Calcium channel blockers in cardiac failure

The Protective Effect of Qishen Granule on Heart Failure after Myocardial Infarction through Regulation of Calcium Homeostasis

Qishen granule (QSG) is a frequently prescribed traditional Chinese medicine formula, which improves heart function in patients with heart failure (HF). However, the cardioprotective mechanisms of QSG have not been fully understood. The current study aimed to elucidate whether the effect of QSG is mediated by ameliorating cytoplasmic calcium (Ca²⁺) overload in cardiomyocytes. The HF rat model was induced by left anterior descending (LAD) artery ligation surgery. Rats were randomly divided into sham, model, QSG-low dosage (QSG-L) treatment, QSG-high dosage (QSG-H) treatment, and positive drug (diltiazem) treatment groups. 28 days after surgery, cardiac functions were assessed by echocardiography. Levels of norepinephrine (NE) and angiotensin II (AngII) in the plasma were evaluated. Expressions of critical proteins in the calcium signaling pathway, including cell membrane calcium channel CaV1.2, sarcoendoplasmic reticulum ATPase 2a (SERCA2a), calcium/calmodulin-dependent protein kinase type II (CaMKII), and protein phosphatase calcineurin (CaN), were measured by Western blotting (WB) and immunohistochemistry (IHC). Echocardiography showed that left ventricular ejection fraction (EF) and fractional shortening (FS) value significantly decreased in the model group compared to the sham group, and illustrating heart function was severely impaired. Furthermore, levels of NE and AngII in the plasma were dramatically increased. Expressions of CaV1.2, CaMKII, and CaN in the cardiomyocytes were upregulated, and expressions of SERCA2a were downregulated in the model group. After treatment with QSG, both EF and FS values were increased. QSG significantly reduced levels of NE and AngII in the plasma. In particular, QSG prevented cytoplasmic Ca²⁺ overload by downregulating expression of CaV1.2 and upregulating expression of SERCA2a. Meanwhile, expressions of CaMKII and CaN were inhibited by QSG treatment. In conclusion, QSG could effectively promote heart function in HF rats by restoring cardiac Ca²⁺ homeostasis. These findings revealed novel therapeutic mechanisms of QSG and provided potential targets in the treatment of HF.

Clinically important drug interactions potentially involving mechanism-based inhibition of cytochrome P450 3A4 and the role of therapeutic drug monitoring

Cytochrome P450 (CYP) 3A4 is the most abundant enzyme of CYPs in the liver and gut that metabolizes approximately 50% currently available drugs. A number of important drugs have been identified as substrates, inducers, and/or inhibitors of CYP3A4. The substrates of CYP3A4 considerably overlap with those of P-glycoprotein. Both CYP3A4 and P-glycoprotein are subject to inhibition and induction by a number of factors. Mechanism-based inhibition of CYP3A4 is characterized by NADPH-, time-, and concentration-dependent enzyme inactivation occurring when some xenobiotics or drugs are converted by CYPs to reactive metabolites. Such an inhibition of CYP3A4 is caused by chemical modification of the heme, the protein, or both as a result of covalent binding of modified heme to the protein. To date, the identified clinically important mechanism-based CYP3A4 inhibitors mainly include macrolide antibiotics (eg, clarithromycin and erythromycin), anti-HIV agents (eg, ritonavir and delavirdine), antidepressants (eg, fluoxetine and fluvoxamine), calcium channel blockers (eg, verapamil and diltiazem), steroids and their modulators (eg, gestodene and mifepristone), and several herbal and dietary components. The inactivation of CYP3A4 by drugs often causes unfavorable and long-lasting drug-drug interactions and probably fatal toxicity, depending on many factors associated with the enzyme, drugs, and the patients. Clinicians are encouraged to have a sound knowledge of drug-induced, mechanism-based CYP3A4 inhibition; take proper cautions, and perform close monitoring for possible drug interactions when using drugs that are mechanism-based CYP3A4 inhibitors. To minimize drug-drug interactions involving mechanism-based CYP3A4 inhibition, it is necessary to choose safe drug combination regimens, adjust drug dosages appropriately, and conduct therapeutic drug monitoring for drugs with narrow therapeutic indices.

