Effect of alpha1-adrenoceptor blockade on coronary vasodilator reserve in cardiac syndrome X

Pharmacotherapy in patients with vasomotor disorders

Background

Anginal symptoms in patients with non-obstructive coronary artery disease are frequently related to vasomotor disorders of the coronary circulation. Although frequently overlooked, a distinct diagnosis of different vasomotor disorders can be made by intracoronary function testing. Early detection and treatment seems beneficial, but little evidence is available for the medical treatment of these disorders. Nevertheless, there are several pharmacotherapeutic options available to treat these patients and improve quality of life.

Methods & findings

We performed an extensive yet non-systematic literature search to explore available pharmacotherapeutic strategies for addressing vasomotor disorders in individuals experiencing angina and non-obstructive coronary artery disease. This article presents a comprehensive overview of therapeutic possibilities for patients exhibiting abnormal vasoconstriction (such as spasm) and abnormal vasodilation (like coronary microvascular dysfunction).

Conclusion

Treatment of vasomotor disorders can be very challenging, but a general treatment algorithm based on the existing evidence and the best available current practice is feasible.

Vasomotor Dysfunction in Patients with Ischemia and Non-Obstructive Coronary Artery Disease: Current Diagnostic and Therapeutic Strategies

Many patients who present with symptoms or objective evidence of ischemia have no or non-physiologically-significant disease on invasive coronary angiography. The diagnosis of ischemic heart disease is thus often dismissed, and patients receive false reassurance or other diagnoses are pursued. We now know that a significant proportion of these patients have coronary microvascular dysfunction and/or vasospastic disease as the underlying pathophysiology of their clinical presentation. Making the correct diagnosis of such abnormalities is important not only because they impact the quality of life, with recurring symptoms and unnecessary repeated testing, but also because they increase the risk for adverse cardiovascular events. The mainstay of diagnosis remains an invasive comprehensive physiologic assessment, which further allows stratifying these patients into appropriate “endotypes”. It has been shown that tailoring treatment to the patient’s assigned endotype improves symptoms and quality of life. In addition to the conventional drugs used in chronic stable angina, multiple newer agents are being investigated. Moreover, innovative non-pharmacologic and interventional therapies are emerging to provide a bail-out in refractory cases. Many of these novel therapies fail to show consistent benefits, but others show quite promising results.

Management of ischaemia with non-obstructive coronary arteries (INOCA)

Up to half of patients undergoing elective coronary angiography for the investigation of chest pain do not present with evidence of obstructive coronary artery disease. These patients are often discharged with a diagnosis of non-cardiac chest pain, yet many could have an ischaemic basis for their symptoms. This type of ischaemic chest pain in the absence of obstructive coronary artery disease is referred to as INOCA (ischaemia with non-obstructive coronary arteries). This comprehensive review of INOCA management looks at why these patients require treatment, who requires treatment based on diagnostic evaluation, what clinical treatment targets should be considered, how to treat patients using a personalised medicine approach, when to initiate treatment, and where future research is progressing.

Treatment strategies in coronary microvascular dysfunction: A systematic review of interventional studies

CMD has been associated with a wide spectrum of diseases and conditions, and it has proven to be a strong prognostic marker of morbidity and mortality. Despite increased attention, guideline-based treatment recommendations are lacking. We performed a systematic review of pharmacological and nonpharmacological interventions to improve coronary perfusion, assessed by IC Doppler, TTDE, PET, CMRI, transthoracic contrast perfusion echocardiography, and dilution techniques. No restrictions were made regarding the study design (randomized, placebo-controlled/randomized with active comparators/nonrandomized with or without a control group), the cardiac condition studied, or the coronary microvascular function at baseline. An electronic database search yielded 4485 records of which 80 studies met our inclusion criteria. Included studies were sorted according to intervention and study design. Studies were small and heterogeneous in methodology, and only few were placebo-controlled. Although some treatments looked promising, we found that no specific treatment was sufficiently well documented to be recommended in any patient groups. There is a need for larger well-designed clinical trials, and we suggest that future studies stratify study populations according to pathogenic mechanisms, thereby investigating whether an individualized treatment approach would be more successful.

