Fractional Flow Reserve and Instantaneous Wave-Free Ratio as Predictors of the Placebo-Controlled Response to Percutaneous Coronary Intervention in Stable Single-Vessel Coronary Artery Disease

The State of Percutaneous Intervention in Stable Coronary Artery Disease

PURPOSE OF REVIEW

This review examines trials of percutaneous coronary intervention (PCI) compared with optimal medical therapy (OMT) in order to inform clinical decision-making regarding the role of PCI in stable ischemic heart disease (SIHD).

RECENT FINDINGS

Several large, randomized, controlled trials published in recent years suggest that OMT should be the initial treatment strategy for symptomatic SIHD, but there is a role for PCI in patients who continue to be symptomatic despite OMT. Additionally, using fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) techniques may help to identify physiologically significant lesions and may be useful in maximizing the benefit from PCI in SIHD. Recent trials demonstrate PCI for the treatment of symptomatic SIHD does not reduce mortality compared with OMT but effectively relieves anginal symptoms. However, OMT continues to be the first-line therapy for SIHD but is significantly underutilized.

iFR uncovers profound but mostly reversible ischemia in CTOs and helps to optimize PCI results

OBJECTIVES

The study aimed to demonstrate through instant wave-free ratio (iFR) measurements that myocardium distal to a chronic total occlusion (CTO) is ischemic, that ischemia is reversible by PCI, and that iFR assessment after PCI can be used to optimize PCI results.

BACKGROUND

The greatest benefit of revascularization is found in patients with low fractional flow reserve. In patients with CTOs, iFR measurement may be more appropriate to evaluate ischemia as it does not require maximal microvascular vasodilation, which may be hampered by microvascular dysfunction.

METHODS

The iFR was measured in 81 CTO patients, both pre- and post-PCI in 63 patients, and only post-PCI in the following 18 patients. A pressure wire pullback was performed post-PCI if iFR ≤0.89.

RESULTS

The first 63 patients all had significant ischemia distal to the CTO with a median iFR of 0.33 [0.22; 0.44], improving significantly post-PCI to a median iFR of 0.93 [0.89;0.96] (p < .001). In the complete cohort, the median iFR post-PCI was 0.93 [0.86;0.96] but still ≤0.89 in 23 patients (30%). 12 of these patients had further PCI optimization because of a residual focal pressure gradient on pullback, after which only two had a final iFR ≤0.89.

CONCLUSIONS

In CTO patients with an indication for PCI, iFR consistently demonstrated profound myocardial ischemia. Successful PCI immediately relieved ischemia in 70% of patients. In the remaining 30% of cases, a manual iFR pullback proved helpful in guiding further optimization of the PCI result.

The argument of the ORBITA study: angioplasty is useless

The goal of treatment in stable coronary artery disease is to improve prognosis and quality of life of the patients. International Guidelines support revascularization procedures for symptomatic patients unresponsive to optimal medical treatment. Previous studies demonstrated, in fact, the therapeutic efficacy of coronary angioplasty in reducing angina and improving the functional capacity of these patients. The ORBITA study, recently published, challenged these assertions by demonstrating the lack of benefit of angioplasty over placebo in terms of effort tolerance in a population of patients with single-vessel coronary artery disease. What lesson could we learn from the ORBITA study?

Health-Status Outcomes with Invasive or Conservative Care in Coronary Disease

BACKGROUND

In the ISCHEMIA trial, an invasive strategy with angiographic assessment and revascularization did not reduce clinical events among patients with stable ischemic heart disease and moderate or severe ischemia. A secondary objective of the trial was to assess angina-related health status among these patients.

METHODS

We assessed angina-related symptoms, function, and quality of life with the Seattle Angina Questionnaire (SAQ) at randomization, at months 1.5, 3, and 6, and every 6 months thereafter in participants who had been randomly assigned to an invasive treatment strategy (2295 participants) or a conservative strategy (2322). Mixed-effects cumulative probability models within a Bayesian framework were used to estimate differences between the treatment groups. The primary outcome of this health-status analysis was the SAQ summary score (scores range from 0 to 100, with higher scores indicating better health status). All analyses were performed in the overall population and according to baseline angina frequency.

