Clinical considerations of heritable factors in common heart failure

Contextualizing Genetics for Regional Heart Failure Care

Congestive heart failure (CHF) is a chronic and often devastating cardiovascular disorder with no cure. There has been much advancement in the last two decades that has seen improvements in morbidity and mortality. Clinicians have also noted variations in the responses to therapies. More detailed observations also point to clusters of diseases, phenotypic groupings, unusual severity and the rates at which CHF occurs. Medical genetics is playing an increasingly important role in answering some of these observations. This developing field in many respects provides more information than is currently clinically applicable. This includes making sense of the established single gene mutations or uncommon private mutations. In this thematic series which discusses the many factors that could be relevant for CHF care, once established treatments are available in the communities; this section addresses a contextual role for medical genetics.

Pharmacogenomics of heart failure: a systematic review

BACKGROUND

Heart failure (HF) and multiple HF-related phenotypes are heritable. Genes implicated in the HF pathophysiology would be expected to influence the response to treatment.

METHODS

We conducted a series of systematic literature searches on the pharmacogenetics of HF therapy to assess the current knowledge on this field.

RESULTS

Existing data related to HF pharmacogenomics are still limited. The ADRB1 gene is a likely candidate to predict response to β-blockers. Moreover, the cytochrome P450 2D6 coding gene (CYP2D6) clearly affects the pharmacokinetics of metoprolol, although the clinical impact of this association remains to be established.

CONCLUSION

Given the rising prevalence of HF and related costs, a more personalized use of HF drugs could have a remarkable benefit for patients, caregivers and healthcare systems.

Operationalizing Precision Cardiovascular Medicine: Three Innovations

For precision medicine to become a reality, we propose three changes. First, healthcare deliverables must be prioritized, enabling translation of knowledge to the clinic. Second, physicians and patients must be convinced to participate, requiring additional infrastructure in health systems. Third, discovery science must evolve to shift the preclinical landscape for innovation. We propose a change in the fundamental relationship between basic and clinical science: rather than two distinct entities between which concepts must be translated, we envision a natural hybrid of these approaches, wherein discovery science and clinical trials coincide in the same health systems and patient populations.

Impact of the β-1 adrenergic receptor polymorphism on tolerability and efficacy of bisoprolol therapy in Korean heart failure patients: association between β adrenergic receptor polymorphism and bisoprolol therapy in heart failure (ABBA) study

BACKGROUND/AIMS

We evaluated the association between coding region variants of adrenergic receptor genes and therapeutic effect in patients with congestive heart failure (CHF).

METHODS

One hundred patients with stable CHF (left ventricular ejection fraction [LVEF] < 45%) were enrolled. Enrolled patients started 1.25 mg bisoprolol treatment once daily, then up-titrated to the maximally tolerable dose, at which they were treated for 1 year.

RESULTS

Genotypic analysis was carried out, but the results were blinded to the investigators throughout the study period. At position 389 of the β-1 adrenergic receptor gene (ADRB1), the observed minor Gly allele frequency (Gly389Arg + Gly389Gly) was 0.21, and no deviation from Hardy-Weinberg equilibrium was observed in the genotypic distribution of Arg389Gly (p = 0.75). Heart rate was reduced from 80.8 ± 14.3 to 70.0 ± 15.0 beats per minute (p < 0.0001). There was no significant difference in final heart rate across genotypes. However, the Arg389Arg genotype group required significantly more bisoprolol compared to the Gly389X (Gly389Arg + Gly389Gly) group (5.26 ± 2.62 mg vs. 3.96 ± 2.05 mg, p = 0.022). There were no significant differences in LVEF changes or remodeling between two groups. Also, changes in exercise capacity and brain natriuretic peptide level were not significant. However, interestingly, there was a two-fold higher rate of readmission (21.2% vs. 10.0%, p = 0.162) and one CHF-related death in the Arg389Arg group.

CONCLUSIONS

The ADRB1 Gly389X genotype showed greater response to bisoprolol than the Arg389Arg genotype, suggesting the potential of individually tailoring β-blocker therapy according to genotype.

Genetics and heart failure: a concise guide for the clinician

The pathogenesis of heart failure involves a complex interaction between genetic and environmental factors. Genetic factors may influence the susceptibility to the underlying etiology of heart failure, the rapidity of disease progression, or the response to pharmacologic therapy. The genetic contribution to heart failure is relatively minor in most multifactorial cases, but more direct and profound in the case of familial dilated cardiomyopathy. Early studies of genetic risk for heart failure focused on polymorphisms in genes integral to the adrenergic and renin-angiotensin-aldosterone system. Some of these variants were found to increase the risk of developing heart failure, and others appeared to affect the therapeutic response to neurohormonal antagonists. Regardless, each variant individually confers a relatively modest increase in risk and likely requires complex interaction with other variants and the environment for heart failure to develop. Dilated cardiomyopathy frequently leads to heart failure, and a genetic etiology increasingly has been recognized in cases previously considered to be "idiopathic". Up to 50% of dilated cardiomyopathy cases without other cause likely are due to a heritable genetic mutation. Such mutations typically are found in genes encoding sarcomeric proteins and are inherited in an autosomal dominant fashion. In recent years, rapid advances in sequencing technology have improved our ability to diagnose familial dilated cardiomyopathy and those diagnostic tests are available widely. Optimal care for the expanding population of patients with heritable heart failure involves counselors and physicians with specialized training in genetics, but numerous online genetics resources are available to practicing clinicians.

Potential applications of pharmacogenomics to heart failure therapies

Pharmacogenomics explores one drug's varying effects on different patient genotypes. A better understanding of genomic variation's contribution to drug response can impact 4 arenas in heart failure (HF): (1) identification of patients most likely to receive benefit from therapy, (2) risk stratify patients for risk of adverse events, (3) optimize dosing of drugs, and (4) steer future clinical trial design and drug development. In this review, the authors explore the potential applications of pharmacogenomics in patients with HF in the context of these categories.

Transcriptomic biomarkers of cardiovascular disease

Transcriptomics is the study of how our genes are regulated and expressed in different biological settings. Technical advances now enable quantitative assessment of all expressed genes (ie, the entire "transcriptome") in a given tissue at a given time. These approaches provide a powerful tool for understanding complex biological systems and for developing novel biomarkers. This chapter will introduce basic concepts in transcriptomics and available technologies for developing transcriptomic biomarkers. We will then review current and emerging applications in cardiovascular medicine.