Coronary Slow-Flow Phenomenon as an Underrecognized and Treatable Source of Chest Pain: Case Series and Literature Review

Background. Coronary slow-flow phenomenon (CSFP) is characterized by delayed distal vessel opacification of contrast, in the absence of significant epicardial coronary stenosis. CSFP has been reported as a cause of chest pain and abnormal noninvasive ischemic tests and is often underrecognized. Material and Methods. Charts and angiographic records from our institution were reviewed to identify 15 consecutive patients who were diagnosed with CSFP from January 2016 to January 2017. Results. Of the 15 patients (4 females and 11 males) studied, the mean age was 59.1 years (range = 45-86 years); all had left ventricular ejection fraction >45% and without significant valvular stenosis/regurgitation. The indication for coronary angiography for all 15 patients was chest pain with abnormal noninvasive tests. Of the 11 patients who underwent previous coronary angiograms, all revealed prior evidence of CSFP. None of these patients were on calcium channel blockers (CCBs) or long-acting nitroglycerin agents before angiography. Intracoronary CCBs were effectively utilized to alleviate the angiographic finding (improvement in Thrombolysis in Myocardial Infarction frame count) in all 15 patients. Oral CCBs were started with subsequent improvement in all 15 patients (mean follow-up time = 13.6 months). Conclusion. Coronary slow-flow should be a diagnostic consideration in patients presenting with chest pain and abnormal noninvasive ischemic testing with nonobstructive epicardial vessels. CSFP remains underrecognized, and the specific standard of care for treatment has not been established. In each of the 15 cases, intracoronary nifedipine resolved the angiographic manifestation of coronary slow-flow. Furthermore, in follow-up, all patients improved symptomatically from their chest pain after oral CCBs were initiated.

Coronary microvascular dysfunction, microvascular angina, and treatment strategies

Angina without coronary artery disease (CAD) has substantial morbidity and is present in 10% to 30% of patients undergoing angiography. Coronary microvascular dysfunction (CMD) is present in 50% to 65% of these patients. The optimal treatment of this cohort is undefined. We performed a systematic review to evaluate treatment strategies for objectively-defined CMD in the absence of CAD. We included studies assessing therapy in human subjects with angina and coronary flow reserve or myocardial perfusion reserve <2.5 by positron emission tomography, cardiac magnetic resonance imaging, dilution methods, or intracoronary Doppler in the absence of coronary artery stenosis ≥50% or structural heart disease. Only 8 papers met the strict inclusion criteria. The papers were heterogeneous, using different treatments, endpoints, and definitions of CMD. The small sample sizes severely limit the power of these studies, with an average of 11 patients per analysis. Studies evaluating sildenafil, quinapril, estrogen, and transcutaneous electrical nerve stimulation application demonstrated benefits in their respective endpoints. No benefit was found with L-arginine, doxazosin, pravastatin, and diltiazem. Our systematic review highlights that there is little data to support therapies for CMD. We assess the data meeting rigorous inclusion criteria and review the related but excluded published data. We additionally describe the next steps needed to address this research gap, including a standardized definition of CMD, routine assessment of CMD in studies of chest pain without obstructive CAD, and specific therapy assessment in the population with confirmed CMD.

Etiopathogenesis of microvascular angina: caveats in our knowledge

Nearly 50% of subjects of coronary artery disease suffer from coronary microvascular dysfunction. Various etiopathogenetic factors have been proposed by different workers but no hypothesis can explain the genesis of microvascular angina in all patients. We have made an attempt to review the literature to find caveats in our knowledge so that future studies can be better designed.

Management of microvascular angina pectoris

Microvascular angina (MVA) is defined as angina pectoris caused by abnormalities of small coronary arteries. In its most typical presentation, MVA is characterized by angina attacks mainly caused by effort, evidence of myocardial ischemia on non-invasive stress tests, but normal coronary arteries at angiography. Patients with stable MVA have excellent long-term prognoses, but often present with persistent and/or worsening of angina symptoms. Treatment of MVA is initially based on standard anti-ischemic drugs (beta-blockers, calcium antagonists, and nitrates), but control of symptoms is often insufficient. In these cases, several additional drugs, with different potential anti-ischemic effects, have been proposed, including ranolazine, ivabradine, angiotensin-converting enzyme (ACE) inhibitors, xanthine derivatives, nicorandil, statins, alpha-blockers and, in perimenopausal women, estrogens. In patients with 'refractory MVA', some further alternative therapies (e.g., spinal cord stimulation, pain-inhibiting substances such as imipramine, rehabilitation programs) have shown favorable results.

