalizations for heart failure

BACKGROUND

Over the past 10 years, efforts have been made to control the cost of care for patients with congestive heart failure (CHF) through reducing hospitalizations and shortening lengths of stay. Few data are available regarding the effectiveness of these intervention strategies on a community basis.

METHODS AND RESULTS

We analyzed the Oregon hospital discharge database. Multivariable methods were used to assess trends while controlling for confounding factors, such as age, sex, and comorbidity. The hospital admission rates for CHF were stable over time in all age groups. The age- and sex-standardized admission rate among people aged 65 years or older decreased slightly from 13.9/1,000 in 1991 to 12.9/1,000 in 1995. The annual hospital readmission rate remained constant over time, with an average rate of 15.3%. The average length of hospital stay decreased from 5.01 days in 1991 to 3.95 days in 1995. The in-hospital mortality rate decreased from 6.9% in 1991 to 4.7% in 1995, independent of length of stay.

CONCLUSION

We observed stable hospital admission and readmission rates for CHF, accompanied by a decreasing trend in the length of hospital stay and in-hospital mortality. Our findings raise the possibility of improved care management for heart failure over time.

Managed care and outcomes of hospitalization among elderly patients with congestive heart failure

BACKGROUND

Little was known about the impact of the health maintenance organization-managed care on patients hospitalized for congestive heart failure. Understanding this issue is important with regards to the increasing prevalence of congestive heart failure among the elderly population as well as the growing enrollment of Medicare beneficiaries in managed care.

OBJECTIVE

To examine the impact of the health maintenance organization-managed care on the outcomes of hospitalization among patients with congestive heart failure.

PATIENTS AND METHODS

We analyzed the Oregon hospital discharge data set. Study subjects were all patients with congestive heart failure aged 65 years or older (N=5821) discharged from hospitals in 1995 and classified into 6 insurance groups: managed care, Medicare, Medicaid, commercial or private insurance, self-pay, and other.

RESULTS

The percentage of patients admitted to hospitals via emergency departments was significantly higher in the managed care patients (69%) than in other health insurance coverage groups (29.0%-58.5%; P<.001). After adjusting for age, sex, and comorbidity, the managed care patients experienced a similar length of hospital stay (3.6 days) as the commercial or private insurance patients (3.7 days; P = .67), but a shorter length of hospital stay than the Medicare patients (4.0 days; P<.001), self-pay patients (4.5 days; P<.001), and other patients (4.8 days; P<.001). No difference in the in-hospital mortality rate was seen among the insurance groups (P = .37). The readmission rate was slightly higher in managed care patients (9.1%) than in commercial insurance patients (6.8%) and Medicare patients (7.5%). The differences, however, were not statistically significant after adjusting for the confounding factors (P = .59).

CONCLUSIONS

Our results suggest no association between managed care and poor short-term outcomes of hospitalization in patients with congestive heart failure. Attention, however, needs to be paid to the increased use of emergency departments by managed care patients.

Clinical outcomes, quality of life, and cost outcomes after cardiac transplantation

Cardiac transplantation improves survival in patients with advanced heart failure, especially those who are dependent on intravenous inotropic support or mechanical assistance. However, cardiac transplantation remains a treatment modality rather than a curative procedure, and thus, necessitates long-term care and indefinite immunosuppression. Although quality of life is improved for most cardiac transplant recipients, concerted effort is necessary for long-term care and follow-up of the transplanted heart. The economics of cardiac transplantation are receiving increased scrutiny, especially because of the increasing pretransplant hospital expenditures that have resulted from transplantation in more patients in the hospital who require intravenous inotropic support or mechanical devices. This shift ultimately is related to the reduced supply of donors relative to the demand. The ultimate impact of managed care on cardiac transplantation is not clear, but it probably will continue to reduce expenditures in the near term.

Carvedilol produces dose-related improvements in left ventricular function and survival in subjects with chronic heart failure. MOCHA Investigators

BACKGROUND

We conducted a multicenter, placebo-controlled trial designed to establish the efficacy and safety of carvedilol, a "third-generation" beta -blocking agent with vasodilator properties, in chronic heart failure.

METHODS AND RESULTS

Three hundred forty-five subjects with mild to moderate, stable chronic heart failure were randomized to receive treatment with placebo, 6.25 mg BID carvedilol (low-dose group), 12.5 mg BID carvedilol (medium-dose group), or 25 mg BID carvedilol (high-dose group). After a 2- to 4-week up-titration period, subjects remained on study medication for a period of 6 months. The primary efficacy parameter was submaximal exercise measured by two different techniques, the 6-minute corridor walk test and the 9-minute self-powered treadmill test. Carvedilol had no detectable effect on submaximal exercise as measured by either technique. However, carvedilol was associated with dose-related improvements in LV function (by 5, 6, and 8 ejection fraction [EF] units in the low-, medium-, and high-dose carvedilol groups, respectively, compared with 2 EF units with placebo, P < .001 for linear dose response) and survival (respective crude mortality rates of 6.0%, 6.7%, and 1.1% with increasing doses of carvedilol compared with 15.5% in the placebo group, P < .001). When the three carvedilol groups were combined, the all-cause actuarial mortality risk was lowered by 73% in carvedilol-treated subjects (P < .001). Carvedilol also lowered the hospitalization rate (by 58% to 64%, P = .01) and was generally well tolerated.