RESULTS

At baseline, 35% of patients reported having no angina in the previous month. SAQ summary scores increased in both treatment groups, with increases at 3, 12, and 36 months that were 4.1 points (95% credible interval, 3.2 to 5.0), 4.2 points (95% credible interval, 3.3 to 5.1), and 2.9 points (95% credible interval, 2.2 to 3.7) higher with the invasive strategy than with the conservative strategy. Differences were larger among participants who had more frequent angina at baseline (8.5 vs. 0.1 points at 3 months and 5.3 vs. 1.2 points at 36 months among participants with daily or weekly angina as compared with no angina).

CONCLUSIONS

In the overall trial population with moderate or severe ischemia, which included 35% of participants without angina at baseline, patients randomly assigned to the invasive strategy had greater improvement in angina-related health status than those assigned to the conservative strategy. The modest mean differences favoring the invasive strategy in the overall group reflected minimal differences among asymptomatic patients and larger differences among patients who had had angina at baseline. (Funded by the National Heart, Lung, and Blood Institute and others; ISCHEMIA ClinicalTrials.gov number, NCT01471522.).

Evaluation of Myocardial Ischemia with iFR (Instantaneous Wave-Free Ratio in the Catheterization Laboratory: A Pilot Study

BACKGROUND

The Instantaneous Wave-Free Ratio (iFR) is an invasive functional evaluation method that does not require vasoactive drugs to induce maximum hyperemia.

OBJECTIVE

To evaluate the contribution of the iFR to the therapeutic decision-making of coronary lesions in the absence of non-invasive diagnostic methods for ischemia, or in case of discordance between these methods and coronary angiography.

METHOD

We studied patients older than 18 years, of both sexes, consecutively referred for percutaneous treatment between May 2014 and March 2018. Coronary stenotic lesions were classified by visual estimation of the stenosis diameter into moderate (41-70% stenosis) or severe (71%-90%). An iFR ≤ 0.89 was considered positive for ischemia. Logistic regression was performed using the elastic net, with placement of stents as outcome variable, and age, sex, arterial hypertension, diabetes, dyslipidemia, smoking, family history, obesity and acute myocardial infarction (AMI) as independent variables. Classification trees, ROC curves, and Box Plot graphs were constructed using the R software. A p-value < 0.05 was considered statistically significant.

RESULTS

Fifty-two patients with 96 stenotic lesions (56 moderate, 40 severe) were evaluated. The iFR cut-off point of 0.87 showed a sensitivity of 0.57 and 1-specificity of 0.88, demonstrating high accuracy in reclassifying the lesions. Diabetes mellitus, dyslipidemia, and presence of moderate lesions with an iFR < 0.87 were predictors of stent implantation. Stents were used in 32% of lesions in patients with stable coronary artery disease and AMI with or without ST elevation (non-culprit lesions).

CONCLUSION

The iFR has an additional value to the therapeutic decision making in moderate and severe coronary stenotic lesions, by contributing to the reclassification of lesions and decreasing the need for stenting.

Association of Improvement in Fractional Flow Reserve With Outcomes, Including Symptomatic Relief, After Percutaneous Coronary Intervention

Importance

Whether the improvement in myocardial perfusion provided by percutaneous coronary intervention (PCI) is associated with symptomatic relief or improved outcomes has not been well investigated.

Objective

To investigate the prognostic value of the improvement in fractional flow reserve (FFR) after PCI (ΔFFR) on patients' symptoms and 2-year outcomes.

