Which Parameter Should Be Chosen as Primary Endpoint for Randomized Drug-Eluting Stent Studies?

Appropriate Surrogate Endpoint in Drug-Coated Balloon Trials for Coronary Artery Diseases

Background

The appropriateness of using late lumen loss (LLL) as a surrogate endpoint was established in drug-eluting stent (DES) studies, but it was less supportive for drug-coated balloon (DCB) trials.

Methods

Studies published until 23 June 2021 were searched from PubMed, EMBASE, Cochrane Library, and ClinicalTrials.gov. The correlation between LLL, MLD (minimal lumen diameter), and %DS (percentage diameter stenosis) and clinical endpoints was evaluated by linear regression. Standardized effect size and its 95% CIs were used to illustrate the difference among LLL, MLD, and %DS.

Results

A total of 24 clinical trials were eligible [16 DCB vs. DES, 7 DCB vs. plain old balloon angioplasty (POBA), and 1 DCB vs. DES vs. POBA]. Thirteen (54.2%) trials used LLL as the primary endpoint. LLL, MLD, and %DS all had significant associations with clinical endpoints. For DCB vs. DES trials, the number of studies that reported inconsistent results between LLL and MLD was 12/16 (75.0%) and between LLL and %DS was 10/15 (66.7%), while in MLD and %DS, it was 1/16 (6.3%). The difference of standardized effect size between LLL and MLD was −0.47 (95% CI, −0.69 to −0.25, p < 0.001) and LLL and %DS was−0.31 (95%CI,−0.43 to−0.20, p < 0.001) while in MLD and %DS, there was no difference, 0.1 (95%CI,−0.02 to 0.22, p = 0.084).

Conclusions

For DCB trials, an appropriate surrogate is associated with the control device. The traditional LLL could be used in the DCB vs. POBA trials. However, MLD/%DS should be considered a more suitable surrogate endpoint when comparing DCB with DES.

A New and Rapid Scoring System to Assess the Scientific Evidence from Clinical Trials

Guidelines are based on a scientific analysis from existing data of randomized controlled trials (RCTs), registry trials, simple registries, case reports, and the personal experience of the task force members. Furthermore, meta-analyses and subgroup analyses are used to derive the strengths of recommendations. Fortunately, the major cardiac societies, i.e., the American College of Cardiology (ACC), the American Heart Association (AHA), and the European Society of Cardiology (ESC), are essentially using the same definitions for the levels of recommendations. In the expanding field of cardiology, however, the overwhelming and increasing number of clinical studies reveals the limitations of the traditional ranking of these studies: Applying the standard definitions of the ACC/AHA/ESC criteria for the levels of recommendation, almost every PCI procedure would easily reach the level of evidence A, even with two small, underpowered studies and a surrogate endpoint. Although meta-analyses are important tools for creating an overview of major diagnostic or treatment modalities, they are bound to severe limitations. The compilation of several underpowered, small trials can generate a statistically artificial "significant" result. This is especially important because only two meta-analyses containing almost identical studies could easily yield an evidence level A. RCTs are usually designed and conducted according to a power calculation, for which a primary clinical or surrogate endpoint can be chosen. Surrogate endpoints, however, do not necessarily correlate with the clinical outcome. The history of medicine is full of errors introduced by underpowered studies with surrogate endpoints. Many investigators and companies attempt to tease out treatment effects in specific subpopulations of patients. These subgroup analyses are usually underpowered. Another major limitation of the ACC/AHA/ESC scoring system is that neither the power of a study nor the choice of a primary clinical endpoint is included in their definitions. Yet another limitation of the ACC/AHA/ESC grading system is that two "simple" registries may already lead to a level of evidence B. A new scoring system is presented addressing most of these limitations: a primary clinical endpoint receives three points, whereas all of the following receive one point: double-blind design, evaluation interval of primary endpoint > or = 6 months, multicenter (at least three centers), independent data and safety monitoring, power of > or = 80% for primary endpoint achieved, and follow-up > or = 80% for a surrogate primary endpoint or follow-up of > or = 95% for a clinical primary endpoint. Thus, the maximum achievable points is 10. This scoring system can also be applied for high-quality registry controlled trials using a predefined control group and power calculation. For simple registry studies and subgroup analyses, a modified scoring system has been developed (maximum achievable points is 5). The advantage of the suggested new scoring system is its transparency, reproducibility, and ease of use by quickly answering the key quality questions for clinical trials. The new scoring system suggested here should help make decisions regarding which treatment to use and stimulate discussions.

Guidelines for percutaneous coronary interventions. The Task Force for Percutaneous Coronary Interventions of the European Society of Cardiology

In patients with stable CAD, PCI can be considered a valuable initial mode of revascularization in all patients with objective large ischaemia in the presence of almost every lesion subset, with only one exception: chronic total occlusions that cannot be crossed. In early studies, there was a small survival advantage with CABG surgery compared with PCI without stenting. The addition of stents and newer adjunctive medications improved the outcome for PCI. The decision to recommend PCI or CABG surgery will be guided by technical improvements in cardiology or surgery, local expertise, and patients' preference. However, until proved otherwise, PCI should be used only with reservation in diabetics with multi-vessel disease and in patients with unprotected left main stenosis. The use of drug-eluting stents might change this situation. Patients presenting with NSTE-ACS (UA or NSTEMI) have to be stratified first for their risk of acute thrombotic complications. A clear benefit from early angiography (<48 h) and, when needed, PCI or CABG surgery has been reported only in the high-risk groups. Deferral of intervention does not improve outcome. Routine stenting is recommended on the basis of the predictability of the result and its immediate safety. In patients with STEMI, primary PCI should be the treatment of choice in patients presenting in a hospital with PCI facility and an experienced team. Patients with contra-indications to thrombolysis should be immediately transferred for primary PCI, because this might be their only chance for quickly opening the coronary artery. In cardiogenic shock, emergency PCI for complete revascularization may be life-saving and should be considered at an early stage. Compared with thrombolysis, randomized trials that transferred the patients for primary PCI to a 'heart attack centre' observed a better clinical outcome, despite transport times leading to a significantly longer delay between randomization and start of the treatment. The superiority of primary PCI over thrombolysis seems to be especially clinically relevant for the time interval between 3 and 12 h after onset of chest pain or other symptoms on the basis of its superior preservation of myocardium. Furthermore, with increasing time to presentation, major-adverse-cardiac-event rates increase after thrombolysis, but appear to remain relatively stable after primary PCI. Within the first 3 h after onset of chest pain or other symptoms, both reperfusion strategies seem equally effective in reducing infarct size and mortality. Therefore, thrombolysis is still a viable alternative to primary PCI, if it can be delivered within 3 h after onset of chest pain or other symptoms. Primary PCI compared with thrombolysis significantly reduced stroke. Overall, we prefer primary PCI over thrombolysis in the first 3 h of chest pain to prevent stroke, and in patients presenting 3-12 h after the onset of chest pain, to salvage myocardium and also to prevent stroke. At the moment, there is no evidence to recommend facilitated PCI. Rescue PCI is recommended, if thrombolysis failed within 45-60 min after starting the administration. After successful thrombolysis, the use of routine coronary angiography within 24 h and PCI, if applicable, is recommended even in asymptomatic patients without demonstrable ischaemia to improve patients' outcome. If a PCI centre is not available within 24 h, patients who have received successful thrombolysis with evidence of spontaneous or inducible ischaemia before discharge should be referred to coronary angiography and revascularized accordingly--independent of 'maximal' medical therapy.