CONCLUSIONS

In subjects with mild to moderate heart failure from systolic dysfunction, carvedilol produced dose-related improvements in LV function and dose-related reductions in mortality and hospitalization rate.

Pharmacologic and hemodynamic effects of combined beta-agonist stimulation and phosphodiesterase inhibition in the failing human heart

STUDY OBJECTIVES

We measured the individual and combined effects of the beta-agonist dobutamine and the phosphodiesterase inhibitor enoximone both in vitro and in vivo in the failing human heart.

DESIGN

This was an unblinded, prospective study.

SETTING AND PATIENTS

The in vitro measurements were performed on 20 hearts obtained from subjects with end-stage biventricular failure and from seven normal hearts. The in vivo measurements were performed in eight subjects with class IV heart failure.

INTERVENTIONS AND MEASUREMENTS

The in vitro measurements of enoximone, dobutamine, and the combination of these agents were phosphodiesterase activity using a sarcoplasmic reticulum-enriched preparation, cyclic adenosine monophosphate (cAMP) accumulation using particulate fractions, and tension response using isolated right ventricular trabeculae. The dose response to dobutamine, the combination of enoximone and dobutamine, and the combination of nitroprusside and dobutamine were measured in vivo using invasive hemodynamic monitoring.

RESULTS

In vitro, enoximone exhibited dose-dependent inhibition of phosphodiesterase activity. The addition of enoximone to dobutamine resulted in an upward and leftward shift of the dobutamine dose-response curve for both cAMP production and contractile response. In vivo, enoximone significantly shifted the dobutamine dose-response curves for cardiac index, left ventricular stroke work index, and heart rate upward and to the left; and shifted the dobutamine dose-response curves for right atrial, pulmonary arterial, and pulmonary wedge pressures downward and to the right.

CONCLUSIONS

Enoximone exerts favorable effects on cardiac performance that are additive to those produced by dobutamine. These effects are mediated by increasing cellular cAMP concentrations through independent, additive mechanisms.

The somatostatin receptor SSTR1 is coupled to phosphotyrosine phosphatase activity in CHO-K1 cells

Somatostatin receptors are abundantly expressed on a variety of human endocrine and epithelial tumors. The ability of these receptors to couple to effector pathways that inhibit the growth of these tumor cells has prompted the use of somatostatin agonists in the treatment of human neoplasms. It has been demonstrated that somatostatin stimulates a phosphotyrosine phosphatase in human tumor cells through a receptor-mediated process. This stimulation may counteract the growth-promoting properties of growth factors and the receptor tyrosine kinases that they activate. The recent cloning and characterization of distinct somatostatin receptor subtypes raise the possibility that different receptor subtypes mediate distinct effector pathways. To determine whether cloned somatostatin receptors could mediate coupling to phosphotyrosine phosphotyrosine phosphatase activity, we examined phosphatase activity after somatotostatin activation of the rat somatostatin receptors SSTR1 and SSTR2 after their stable expression in heterologous Chinese Hamster Ovary (CHO-K1) cells. We found that stimulation of SSTR1 cells was capable of increasing phosphotyrosine phosphatase activity, despite the coupling of both receptors to the inhibition of adenylyl cyclase in these cells. This activation was characterized by an EC50 of 70 nM and was sensitive to pertussis toxin. In addition, we demonstrate that activation of phosphotyrosine phosphatase activity in pituitary cell lines correlates with the endogenous expression of the SSTR1 gene within these cells.

The somatostatin receptors SSTR1 and SSTR2 are coupled to inhibition of adenylyl cyclase in Chinese hamster ovary cells via pertussis toxin-sensitive pathways

Somatostatin exerts multiple effects throughout the body by binding to specific somatostatin receptors. Two classes of somatostatin receptors, SRIF1 and SRIF2, have been distinguished biochemically and pharmacologically. Two cDNAs have been recently isolated that encode somatostatin receptors 1 and 2 (SSTR1 and SSTR2, respectively). The pharmacological characteristics of receptors expressing these cDNAs resemble those of the SRIF2 and SRIF1 classes of somatostatin receptors, respectively. We stably expressed the rat homologs of both receptors in Chinese hamster ovary (CHO) cells (type K1). These transfected cell lines recognized the endogenous ligands SS14 and SS28 with high affinity, whereas the synthetic analog MK678 identified only SSTR2. In preparations of CHO-SSTR1 or CHO-SSTR2 cells, SS14 and SS28 inhibited forskolin-stimulated adenylyl cyclase activity by approximately 35%, with ED50 values in the nanomolar range. The adenylyl cyclase inhibition was dependent upon the guanine nucleotide GTP and could be ablated with pertussis toxin preincubation. The present data indicate that SSTR1 and SSTR2 are coupled to inhibition of adenylyl cyclase via pertussis toxin- sensitive G-proteins.