Design, Setting, and Participants

This study is a post hoc analysis of data from patients undergoing FFR-guided PCI in the randomized clinical trials Fractional Flow Reserve vs Angiography for Multivessel Evaluation (FAME) 1 (NCT00267774; 2009) and FAME 2 (NCT01132495; 2012), with inclusion of 2 years of follow-up data. The FAME 1 trial included patients with multivessel coronary artery disease from 20 medical centers in Europe and the United States. The FAME 2 trial included patients with stable coronary artery disease involving up to 3 vessels from 28 sites in Europe and North America. Lesions from the group in the FAME 1 trial from whom FFR was measured and the group in the FAME 2 trial who received FFR-guided PCI plus medical therapy were analyzed. Data analysis occurred from May 2017 to May 2018.

Interventions

Measure of post-PCI FFR.

Main Outcomes and Measures

Vessel-oriented clinical events at 2 years, a composite of cardiac death, target vessel-associated myocardial infarction, and target vessel revascularization.

Results

This analysis included 639 patients from whom pre-PCI and post-PCI FFR values were available. Of their 837 lesions, 277 were classified into the lowest tertile (ΔFFR≤0.18), 282 into the middle tertile (0.19≤ΔFFR≤0.31), and 278 into the highest tertile (ΔFFR>0.31). Vessel-oriented clinical events were significantly more frequent in the lowest tertile (n = 25 of 277 [9.1%]) compared with the highest tertile (n = 13 of 278 [4.7%]; hazard ratio, 2.01 [95% CI, 1.03-3.92]; P = .04). In addition, a significant association was observed between ΔFFR and symptomatic relief (odds ratio, 1.33 [95% CI, 1.02-1.74]; P = .02).

Conclusions and Relevance

In this analysis of 2 randomized clinical trials, the larger the improvement in FFR, the larger the symptomatic relief and the lower the event rate. This suggests that measuring FFR before and after PCI provides clinically useful information.

Management of Angina Post Percutaneous Coronary Intervention

PURPOSE OF REVIEW

Our review discusses the management of post percutaneous coronary intervention angina (PPCIA) which negatively impacts 20-40% of patients and imposes a high burden on the healthcare system.

RECENT FINDINGS

Mechanisms of PPCIA include microvascular dysfunction, distal coronary vasospasm or disease, microembolization, myocardial bridge, coronary artery disease (CAD) progression, and rarely stent thrombosis or in-stent restenosis. Nitrates, beta blockers (BB), calcium channel blockers, and ranolazine are the common medical management options. Only BB showed 1-year mortality benefit following myocardial infarction. Stress echocardiography and cardiac magnetic resonance are the best to detect CAD vs. microvascular dysfunction. Invasively, vasoprovocative testing and fractional flow reserve provide useful prognostic information. If the ischemia burden is ≤10%, conservative management should be considered based upon the individual patient scenario. The optimal management of PPCIA remains unclear and further research is necessary. Multiple treatment options exist, which should be implemented in an individualized fashion.

Comparison of Exercise Performance and Clinical Outcome Between Functional Complete and Incomplete Revascularization

Background and Objectives

Although percutaneous coronary intervention (PCI) is recommended to improve symptoms in patients with stable ischemic heart disease (SIHD), improvement of exercise performance is controversial. This study aimed to investigate changes in exercise duration after PCI according to functional completeness of revascularization by comparing pre- and post-PCI exercise stress test (EST).

Methods

Patients with SIHD were enrolled from a prospective PCI registry, and divided into 2 groups: 1) functional complete revascularization (CR) group had a positive EST before PCI and negative EST after PCI, 2) functional incomplete revascularization (IR) group had positive EST before and after PCI. Primary outcome was change in exercise duration after PCI and secondary outcome was major adverse cardiac events (MACE, a composite of any death, any myocardial infarction, and any ischemia-driven revascularization) at 3 years after PCI.