Defining the role of calcium channel antagonists in heart failure due to systolic dysfunction

Calcium channel antagonists (CCAs) may either be divided into the dihydropyridines (e.g. amlodipine, felodipine, isradipine, lacidipine, nilvadipine, nifedipine, nicardipine etc.), the phenylalkylamines (e.g. verapamil) and the benzothiazepines (e.g. diltiazem) according to their chemical structure, or into first generation agents (nifedipine, verapamil and diltiazem) and second generation agents (subsequently developed dihydropyridine-derivatives). Second generation CCAs are characterized by greater selectivity for calcium channels in vascular smooth muscle cells than the myocardium, a longer duration of action and a small trough-to-peak variation in plasma concentrations. Heart failure is characterized by decreased cardiac output resulting in inadequate oxygen delivery to peripheral tissues. Although the accompanying neurohormonal activation, leading to vasoconstriction and increased blood pressure, is initially beneficial in increasing tissue perfusion, prolonged activation is detrimental because it increases afterload and further reduces cardiac output. At the level of the myocyte, heart failure is associated with increased intracellular calcium levels which are thought to impair diastolic function. These changes indicate that the CCAs would be beneficial in patients with heart failure. There has been a strong interest and increasing experience in the use of CCAs in patients with heart failure. Despite potential beneficial effects in initial small trials, findings from larger trials suggest that CCA may have detrimental effects upon survival and cardiovascular events. However, this may not necessarily be a 'class b' effect of the CCAs as there is considerable heterogeneity in the chemical structure of individual agents. Clinical experience with different CCAs in patients with heart failure includes trials that evaluated their effects on hemodynamic parameters, exercise tolerance and on symptomatology. However, the most relevant results are those from randomized clinical trials that assessed mortality as the primary endpoint. First generation CCAs have direct negative inotropic effects and even sustained release formulations have not proved any beneficial effect upon survival. With second generation CCAs, some benefit on hemodynamic parameters has been observed but none on survival, alone or in combination with ACE inhibitors. It is noteworthy that although amlodipine had a neutral effect on morbidity and mortality in large, randomized, placebo-controlled trials in patients with heart failure, the drug was well tolerated. There is no specific indication for CCAs (first or second generation) in patients with systolic heart failure, alone or in combination with ACE inhibitors, but amlodipine may be a considered in the management of hypertension or coronary artery disease in patients with heart failure.

Heart Failure in Older Adults: Providing Nursing Care to Improve Outcomes

Heart failure continues to be a challenge for older patients and their health care providers. This article is based on work by advanced practice nurses in a nursing study funded by the National Institute of Nursing Research of the National Institute of Health. Mary Naylor, RN, PhD at the University of Pennsylvania School of Nursing through grant #1RO1-NR04315 is using a transitional care model to provide advance practice nurse intervention for older adults with heart failure in a randomized controlled trial. Effects of the intervention being addressed include quality of life, functional status, rehospitalizations, and costs of care. Working with the patient in the acute hospital setting and following patients to the home care setting for 3 months, the advance practice nurse develops a visit pattern and intervention plan individual to the patient's needs. Key to a successful intervention plan is the right treatment for systolic versus diastolic failure. Although the patient's symptoms and some physical findings may be similar, the drugs used to treat systolic versus diastolic heart failure are different. Thus the nursing interventions to promote symptom management and avoid rehospitalizations have a different approach. In this article, care of elderly individuals with systolic versus diastolic heart failure is compared and contrasted using physical examination and diagnostic techniques, medication management, and nursing intervention. Case studies of a typical patient with systolic and diastolic heart failure will be used to illustrate the differences in approach to this common group of patients with complex needs.

Effects of first and second generation calcium channel blockers on diastolic function of the failing hamster heart: relationship with coronary flow changes

Calcium channel blockers (CCBs) have variable efficacy in the treatment of heart failure. We hypothesized that modulation of left ventricular diastolic pressure (LVDP) may play a role in the variable efficacy of CCBs in this condition. Isolated perfused hearts from 200- to 250-day-old UM-X7.1 cardiomyopathic hamsters (failing hearts) and age-matched Syrian hamsters (normal hearts) were studied. After recording of heart rate, coronary flow (CF), LVDP and left ventricular systolic pressure (LVSP), hearts were exposed either to verapamil or diltiazem (1 nM-10 microM), mibefradil (1 nM-1 microM) or clentiazem (1 nM-10 microM). Mechanical increase in CF (+2 to +10 ml/min) was carried out using a roller pump. Mechanically-augmented flow led to an increase in coronary perfusion pressure (+40 to +90 mm Hg), LVSP (+5 to +40 mm Hg) and LVDP (+5 to +25 mm Hg). CCBs-induced increment of coronary flow led to a difference in their cardiac response. In normal hearts, the negative inotropic response was more important with diltiazem and verapamil. Failing hearts did not demonstrate increased inotropic sensitivity to first-generation CCBs. On the contrary, at clinically relevant concentrations, verapamil resulted in the most pronounced impairment of LVDP followed by diltiazem while mibefradil and clentiazem, at clinically relevant concentrations, preserved LVDP. Such findings provide an additional explanation for the variable efficacy of CCBs in heart failure.