The specificity of normal qualitative angiography in excluding cardiac allograft vasculopathy

It has been frequently stated that qualitative coronary angiography is insensitive in the diagnosis of cardiac allograft vasculopathy because the disease can be diffuse without observable luminal irregularities. However, the specificity of otherwise normal qualitative coronary angiography for excluding cardiac allograft vasculopathy has not been prospectively studied. Accordingly, 28 patients who underwent transplantation from June 23, 1989 to July 9, 1990 underwent coronary angiography within 3 weeks (predischarge) after transplantation and at 1 year. Twenty-one of these patients who had both normal 1-year qualitative coronary angiography and predischarge angiograms adequate for analysis served as the study cohort. Cross-section luminal diameters (average, 14.3 per angiogram) were measured at the same branch points on each pair of angiograms in the right anterior oblique view. Seventeen of the 21 patients had no change in average luminal diameters, while the remaining four patients had consistent narrowing in all vessels and in all segments. In these four patients, the mean fall in luminal diameter was 20% +/- 2%. The specificity of normal qualitative angiography in predicting absence of cardiac allograft vasculopathy is 81%. In conclusion, qualitative angiography usually predicts the absence of cardiac allograft vasculopathy. However, 15% to 20% of patients will have diffuse disease not detected by a normal study.

Heart transplantation in patients with previous cardiac operations. Excellent clinical results

A significant proportion of potential transplant recipients have undergone previous cardiac procedures and may be subject to an increased risk because of technical and other factors inherent in a reoperation. Between December 1985 and June 1991, 155 orthotopic heart transplantations were carried out in 146 patients. Eighty-five transplantations (54.8%) were carried out as the initial cardiac operation (group I); 61 operations (45.2%) were performed in patients who had previous nontransplant cardiac operations (group II). Preoperative variables including hemodynamic indexes, renal function, and status on the waiting list were similar between these groups; however, group II patients tended to be older than group I patients (51.9 +/- 10.7 versus 47.7 +/- 11.6 years, respectively; p < 0.05) and were more likely to have ischemic heart disease (80.3% versus 34.1%) than were those in group I. Significantly longer cardiopulmonary bypass time (127.6 +/- 44.7 minutes versus 108.2 +/- 18.8 minutes, p < 0.01) and duration of operation (448.1 +/- 120.9 minutes versus 353.2 +/- 85.1 minutes, p < 0.01) was found in group II. Operative mortality in group I was 4.7% and in group II was 6.6% (p > 0.9). Group I actuarial survival at 1 year and 5 years was 87.1% +/- 3.6% and 72.9% +/- 6.2%, respectively. Group II actuarial survival was 85.3% +/- 4.5% and 76.0% +/- 6.6%, respectively, for the same time periods. In spite of the greater technical challenge implied by previous cardiac operations, no significant survival differences occurred between these groups (p > 0.9). However, patients undergoing a second cardiac transplantation (n = 9) were identified as a high-risk subset with operative mortality of 22.8% and 1-year survival of only 33.3% +/- 15.7% (p < 0.0003). Cardiac transplantation in patients who have undergone previous nontransplant cardiac operations can be carried out without compromising immediate or long-term outcome.

ABO-incompatible heart transplantation: a special case for the A2 donor

Limited clinical experience concerning heart transplantation across ABO blood group barriers suggests a high incidence of hyperacute rejection and poor patient outcome. Reported is a case of the short-term survival of an ABO-mismatched cardiac graft without evident adverse immunologic effects. A 41-year-old man with blood type O underwent heart transplantation receiving a blood type A2 donor organ. Cyclosporine-based immunosuppression was augmented with daily plasmapheresis and OKT3 therapy. Circulating anti-A antibodies were reduced quickly and held to a very low level with this regimen. The patient remained hemodynamically stable until retransplantation 4 days later. The explanted heart showed no evidence of cellular infiltrate or antibody deposition. Long-term success with the use of type A2 organs in type O recipients has been shown in select series with other types of solid organ transplants. Although this patient underwent retransplantation early, the lack of rejection phenomena gives evidence that the relatively low antigenicity of the A2 subtype may allow planned heart transplantation across this blood group barrier, either as a bridge or on a permanent basis.

Dopaminergic inhibition of DNA synthesis in pituitary tumor cells is associated with phosphotyrosine phosphatase activity

Dopaminergic D2 receptor agonists, such as bromocriptine, are potent anti-proliferative agents in the treatment of human pituitary adenomas. We have reproduced the anti-proliferative effect of dopamine in an established pituitary cell line stably transfected with the rat D2 dopamine receptor cDNA. We found that dopaminergic inhibition of DNA synthesis parallels the stimulation of a phosphotyrosine phosphatase activity. Both actions are blocked by pertussis toxin and by the phosphotyrosine phosphatase inhibitor, vanadate. We suggest that the anti-proliferative action of dopamine is mediated, at least in part, by the dopaminergic stimulation of a phosphotyrosine phosphatase.