Results

A total of 256 patients (149 for CR group, and 107 for IR group) were eligible for analysis. Before PCI, exercise duration was not significantly different between the functional CR and IR groups (median 540 [interquartile range; IQR, 414, 602] vs. 480 [402, 589] seconds, p=0.091). After PCI, however, the CR group had a significantly higher increment of exercise duration than the IR group (median 62.0 [IQR, 12.0, 141.0] vs. 30.0 [−11.0, 103.5] seconds, p=0.011). The functional CR group also had a significantly lower risk of 3-year MACE (6.2% vs. 26.1%; adjusted hazard ratio, 0.19; 95% confidence interval, 0.09–0.41; p<0.001).

Conclusions

Functional CR showed a higher increment of exercise duration than functional IR.

Dobutamine Stress Echocardiography Ischemia as a Predictor of the Placebo-Controlled Efficacy of Percutaneous Coronary Intervention in Stable Coronary Artery Disease: The Stress Echocardiography-Stratified Analysis of ORBITA

BACKGROUND

Dobutamine stress echocardiography is widely used to test for ischemia in patients with stable coronary artery disease. In this analysis, we studied the ability of the prerandomization stress echocardiography score to predict the placebo-controlled efficacy of percutaneous coronary intervention (PCI) within the ORBITA trial (Objective Randomised Blinded Investigation With Optimal Medical Therapy of Angioplasty in Stable Angina).

METHODS

One hundred eighty-three patients underwent dobutamine stress echocardiography before randomization. The stress echocardiography score is broadly the number of segments abnormal at peak stress, with akinetic segments counting double and dyskinetic segments counting triple. The ability of prerandomization stress echocardiography to predict the placebo-controlled effect of PCI on response variables was tested by using regression modeling.

RESULTS

At prerandomization, the stress echocardiography score was 1.56±1.77 in the PCI arm (n=98) and 1.61±1.73 in the placebo arm (n=85). There was a detectable interaction between prerandomization stress echocardiography score and the effect of PCI on angina frequency score with a larger placebo-controlled effect in patients with the highest stress echocardiography score (P_interaction=0.031). With our sample size, we were unable to detect an interaction between stress echocardiography score and any other patient-reported response variables: freedom from angina (P_interaction=0.116), physical limitation (P_interaction=0.461), quality of life (P_interaction=0.689), EuroQOL 5 quality-of-life score (P_interaction=0.789), or between stress echocardiography score and physician-assessed Canadian Cardiovascular Society angina class (P_interaction=0.693), and treadmill exercise time (P_interaction=0.426).

CONCLUSIONS

The degree of ischemia assessed by dobutamine stress echocardiography predicts the placebo-controlled efficacy of PCI on patient-reported angina frequency. The greater the downstream stress echocardiography abnormality caused by a stenosis, the greater the reduction in symptoms from PCI.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT02062593.

Advances in Clinical Cardiology 2018: A Summary of Key Clinical Trials

INTRODUCTION

Many important clinical trials in cardiology were published or presented at major international meetings throughout 2018. This paper aims to offer a concise overview of these significant advances and to put them into clinical context.

METHODS

Trials presented at the major international cardiology meetings during 2018 were reviewed including The American College of Cardiology, EuroPCR, The European Society of Cardiology, PCR London Valves, Transcatheter Cardiovascular Therapeutics, and the American Heart Association. In addition to this a literature search identified several other publications eligible for inclusion based on their relevance to clinical cardiology, their potential impact on clinical practice and on future guidelines.

RESULTS

A total of 78 trials met the inclusion criteria. New interventional and structural data include trials examining novel stent designs (Biofreedom™, COMBO), use of drug-coated balloons in patients with high bleeding risk, intervention in stable coronary artery disease, revascularisation strategy in ST elevation myocardial infarction, transcatheter aortic valve replacement in low-risk patients, and percutaneous mitral or tricuspid valve interventions. Preventative cardiology data included the use of sodium glucose cotransporter-2 inhibitors (empagliflozin, dapagliflozin, canagliflozin), proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors (alirocumab) and approaches of hypertension management. Antiplatelet data included trials evaluating both the optimal length of course and combination of antiplatelet agents. Heart failure data included trials of sacubitril-valsartan during acute hospital admission and the management of chemotherapy-induced cardiotoxicity. Electrophysiology data included trials examining atrial fibrillation ablation, wearable cardiac defibrillators (LifeVest) and His-bundle pacing.