Differential gene expression technologies for identifying surrogate markers of drug efficacy and toxicity

Advances in the rapidly evolving discipline of pharmacogenomics have forced the biotechnology and pharmaceutical industries to integrate differential gene expression profiling into their drug discovery and development strategies. Here we highlight the use of differential gene expression technologies for the elucidation of both drug efficacy and toxicity as well as novel candidate genes for pharmacogenetic analyses to assess individual variability to drug response. This will include an overview of the different technologies created to facilitate pharmacogenomic analyses and to highlight advantages and disadvantages of these emerging methodologies. Two high-throughput differential gene expression technologies, microarrays and GeneCalling((R)), will be presented in detail.

Idiopathic Cardiomyopathy

Idiopathic cardiomyopathy is a very common cause of heart failure today. It is a diagnosis of exclusion, and careful attention should be paid to the patient history to exclude all other causes. ACE inhibitors have become the first line therapy for all classes of left ventricular dysfunction. Doses of all therapeutic drugs for CHF should be up-titrated to maximum targeted dosages. New agents are being developed that offer increasing hope for therapies that will alter the natural history of heart failure.

N-Type calcium channels control sympathetic neurotransmission in human heart atrium

BACKGROUND

Because knowledge about the type of calcium channels involved in action potential-induced norepinephrine release from the human peripheral sympathetic nervous system is sparse, we investigated which types of calcium channels are functionally important in the sympathetic nerves of human cardiac tissue.

METHODS AND RESULTS

In superfused segments of human right atrial appendages, the type of calcium channels that control [(3)H]norepinephrine release evoked by transmural electrical stimulation was determined. [(3)H]norepinephrine release was almost abolished by 0.2 micromol/L omega-conotoxin GVIA (a selective blocker of N-type channels) but was not modified by 0.1 micromol/L omega-agatoxin IVA (a selective blocker of P- and Q-type channels). Mibefradil (a T-type and N-type calcium channel blocker) at concentrations of 0.3 to 3 micromol/L reduced the evoked tritium overflow in a frequency- and calcium-dependent manner, whereas 0.1 to 10 micromol/L amlodipine, diltiazem, and verapamil (selective blockers of L-type channels) were ineffective.

CONCLUSIONS

Norepinephrine release from cardiac sympathetic nerves is triggered by Ca(2+) influx via N-type but not L- and P/Q-type calcium channels. The inhibitory effect of mibefradil on norepinephrine release at clinically relevant concentrations is probably due to its blocking action on N-type Ca(2+) channels. This property of mibefradil is unique among the calcium channel blockers that have been or still are therapeutically applied and may considerably contribute to its slight negative chronotropic effect in vivo.

Recalcitrant oral ulcers caused by calcium channel blockers: diagnosis and treatment considerations

BACKGROUND

Oral ulcers often pose a dilemma in diagnosis and treatment. Patients seen routinely in dental practices are frequently receiving multiple medications. The authors discuss the pathogenesis, clinical appearance and treatment of drug-induced oral ulcers.

CASE DESCRIPTIONS

Two patients with recalcitrant painful oral ulcers caused by calcium channel blockers are described. These ulcers failed to heal despite repeated interventions, including surgery, laser ablation, and topical and systemic steroid therapy. Results of the histopathologic examinations were nonspecific. The patients were in a great deal of pain because of the initial failure to recognize the cause of these ulcers.

CLINICAL IMPLICATIONS

A careful medical history, including a detailed list of medications received, is critical in identifying drug-induced oral ulcerations, especially when the ulcer is resistant to treatment and of indeterminate cause. To date, calcium channel blockers have not been reported to cause oral ulcerations.