Methotrexate for the treatment of patients with multiple episodes of acute cardiac allograft rejection

Of 142 cardiac allograft recipients who underwent transplantation from December 1985 to January 1991, four women and seven men (mean age, 41 +/- 14 years) required multiple (10.5 +/- 3.3) courses of antirejection treatment over a total follow-up period of 30 +/- 15 months. The underlying heart disease was cardiomyopathy in six patients and coronary disease in five patients. These patients were treated with methotrexate (10 mg/wk for 6 weeks). Rejection treatment before methotrexate therapy included six courses of OKT3, one course of antithymocyte globulin, 33 courses of high-dose steroids, and 45 courses of low-dose steroids for the entire group. The average number of rejection treatments per patient before methotrexate therapy was 8.7 +/- 3.5 treatments or 0.90 +/- 0.51 treatments per month of follow-up. After methotrexate therapy the average number of rejection treatments fell to 1.7 +/- 1.1 treatments or 0.11 +/- 0.08 treatments per month of follow-up (p = 0.0002). Seven patients responded to a single course of methotrexate therapy; three patients required two courses (second course, 20 mg/wk for 6 weeks), and one patient required three courses of methotrexate therapy. The only complication associated with methotrexate therapy was one patient in whom cytomegalovirus interstitial pneumonitis developed while on therapy. Methotrexate was well tolerated and appeared to be effective in halting repeated episodes of rejection in this subset of patients who have had multiple episodes of acute rejection.

Prolonged cytomegalovirus infection with viremia is associated with development of cardiac allograft vasculopathy

Several reports have suggested an association between cytomegalovirus infection and the subsequent development of cardiac allograft vasculopathy. The difficulties in interpreting these studies include the variety of methods used for the diagnosis of cytomegalovirus infection and variable criteria for the diagnosis of cardiac allograft vasculopathy. To determine whether specific aspects of cytomegalovirus infection are risk factors for cardiac allograft vasculopathy, the patient population of the Oregon Cardiac Transplant Program was analyzed for the following variables: cytomegalovirus infection, primary cytomegalovirus infection, and persistent cytomegalovirus infection for 4 or 6 months documented by either blood or urine cultures and persistent cytomegalovirus viremia for 4 months. In the 129 patients available for analysis, there was no higher incidence of cardiac allograft vasculopathy in patients with or without cytomegalovirus infection, nor was there a higher incidence of cardiac allograft vasculopathy in primary cytomegalovirus infection. There was a nonstatistically significant trend toward an increased incidence of cardiac allograft vasculopathy in patients with persistent cytomegalovirus infection as assessed by cultures positive for infection in either blood or urine. There was, however, a significant increase in the incidence of cardiac allograft vasculopathy in patients who had persistent viremia for at least 4 months compared with those without this finding (47% vs 18%, respectively; p = 0.012). In our population persistent cytomegalovirus viremia and presumably long-term exposure of the allograft coronary tree to cytomegalovirus is associated with cardiac allograft vasculopathy.

Recurrence of sarcoidosis in a cardiac allograft: control with augmented corticosteroids

Sarcoidosis of the heart is an unusual but previously reported indication for heart transplantation. It is clear that sarcoidosis is a systemic disease, but in spite of this, recurrence in the cardiac allograft has not been previously noted. The case presented here is that of a 34-year-old male in whom cardiac sarcoidosis recurred in the allograft 6 months after heart transplantation.

Differences in beta-adrenergic neuroeffector mechanisms in ischemic versus idiopathic dilated cardiomyopathy

BACKGROUND

We measured the content and activities of components of the beta-adrenergic receptor-G protein-adenylate cyclase complex and adrenergic neurotransmitter levels in left and right ventricular myocardial preparations derived from 77 end-stage failing human hearts from patients with idiopathic dilated cardiomyopathy (IDC) or ischemic dilated cardiomyopathy (ISCDC).

METHODS AND RESULTS

The results were compared with data obtained in 21 nonfailing hearts removed from organ donors. Compared with ISCDC ventricles, IDC left and right ventricles exhibited a greater degree of total beta- or beta 1-receptor downregulation. In contrast, compared with IDC right ventricles, isolated tissue preparations of ISCDC right ventricles exhibited a greater degree of subsensitivity to the inotropic effect of isoproterenol, indicating a relatively greater degree of functional uncoupling of right ventricular ISCDC beta-receptors from mechanical response. In addition, relative to IDC left ventricles, preparations of ISCDC left ventricle exhibited greater subsensitivity to beta-agonist-mediated adenylate cyclase stimulation, indicating functional uncoupling of left ventricular ISCDC beta-receptors from cyclic AMP generation. The uncoupling of beta-receptors in ISCDC left and right ventricles may have been a result of abnormalities in G protein activation of adenylate cyclase; compared with age- and cardiac function-matched respective left or right IDC ventricles, ISCDC left ventricles exhibited less stimulation of adenylate cyclase by NaF or forskolin but no change in Mn2+ stimulation, whereas ISCDC right ventricles exhibited less stimulation by the nonhydrolyzable guanine nucleotide Gpp (NH)p. Also, IDC right ventricles exhibited a "selective" (not present in IDC left ventricles or ISCDC ventricles) decrease in stimulation of adenylate cyclase by Mn2+. Tissue neurotransmitter levels and pertussis toxin-catalyzed ADP ribosylation were altered to similar extents in IDC and ISCDC:

CONCLUSIONS

These data indicate that potentially important differences exist in the regulatory behavior of components of the beta-adrenergic receptor-G protein-adenylate cyclase complex in IDC versus ISCDC, differences that presumably relate to the distinct pathophysiologies of these two types of heart muscle disease.