CONCLUSION

This article presents key clinical trials completed during 2018 and should be valuable to both cardiology clinicians and researchers.

Percutaneous coronary intervention for the management of stable ischemic heart disease

PURPOSE OF REVIEW

The purpose of this review is to summarize landmark studies and recent evidence in support for and against benefits of routine percutaneous coronary intervention (PCI) in the management of patients with stable ischemic heart disease (SIHD).

RECENT FINDINGS

Randomized controlled trials have raised uncertainty regarding the prognostic benefits of routine PCI in patients with SIHD. The benefits of PCI to improve symptoms and quality of life (QOL), thought to be more established, was brought into question recently by the ORBITA trial. Two hundred participants with single vessel SIHD optimized first on antianginal therapy were randomized to PCI or sham PCI procedure. At 6 weeks, there was no significant difference in the primary endpoint of exercise time increment (PCI minus sham PCI 16.6 s, 95% confidence interval -8.9 to 42.0 s, P = 0.20), or secondary endpoints of change in angina or QOL scores between the groups.

SUMMARY

Findings from this first placebo-controlled trial of PCI in patients with single vessel SIHD suggest that PCI need not necessarily be the first line or default strategy for symptomatic improvement. Results from the ongoing ISCHEMIA (International Study of Comparative Health Effectiveness with Medical and Invasive Approaches) trial will provide further guidance regarding symptomatic and prognostic benefits of early angiography and revascularization for higher risk SIHD patients with moderate-severe ischemia.

Association Between Physiological Stenosis Severity and Angina-Limited Exercise Time in Patients With Stable Coronary Artery Disease

Importance

Physiological stenosis assessment is recommended to guide percutaneous coronary intervention (PCI) in patients with stable angina.

Objective

To determine the association between all commonly used indices of physiological stenosis severity and angina-limited exercise time in patients with stable angina.

Design, Setting, and Participants

This cohort study included data (without follow-up) collected over 1 year from 2 cardiac hospitals. Selected patients with stable angina and physiologically severe single-vessel coronary artery disease presenting for clinically driven elective PCI were included.

Exposures

Fractional flow reserve (FFR), instantaneous wave-free ratio (iFR), hyperemic stenosis resistance (HSR), and coronary flow reserve (CFR) were measured invasively. Immediately after this, patients maximally exercised on a catheter-table-mounted supine ergometer until they developed rate-limiting angina. Subsequent PCI was performed in most patients, followed by repeat maximal supine exercise testing.

Main Outcomes and Measures

Associations between FFR, iFR, HSR, CFR, and angina-limited exercise time were assessed using linear regression and Pearson correlation coefficients. Additionally, the associations between the post-PCI increment in exercise time and baseline FFR, iFR, HSR, and CFR were assessed.

Results

Twenty-three patients (21 [91.3%] of whom were male; mean [SD] age, 60.6 [8.1] years) completed the pre-PCI component of the study protocol. Mean (SD) stenosis diameter was 74.6% (10.4%). Median (interquartile range [IQR]) values were 0.54 (0.44-0.72) for FFR, 0.53 (0.38-0.83) for iFR, 1.67 (0.84-3.16) for HSR, and 1.35 (1.11-1.63) for CFR. Mean (SD) angina-limited exercise time was 144 (77) seconds. Anatomical stenosis characteristics were not significantly associated with angina-limited exercise time. Conversely, FFR (R2 = 0.27; P = .01), iFR (R2 = 0.46; P < .001), HSR (R2 = 0.39; P < .01), and CFR (R2 = 0.16; P < .05) were all associated with angina-limited exercise time. Twenty-one patients (19 [90.5%] of whom were male; mean [SD] age, 60.1 [8.2] years) competed the full protocol of PCI, post-PCI physiological assessment, and post-PCI maximal exercise. After PCI, the median (IQR) FFR rose to 0.91 (0.85-0.96), median (IQR) iFR to 0.98 (0.94-0.99), and median (IQR) CFR to 2.73 (2.50-3.12), while the median (IQR) HSR fell to 0.16 (0.06-0.37) (P < .001 for all). The post-PCI increment in exercise time was most significantly associated with baseline iFR (R2 = 0.26; P = .02).