Cardiac syndrome X. Diagnosis, pathogenesis and management

Patients with cardiac syndrome X (typical chest pain and normal coronary arteriograms) represent a heterogeneous syndrome, which encompasses different pathogenic mechanisms. Although symptoms in most patients with cardiac syndrome X are non-cardiac, a sizable proportion of them have angina pectoris due to transient myocardial ischemia. Thus radionuclide myocardial perfusion defects, coronary sinus oxygen saturation abnormalities and pH changes, myocardial lactate production and stress-induced alterations of cardiac high energy phosphate suggest an ischemic origin of symptoms in at least a proportion of patients with cardiac syndrome X. Microvascular abnormalities, caused by endothelial dysfunction, appear to be responsible for myocardial ischemia in patients with cardiac syndrome X. Endothelial dysfunction is likely to be multifactorial in these patients and it is conceivable that risk factors such as hypertension, hypercholesterolemia, diabetes mellitus and smoking can contribute to its development. Most patients with cardiac syndrome X are postmenopausal women and estrogen deficiency has been therefore proposed as a pathogenic factor in female patients. Additional factors such as abnormal pain perception may contribute to the pathogenesis of chest pain in patients with angina pectoris and normal coronary angiograms. Although prognosis is good regarding survival, patients with cardiac syndrome X have an impaired quality of life. Management of this syndrome represents a major challenge to the treating physician. Understanding the mechanism underlying the condition is of vital importance for patient management. Thus diagnostic tests should aim at identifying the cause of the symptoms in the individual patient, i.e. myocardial ischemia, increased pain perception, abnormalities of adrenergic tone, non-cardiac mechanisms, etc. Moreover, it is important to bear in mind that treatment of cardiac syndrome X should be mainly directed towards improving quality of life, as prognosis is usually good in these patients. Conventional antianginal agents such nitrates, calcium channel antagonists, beta-adrenoceptor antagonists and nicorandil are effective particularly in patients in whom chest pain and ECG changes are clearly suggestive of myocardial ischemia and in those with objective documentation of ischemia. Angiotensin-converting enzyme inhibitors have been shown to be useful in syndrome X patients with increased adrenergic tone, borderline systemic hypertension, and those with documented endothelial dysfunction. Analgesic interventions of different sorts have been proposed based on the hypothesis that somatic and visceral perception of pain is altered in cardiac syndrome X patients. Pharmacological agents such as imipramine and aminophylline, and neural electrical stimulation techniques have been assessed in recent years with encouraging results. Psychological treatment, particularly cognitive therapy, appears to be useful in defined patient subsets. Relaxation techniques such as transcendental meditation have been successfully used in small studies and shown to improve not only chest pain but also exercise-induced ST segment changes. Reports indicate that these techniques improve quality of life.

Doxazosin and congestive heart failure

Doxazosin remains a commonly used antihypertensive medication, although its use has been tainted by recent findings from the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). ALLHAT was a large, simple trial, designed in a fashion to closely mimic clinical practice as it occurs in high-risk hypertensive patients aged 55 years or older. Its goals were to determine whether the incidence of the primary outcome--a composite of fatal coronary heart disease and nonfatal myocardial infarction--differed between treatment with a diuretic (chlorthalidone) (12.5-25.0 mg/day) and treatment with each of three other types of antihypertensive drugs-a calcium-channel blocker (amlodipine), an angiotensin-converting enzyme inhibitor (lisinopril), and a peripheral alpha-adrenergic blocker (doxazosin) (2-8 mg/day). Doxazosin was recently withdrawn from this trial after an interim analysis showed the secondary end point of combined cardiovascular disease to be 25% greater in patients on doxazosin than in those assigned to treatment with chlorthalidone. This finding was largely driven by congestive heart failure. The practicing clinician should not abandon doxazosin completely because of the ALLHAT findings, although these findings are indisputably important. These results represent an interim analysis and their application to clinical practice needs to occur carefully. A valued member of our therapeutic armamentarium need not be laid entirely to rest; rather, doxazosin should now be viewed as a secondary or tertiary antihypertensive therapy pending a more complete review of the ALLHAT data.