Low-dose enoximone in subjects awaiting cardiac transplantation. Clinical results and effects on beta-adrenergic receptors

During a 3-year period we administered enoximone, a phosphodiesterase inhibitor with positive inotropic and vasodilator properties, to 73 pretransplantation patients with end-stage heart failure who exhibited a clinical requirement for additional inotropic support. The clinical course and myocardial beta-adrenergic receptor status in the explanted hearts of these 73 patients was compared with results in 113 concurrently listed pretransplantation patients not requiring additional inotropic support. Only three patients required cessation of enoximone because of adverse effects, all from exacerbation of ventricular arrhythmias. Sixty-six of 73 (90.4%) enoximone-treated patients ultimately underwent cardiac transplantation a mean of 39.2 +/- 6.6 days (range 1 to 221 days) after starting enoximone, whereas seven patients (9.6%) died awaiting cardiac transplantation. The respective 1-, 3-, and 6-month pretransplantation survival rates of patients treated with enoximone calculated from their time on the waiting list for transplantation were 88.0%, 82.5%, and 82.5% compared with 92.1%, 83.8%, and 76.2% in control patients not receiving enoximone (all p = not significant). In 25 patients who received enoximone, ventricular myocardial beta-adrenergic receptors were measured at the time of transplantation and compared with values in failing ventricles from 52 pretransplantation patients not exposed to enoximone. Compared with ventricular myocardium of patients not given enoximone or intravenous beta-adrenergic agonists, total beta-adrenergic receptor (beta 1 plus beta 2) density was not decreased in patients treated with enoximone or enoximone plus intravenous beta-adrenergic agonists, but was decreased by 31% (p less than 0.05) in patients given intravenous beta-adrenergic agonists alone. Additionally, patients treated with enoximone had higher myocardial beta 2-adrenergic receptor densities than respective subgroups treated without (28% higher, p less than 0.01) or with (65% higher, p less than 0.01) intravenous beta-adrenergic agonists. Finally, isoproterenol- or calcium-mediated contractile responses in isolated right ventricular preparations from 14 patients treated with enoximone were similar to values in control patients not exposed to enoximone or intravenous beta-adrenergic agonists, suggesting that enoximone-related beta-adrenergic subsensitivity or damage to the contractile apparatus does not occur.

Late infection in cardiac allograft recipients: profiles, incidence, and outcome

Infection continues to cause substantial morbidity and mortality after heart transplantation. Studies focusing on this problem have concentrated on the early posttransplant period, and it is uncertain to what extent infection continues to add to morbidity later after transplantation. Fifty-four patients surviving at least 1 year after heart transplantation made up the study population in this study, and they were surveyed for infections beyond 1 year. In this group there were 15 infections, an incidence of 0.3 infections per patient or 0.016 infections per patient-months of follow-up. Only nine of these infections necessitated hospitalization; two, however, were fatal. Actuarial risk of all late infections and late infections necessitating hospitalization was 13% and 6%, respectively, at 2 years. As expected, bacterial infections made up the largest group (60%), followed by viral disease (27%). Two patients had pulmonary infections, one with Aspergillus and one with Pneumocystis. These data demonstrate that although rates of infection in heart recipients continue to exceed those in the general population, the rates are considerably lower than those in what is seen early after heart transplantation. Despite this, the more unusual infectious agents associated with immune compromise continue to be present.

Mr 40,000 and Mr 39,000 pertussis toxin substrates are increased in surgically denervated dog ventricular myocardium

To test the general hypothesis that cardiac innervation may participate in myocardial G protein regulation, we examined the effects of complete intrapericardial surgical denervation or sham operation in dogs. In particulate fractions of dog left ventricular (LV) myocardium harvested 28-33 days after denervation or sham operation, Mr 40,000 and Mr 39,000 pertussis toxin-sensitive substrates (G proteins) were increased by 31% (1.31 +/- 0.084 vs 1.00 +/- 0.058 OD, arbitrary units, p less than 0.01) and 40% (1.40 +/- 0.117 vs. 1.000 +/- 0.084 OD, arbitrary units, p less than 0.02), respectively, as compared with sham-operated controls. The Mr 40,000 pertussis toxin-sensitive band comigrated with a pertussis toxin-sensitive substrate in human erythrocyte membranes known to contain an alpha Gi species. In these same preparations basal, GTP and GppNHp stimulated adenylate cyclase activities were decreased in denervated heart by 20, 26, and 19%, respectively, consistent with increased activity of an inhibitory G protein. In contrast, Gs function was not altered, because cyc(-) membranes reconstituted with membrane extracts and fluoride and beta-receptor-stimulated adenylate cyclase activity were not different between groups. Furthermore, adenylate cyclase catalytic subunit function as assessed with forskolin and manganese stimulation was not different between preparations of control and denervated heart. We conclude that in preparations of surgically denervated dog myocardium Mr 40,000 and Mr 39,000 pertussis toxin-sensitive G proteins are increased by 31 and 40%, respectively, and that functional alterations in adenylate cyclase activity exist, consistent with increased inhibitory G-protein function.