Conclusions and Relevance

In a selected group of patients with severe, single-vessel stable angina, FFR, iFR, HSR, and CFR were all modestly correlated with angina-limited exercise time to varying degrees. Notwithstanding the limited sample size, no clear association was demonstrated between anatomical stenosis severity and angina-limited exercise time.

Advances in Management of Stable Coronary Artery Disease: the Role of Revascularization?

PURPOSE OF REVIEW

Coronary artery disease remains the most common cause of death worldwide. In patients with biomarker-positive acute coronary syndrome, the combination of guideline-directed medical therapy with routine revascularization is associated with improved outcomes. However, the role of routine revascularization in stable ischemic heart disease, in addition to medical therapy, remains a matter of debate. In this review, we aimed to describe the role of revascularization in stable ischemic heart disease.

RECENT FINDINGS

Revascularization is indicated in patients with stable ischemic heart disease and progressive or refractory symptoms, despite medical management. When guided by ischemia presence, revascularization has failed to show survival benefit, compared with medical therapy alone in multiple clinical trials. On the other hand, revascularization guided by coronary lesion severity, assessed by FFR or iFR, has been shown to offer survival benefit and improvement in symptom severity. PCI-revascularization of unprotected left main disease is feasible with comparable to surgical approach outcomes. Clinical decision to perform revascularization in stable ischemic heart disease necessitates a heart team approach, and no simple algorithm can guide this process. Further studies are required to assess the benefit of routine revascularization, in combination to medical therapy, in this population.

Coronary Physiology in the Cardiac Catheterization Laboratory

Coronary angiography has been the principle modality for assessing the severity of atherosclerotic coronary artery disease for several decades. However, there is a complex relationship between angiographic coronary stenosis and the presence or absence of myocardial ischemia. Recent technological advances now allow for the assessment of coronary physiology in the catheterization laboratory at the time of diagnostic coronary angiography. Early studies focused on coronary flow reserve (CFR) but more recent work has demonstrated the physiologic accuracy and prognostic value of the fractional flow reserve (FFR) and instantaneous wave free ratio (iFR) for the assessment of coronary artery disease. These measurements have been validated in large multi-center clinical trials and have become indispensable tools for guiding revascularization in the cardiac catheterization laboratory. The physiological assessment of chest pain in the absence of epicardial coronary artery disease involves coronary thermodilution to obtain the index of microcirculatory resistance (IMR) or Doppler velocity measurement to determine the coronary flow velocity reserve (CFVR). Physiology-based coronary artery assessment brings "personalized medicine" to the catheterization laboratory and allows cardiologists and referring providers to make decisions based on objective findings and evidence-based treatment algorithms. The purpose of this review is to describe the theory, technical aspects, and relevant clinical trials related to coronary physiology assessment for an intended audience of general medical practitioners.

Systemic microvascular dysfunction in microvascular and vasospastic angina

Aims

Coronary microvascular dysfunction and/or vasospasm are potential causes of ischaemia in patients with no obstructive coronary artery disease (INOCA). We tested the hypothesis that these patients also have functional abnormalities in peripheral small arteries.