Premature termination of clinical trials--lessons learned

Controlled clinical trials in cardiovascular disease are the cornerstone for therapeutic advances in this field of medicine. Since the introduction of the concept of controlled clinical trials there has been substantial progress in the design, conduct, and analysis of such studies. A growing awareness of ethical issues emerging from such trials has heightened public awareness, increased investigator scrutiny, and reinforced the need for interim data analysis. A benefit of such interim analyses is that either an entire clinical trial or a specific treatment limb can be stopped if the observed findings argue for premature termination. For example, highly positive findings, as were noted in the HOPE Study (Heart Outcomes Prevention Evaluation), led to its being stopped after 4.5 years of treatment, which was 1 year early. Alternatively, the doxazosin treatment limb of the ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) and the amlodipine treatment limb of AASK (African American Study of Kidney Disease and Hypertension) were stopped early because of negative findings with each respectively. Finally, economic considerations can enter into the decision to close a study early as was the case in the CONVINCE (Controlled Onset Verapamil Investigation of Cardiovascular End Points) trial. Most such decisions rely heavily on information obtained from independent data and safety monitoring boards. Such boards ensure patient safety by providing an unbiased ongoing review of data, which would otherwise be unavailable until a study's completion. Early termination of a clinical trial can have important clinical implications and, in particular, can redirect patterns of clinical practice.

Pharmacotherapy in congestive heart failure. Prematurely terminated clinical trials and their application to cardiovascular medicine

Controlled clinical trials in cardiovascular disease remain the cornerstone of field-specific therapeutic advances. Since the introduction of the concept of controlled clinical trials, there has been considerable fine-tuning of the design, conduct, and analysis of such studies. A growing awareness of ethical issues emerging from such trials has led to increased public and investigator scrutiny and the routine requirement for both interim data analysis and full conflict-of-interest disclosure. A benefit of such interim analyses is that either an entire clinical trial or a specific treatment limb can be stopped if the observed findings warrant early termination. For example, highly positive findings, as were noted in the HOPE Study (Heart Outcomes Prevention Evaluation), led to its closure after 4.5 years of treatment, which was 1 year earlier than anticipated. Also, the doxazosin treatment limb of ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) and the amlodipine treatment limb of AASK (African American Study of Kidney Disease and Hypertension) were stopped early, because of negative findings in one of their treatment limbs. Finally, economic considerations can enter into the decision to close a study early, as was the case in the CONVINCE (Controlled-Onset Verapamil Investigation of Cardiovascular Endpoints) trial. Most such decisions rely heavily on information obtained from independent data and safety monitoring boards. Such boards ensure patient safety by providing an unbiased, ongoing review of data, which would otherwise be unavailable until a study's completion. Early termination of a clinical trial can have important clinical and economic implications and, in particular, can substantially redirect the pattern of clinical practice. (c)2001 CHF, Inc.

Lessons learned from prematurely terminated clinical trials

Controlled clinical trials in cardiovascular disease are the cornerstone for therapeutic advances in this field of medicine. Since the introduction of the concept of controlled clinical trials, there has been substantial progress in the design, conduct, and analysis of such studies. A growing awareness of ethical issues emerging from such trials has led to increased public and investigator scrutiny, and the routine requirement for interim data analysis. A benefit of such interim analysis is that either an entire clinical trial or a specific treatment limb can be stopped if the observed findings warrant premature termination. For example, highly positive findings, as were noted in the Heart Outcomes Prevention Evaluation (HOPE) study, led to its closure about 1 year early after 4.5 years of treatment. Alternatively, the doxazosin treatment limb of the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) and the amlodipine treatment limb of the African-American Study of Kidney Disease and Hypertension (AASK) were stopped early because of negative findings. Finally, economic considerations can enter into the decision to close a study early as was the case in the Controlled ONset Verapamil INvestigation of Cardiovascular Endpoints (CONVINCE) trial. Most such decisions rely heavily on information obtained from independent data and safety monitoring boards. Such boards ensure patient safety by providing an unbiased ongoing review of data, which would otherwise be unavailable until a study's completion. Early termination of a clinical trial can have important clinical implications and, in particular, can redirect patterns of clinical practice.

alpha-adrenergic coronary vasoconstriction and myocardial ischemia in humans

The use of quantitative coronary angiography, combined with Doppler and PET, has recently been directed at the study of alpha-adrenergic coronary vasomotion in humans. Confirming prior animal experiments, there is no evidence of alpha-adrenergic coronary constrictor tone at rest. Again confirming prior experiments, responses to alpha-adrenoceptor activation are augmented in the presence of coronary endothelial dysfunction and atherosclerosis, involving both alpha(1)- and alpha(2)-adrenoceptors in epicardial conduit arteries and microvessels. Such augmented alpha-adrenergic coronary constriction is observed during exercise and coronary interventions, and it is powerful enough to induce myocardial ischemia and limit myocardial function. Recent studies indicate a genetic determination of alpha(2)-adrenergic coronary constriction.