A1-adenosine receptor inhibition of adenylate cyclase in failing and nonfailing human ventricular myocardium

BACKGROUND

Receptors that couple via the stimulatory G protein, Gs, to adenylate cyclase and to a positive inotropic response have been extensively investigated in falling human heart. In contrast, much less is known about receptors, such as the A1-adenosine receptor, that couple to adenylate cyclase via the inhibitory G protein, Gi, to give a negative inotropic response. Activation of such Gi-coupled receptors might worsen heart failure. Furthermore, alpha Gi is increased in failing human ventricular myocardium, which may enhance inhibitory receptor coupling to adenylate cyclase.

METHODS AND RESULTS

A1-Adenosine receptor inhibition of adenylate cyclase was examined in crude particulate preparations derived from 12 nonfailing and 12 failing human left ventricles. Experimental conditions were designed for maximal inhibitory responses. Dose-response curves were performed with the selective A1-adenosine receptor agonist R-phenylisopropyl-adenosine (R-PIA). No differences in nonfailing versus failing heart were observed for basal adenylate cyclase activity (49.0 +/- 4.1 versus 45.7 +/- 2.6 pmol cyclic AMP/min/mg), maximal R-PIA-mediated inhibition (31.1 +/- 2.6 versus 30.2 +/- 1.6 pmol cyclic AMP/min/mg), ED50 (R-PIA x 10(-7) 1.28 +/- 0.10 versus 1.36 +/- 0.08), or slope (1.06 +/- 0.06 versus 1.03 +/- 0.10), respectively. Furthermore, fluoride, forskolin, and manganese adenylate cyclase activation were not different in failing heart, which is consistent with no change in the catalytic unit of adenylate cyclase. The inhibitory G protein alpha Gi, as quantitated by pertussis toxin-catalyzed ADP-ribosylation, was increased in failing heart (105.7 +/- 5.8 versus 132.7 +/- 3.4 optical density units, p less than 0.003). Basal adenylate cyclase activity was reduced in failing heart (7.8 +/- 0.8 versus 4.5 +/- 0.4 pmol cyclic AMP/min/mg, p less than 0.005) with assay conditions designed to assess G protein effects.

CONCLUSIONS

The A1-adenosine receptor pathway exerts a major inhibitory effect on human myocardial adenylate cyclase activity. Although alpha Gi was increased in failing heart, A1-adenosine receptor inhibition of adenylate cyclase was not altered in preparations of failing versus nonfailing human ventricular myocardium.

Beta-adrenergic pathways in nonfailing and failing human ventricular myocardium

beta-Adrenergic pathways in the human ventricular myocardium mediate the powerful positive inotropic effects of released neurotransmitters (norepinephrine) and circulating hormones (epinephrine) and the response to therapeutically administered beta-agonists. Two genetically and pharmacologically distinct receptors, beta 1 and beta 2, mediate the contractile effects of catecholamines in a similar manner. The biologic signal produced by the occupancy of beta-adrenergic receptors by catecholamine agonists is transduced, amplified, and regulated by a family of guanine nucleotide-binding proteins (G proteins), which serve both stimulatory and inhibitory functions. Although the major biochemical effector of beta-adrenergic receptors is the enzyme protein--coupled directly to ion channels that regulate inotropic and electrophysiological effects. In human ventricular myocardium, heart failure produces changes in the beta-adrenergic receptor pathways that have the collective effect of reducing the degree of inotropic stimulation that may be produced by a given amount of beta-agonist. These changes include downregulation of beta 1-adrenergic receptors, uncoupling of beta 2-adrenergic receptors, and an increase in the functional activity of the inhibitory G protein. These effects in turn are probably caused by exposure to increased amounts of neurotransmitter resulting from a complex series of changes in the cardiac sympathetic nervous system. Finally, the components of the beta-receptor-G protein system may be both acutely and chronically modulated by certain kinds of pharmacological therapy. These observations underscore the importance of the adrenergic nervous system in heart failure, and they create the potential for the development of new interventional strategies designed to alter the natural history of heart muscle disease and heart failure.

Mechanism of action of bucindolol in human ventricular myocardium

The mechanism of action of the beta-receptor antagonist bucindolol was examined in human ventricular myocardium. Bucindolol was found to be a high-affinity competitive beta-blocking agent as determined by bucindolol-[125I]iodocyanopindolol (ICYP) competition curves (KI = 3.7 +/- 1.3 x 10(-9) M, n = 10). This value was in general agreement with bucindolol KB's, determined by antagonism of isoproterenol-stimulated adenylate cyclase activity (KB = 2.8 +/- 0.55 x 10(-9) M, n = 5) or isoproterenol-augmented contraction of right ventricular trabeculae (KB = 2.9 +/- 1.9 x 10(-9) M, n = 3). In contrast, the alpha 1-receptor KI, determined at bucindolol-125IBE2254 (IBE) competition binding in rat cardiac membranes, was 1.2 x 10(-7) M. Bucindolol exhibited no beta 1- or beta 2-receptor subtype selectivity as deduced from blockade of the beta-agonist-coupled adenylate cyclase system, receptor-binding studies with preparations of human ventricular myocardium with predominantly beta 1 or beta 2 receptors, or receptor-binding studies in model systems consisting of beta 1 (guinea pig myocardial membranes) or beta 2 receptors (human mononuclear and frog myocardial membranes). In membranes derived from human ventricular myocardium and human lymphocytes, bucindolol recognized a high-affinity agonist-binding site as determined by guanine nucleotide modulation of competition-binding curves. Although bucindolol has measurable intrinsic sympathomimetic activity (ISA) in some animal systems, no increase in adenylate cyclase activity or muscle contraction was detected in preparations of human heart. In conclusion, bucindolol is a high-affinity nonselective beta-receptor antagonist with no evidence of intrinsic sympathomimetic activity in human ventricular myocardium.