Methods and results

Patients were prospectively enrolled and categorised as having microvascular angina (MVA), vasospastic angina (VSA) or normal control based on invasive coronary artery function tests incorporating probes of endothelial and endothelial-independent function (acetylcholine and adenosine). Gluteal biopsies of subcutaneous fat were performed in 81 subjects (62 years, 69% female, 59 MVA, 11 VSA, and 11 controls). Resistance arteries were dissected enabling study using wire myography. Maximum relaxation to ACh (endothelial function) was reduced in MVA vs. controls [median 77.6 vs. 98.7%; 95% confidence interval (CI) of difference 2.3-38%; P = 0.0047]. Endothelium-independent relaxation [sodium nitroprusside (SNP)] was similar between all groups. The maximum contractile response to endothelin-1 (ET-1) was greater in MVA (median 121%) vs. controls (100%; 95% CI of median difference 4.7-45%, P = 0.015). Response to the thromboxane agonist, U46619, was also greater in MVA (143%) vs. controls (109%; 95% CI of difference 13-57%, P = 0.003). Patients with VSA had similar abnormal patterns of peripheral vascular reactivity including reduced maximum relaxation to ACh (median 79.0% vs. 98.7%; P = 0.03) and increased response to constrictor agonists including ET-1 (median 125% vs. 100%; P = 0.02). In all groups, resistance arteries were ≈50-fold more sensitive to the constrictor effects of ET-1 compared with U46619.

Conclusions

Systemic microvascular abnormalities are common in patients with MVA and VSA. These mechanisms may involve ET-1 and were characterized by endothelial dysfunction and enhanced vasoconstriction.

Clinical trial registration

ClinicalTrials.gov registration is NCT03193294.

Percutaneous coronary intervention for stable coronary artery disease

The adverse consequences of stable coronary artery disease (CAD) are death, myocardial infarction (MI) and angina. Trials in stable CAD show that percutaneous coronary intervention (PCI) does not reduce mortality. PCI does appear to reduce spontaneous MI rates but at the expense of causing some periprocedural MI. Therefore, the main purpose of PCI is to relieve angina. Indeed, patients and physicians often choose PCI rather than first attempting to control symptoms with anti-anginal medications as recommended by guidelines. Nevertheless, it is unclear how effective PCI is at relieving angina. This is because, whereas anti-anginal medications are universally required to be tested against placebo, there is no such requirement for procedural interventions such as PCI. The first placebo-controlled trial of PCI showed a surprisingly small effect size. This may be because it is overly simplistic to assume that the presence of a stenosis and inducible ischaemia in a patient means that the clinical chest pain they report is caused by ischaemia. In this article, we review the evidence base and argue that if we as a medical specialty wish to lead the science of procedures for symptom control, we should recognise the special merit of placebo-controlled experiments.

A systematic review and critical analysis of cost-effectiveness studies for coronary artery disease treatment

Background: Cardiovascular disease remains the primary cause of death among Australians, despite dramatic improvements in overall cardiovascular health since the 1980s. Treating cardiovascular disease continues to place a significant economic strain on the Australian health care system, with direct healthcare costs exceeding those of any other disease. Coronary artery disease accounts for nearly one third of these costs and spending continues to rise. A range of treatments is available for coronary artery disease yet evidence of cost-effectiveness is missing, particularly for the Australian context. Cost-effectiveness evidence can signal waste and inefficiency and so is essential for an efficient allocation of healthcare resources. Methods: We used systematic review methods to search the literature across several electronic databases for economic evaluations of treatments for stable coronary artery disease.  We critically appraised the literature found in searches, both against the CHEERS statement for quality reporting of economic evaluations and in terms of its usefulness for policy and decision-makers. Results: We retrieved a total of 308 references, 229 once duplicates were removed. Of these, 26 were excluded as they were not full papers (letters, editorials etc.), 55 were review papers, 50 were not cost-effectiveness analyses and 93 related to a highly specific patient sub-group or did not consider all treatment options.  This left five papers to be reviewed in full. Conclusions: The current cost-effectiveness evidence does not support the increased use of PCI that has been seen in Australia and internationally. Due to problems with accessibility, clarity and relevance to policy and decision-makers, some otherwise very scientifically rigorous analyses have failed to generate any policy changes.