Neurotransmitter depletion compromises the ability of indirect-acting amines to provide inotropic support in the failing human heart

To test the hypothesis that cardiac norepinephrine depletion related to heart failure alters contractile responses to beta-adrenergic agonists with a component of "indirect" action (acting by release of neuronal norepinephrine), we examined the inotropic potential of several pharmacologically distinct beta-agonists. Contractile responses to the nonselective beta-agonist isoproterenol, the beta 2-selective agonist zinterol, and the direct- and indirect-acting agonists dopamine and dopexamine were compared in isolated right ventricular trabeculae removed from failing, nonfailing innervated, and previously transplanted and, therefore, denervated nonfailing human hearts. In failing hearts, the contractile response to isoproterenol was significantly lower (41%) than that in nonfailing innervated hearts. The responses to the mixed agonists dopamine and dopexamine were even more attenuated in failing hearts, to a level 76-90% lower than those of nonfailing innervated hearts. In denervated, previously transplanted, nonfailing hearts, the contractile responses to the mixed agonists dopamine and dopexamine were 66-72% lower than those in the nonfailing innervated group, but the response to isoproterenol was not significantly different. The response to zinterol was not significantly different among the three groups. In subjects with severe heart failure, in vivo hemodynamic responses to dopexamine were compared with those of the direct-acting beta-agonist dobutamine. Responses to dopexamine and dobutamine were measured before and after prolonged continuous infusions of each drug. The response to dopexamine, but not to dobutamine, diminished over time. We conclude that a large component of the inotropic response to dopamine and dopexamine in human hearts is due to the ability of these agonists to promote the release of neuronal norepinephrine; when neuronal norepinephrine is depleted, indirect-acting agonists are less able to produce an inotropic response.

Vasoactive intestinal peptide receptor in failing human ventricular myocardium exhibits increased affinity and decreased density

We investigated vasoactive intestinal peptide (VIP)-receptor pharmacology in failing and nonfailing human ventricular myocardium by examining [125I]VIP binding in membrane fractions of left ventricle and inotropic effects of VIP in isolated right ventricular trabeculae mounted in tissue baths. [125I]VIP binding demonstrated upwardly concave, curvilinear Scatchard plots consistent with two classes of binding sites. Only the high-affinity (dissociation constant [Kd] 400-800 pM) site could be regulated by guanine nucleotides. Compared with nonfailing heart, membranes derived from failing heart exhibited a twofold reduction in the Kd of the high-affinity VIP binding site, whereas the receptor density (Bmax) was decreased by 62%. In concordance with this decreased receptor density and increased affinity, the maximal contractile response of right ventricular trabeculae from failing right ventricles was decreased by 61%, and the dose-response curve to VIP was left-shifted approximately threefold. We conclude that the VIP receptor in failing human ventricular myocardium exhibits novel regulatory behavior consisting of increased receptor affinity and decreased receptor density.

The beta-adrenergic receptor-adenylate cyclase complex as a target for therapeutic intervention in heart failure

In the human heart the beta-adrenergic pathways are the primary means of increasing cardiac performance in response to acute or chronic stress. Control of beta pathway function is achieved by changes in the receptors themselves, and to a lesser degree by adjustments in the inhibitory G protein (Gi). In heart failure myocardial beta-receptor function is substantially reduced, but the beta-receptor pathways are so powerful that they remain capable of supporting inotropic function. Certain therapeutic interventions that improve exercise performance in heart failure can partially restore beta-receptor pathway function to normal; these interventions include beta-blocker therapy and treatment with angiotensin converting enzyme inhibitors. Other types of therapy, such as chronic administration of beta-adrenergic agonists, may produce undesirable effects by increasing beta-receptor subsensitivity; however, the effects of beta-agonists on beta-receptor function are somewhat unpredictable and certain beta-agonists do not appear to produce much desensitization. Finally, the failing human heart is in effect partially denervated due to depletion of neuronal norepinephrine, and consequently in advanced heart failure beta-agonists that possess an indirect component of action will be less effective than exclusively direct-acting agents. These observations indicate that the baseline status and the intervention-associated behaviour of the human myocardial beta-adrenergic receptor systems need to be considered in developing therapeutic strategies in congestive heart failure.

Beta 1- and beta 2-adrenergic receptor-mediated adenylate cyclase stimulation in nonfailing and failing human ventricular myocardium

Prenalterol (beta 1-agonist), denopamine (beta 1-agonist), and zinterol (beta 2-agonist) were partial agonists of adenylate cyclase (AC) stimulation in human ventricular myocardium obtained from nonfailing chambers whose beta 1/beta 2 receptor subtype ratio was approximately 80/20. At a concentration less than its low affinity (beta 2) Kl, betaxolol, a highly selective beta 1-antagonist, inhibited isoproterenol (non-selective agonist), denopamine, and prenalterol stimulation of AC, indicating that isoproterenol, denopamine, and prenalterol are all capable of stimulating AC through beta 1-receptor activation. At a concentration less than its low affinity (beta 1) Kl, ICI 118,551, a highly selective beta 2-agonist, inhibited both isoproterenol and zinterol stimulation of AC, indicating that isoproterenol and zinterol stimulate AC through beta 2-receptors. Zinterol stimulation of AC was mediated entirely by beta 2-receptors, inasmuch as 10(-7) M betaxolol had no effect on the zinterol dose-response curve and ICI 118,551 produced a degree of blockade (KB = 5.2 +/- 1.6 X 10(-9) M), consistent with the beta 2-receptor Kl of the latter (2.0 +/- .4 X 10(-9) M, p, not significant). In nonfailing myocardium, analysis of beta 1 versus beta 2 stimulation by the nonselective agonist isoproterenol revealed that the numerically small (19% of the total) beta 2 fraction accounted for the majority of the total adenylate cyclase stimulation. In failing ventricular chambers with a beta 1/beta 2 receptor subtype ratio reduced from 82/19 (nonfailing) to 64/36 (p less than 0.001) and a beta 1-receptor density reduced by 61% (p less than 0.001), maximal denopamine stimulation was reduced by 49% (p less than 0.001). Moreover, in preparations from failing heart, the component of denopamine stimulation that was inhibited by 10(-7) M betaxolol (beta 1 component) was reduced by 77% (p less than 0.05). Finally, in preparations derived from failing ventricular myocardium, beta 2-receptor density was not significantly decreased, but zinterol stimulation of AC was reduced by 32% (p less than 0.05). We conclude that heart failure results in subsensitivity to both selective beta 1 and beta 2 stimulation of adenylate cyclase, with beta 1 subsensitivity due to selective beta 1 receptor down-regulation and beta 2 subsensitivity due to partial uncoupling of beta 2 receptors from subsequent events in the beta 2-adrenergic pathway.

Alpha-1 adrenergic receptors in the nonfailing and failing human heart

We examined alpha-1 adrenergic receptor density in ventricular myocardium from nonfailing and failing human hearts, utilizing the alpha-1 radioligand [125I]IBE2254. The alpha-1 receptor population comprised a relatively small portion of the total adrenergic receptors, 14.6 +/- 1.9%. However, in failing human ventricular myocardium the alpha-1 adrenergic receptor population constituted a much greater portion, 27.3 +/- 2.1% (P less than .01). The reason for the increased proportion of alpha-1 adrenergic receptors was not that the total concentration of alpha-1 receptors was increased, but instead was due to selective down-regulation of the beta-1 adrenergic receptor population. Beta-2 adrenergic receptors behaved similarly to alpha-1 adrenergic receptors in the failing human heart, and were increased in proportion and unchanged in total number. Additionally, the ability of alpha-1 stimulation to increase the incorporation of label from [3H]inositol into inositol phosphates was examined in tissue homogenates. Maximal doses of norepinephrine produced only marginal stimulation of phosphatidylinositol hydrolysis, in contrast to a more substantial response produced by muscarinic stimulation. We conclude that human ventricular myocardium contains alpha-1 adrenergic receptors that 1) are of relatively low density, 2) are unchanged in density by heart failure and 3) mediate relatively low-level stimulation of phosphatidylinositol hydrolysis.

Increase of the 40,000-mol wt pertussis toxin substrate (G protein) in the failing human heart

Human heart failure is associated with a diminished contractile response to beta-adrenergic agonists. We hypothesized that alterations in the activity of a guanine nucleotide-binding regulatory protein (G protein) might be partially responsible for this abnormality. We therefore measured the activity of G proteins in failing human myocardium utilizing bacterial toxin-catalyzed ADP ribosylation. The activity of a 40,000-mol wt pertussis toxin substrate (alpha G40) was increased by 36% in failing human hearts when compared with nonfailing controls. In contrast, there was no change in the level of the stimulatory regulatory subunit (Gs). The increased activity in alpha G40 was associated with a 30% decrease in basal as well as 5'-guanylyl imidodiphosphate-stimulated adenylate cyclase activity. These data suggest that increased alpha G40 activity is a new marker for failing myocardium and may account at least in part for the diminished responsiveness to beta 1-adrenergic agonists in the failing human heart.

Heterogeneous regulatory changes in cell surface membrane receptors coupled to a positive inotropic response in the failing human heart

The failing human ventricular myocardium undergoes heterogeneous changes at the receptor level that have some impact on the ability of the failing myocardium to respond to inotropic stimuli. In the failing human ventricular myocardium the beta 1-adrenergic receptor is profoundly down-regulated, the beta 2-adrenergic receptor is only slightly decreased, alpha 1-adrenergic receptors are unchanged and VIP receptors appear to be increased in density or affinity. These changes have implications for therapeutic strategies for heart failure and for the natural history and pathogenesis of heart muscle disease.

Treatment of central nervous system fungal infection with ketoconazole

Two patients with fungal infection of the central nervous system (coccidioidal meningitis and cerebral histoplasmomas) were treated with ketoconazole for 30 months. Both responded to dosages substantially less than those described previously for similar infections. Neither patient experienced any significant adverse effects from the prolonged therapy.