Time to Debunk Ingrained Practices in the Catheterization Laboratory

From the introduction of diagnostic cardiac catheterization by Andre Cournand and Dickinson Richards in the early 1940s, to the first human transcatheter aortic valve replacement in the 2000s, the evolution of cardiac procedures spans several decades of significant groundbreaking achievements. As a result, the breadth of cardiac catheterization procedures has rapidly expanded in scope, and over a million procedures are performed yearly in the United States.¹ Although some practices have emerged based on evidence, many others have been adopted based on theoretical concerns or beliefs. The Society for Cardiovascular Angiography and Interventions (SCAI) expert consensus statements released in 2012 and 2016 to provide best practices in the cardiac catheterization laboratory have been very well received by the “Interventional Community”.² In this scientific statement, Bangalore and colleagues outline the supporting data or lack thereof for common practices for which there is no universal agreement but have been followed for decades.³

Several pre, intra, and post-procedure practices are discussed in detail in the document. Provided for each practice is a breakdown of the rationale, the evidence available, and a summary of recommendations based on the existing data. Some of the addressed pre-procedure evidence-based practices are related to the duration of Nil Per Ora (NPO), discontinuation of medications, and pre-medication for patients allergic to contrast media. Intra-procedure evidence-based practices include sedation, analgesia, vascular access, and the treatment of metal allergy. Lastly, post-procedure evidence-based practices discuss MRI use in patients with newly implanted coronary stents.

The rationale for prolonged fasting (>12 hours) before cardiac catheterization procedures is to minimize the risk of pulmonary aspiration in case of emesis in a state of decreased consciousness or emergent need for induction of general anesthesia for intubation. However, the evidence to support prolonged NPO is limited. The CHOW-NOW trial showed non-inferiority of a non-fasting strategy compared to standard fasting preparation with respect to a composite primary outcome of contrast-induced nephropathy, peri-procedural hypotension, aspiration pneumonia, emesis, and hypoglycemia.⁴ Moreover, the incidence of emesis with current contrast agents and the need for emergent intubation is exceedingly rare. Going beyond existing recommendations from the American Society of Anesthesiologist (ASA) for shorter fasting times of up to 2 and 6 hours before the procedure for clear liquids and light meal, respectively The AHA Scientific Statement advocates that NPO duration should be at the discretion of the interventionalist and may not be necessary if only local anesthesia without sedation is used.

The AHA Scientific Statement also addresses the pre-procedural management of some medications that could affect the procedure or its outcome. Contrary to the current practice of holding medications like metformin or Renin-Angiotensin System (RAS) inhibitors pre-procedurally, this document suggests new practices. As examples, they propose the avoidance of metformin only in patients with moderate or severe renal impairment, holding RAS inhibitors in patients with renal dysfunction (eGRF < 60 ml/min), and do not hold glucose-lowering medications before the procedure. The authors also highlight the lack of data regarding newer agents (e.g., SGLT-2 inhibitors) and reduced insulin dose. An area of more controversy is interrupting oral anticoagulation (OAC) before cardiac catheterization procedures. Heterogeneous data has not shown a significant difference in major complications between interrupted and uninterrupted OAC. Extrapolating from the BRIDGE trial, interruption of OAC for five days before elective surgery was non-inferior to bridging with low molecular weight heparin (LMWH) and resulted in less bleeding.⁵ The decision to interrupt OAC should be based on the patient's thrombotic risk, the bleeding risk associated with the type of procedure, and vascular access site; the risk for bleeding should be weighed against the risk for thrombotic events. In patients with elevated thrombotic risk (e.g., mechanical valves, atrial fibrillation, and history of stroke), OAC should be continued, especially if the procedure can be performed via the transradial (TR) route. Conversely, in patients with elevated bleeding and low thrombotic risks, OAC should be withheld. The document provides the optimal timing for withholding OAC for different agents based on renal function; however, for patients on warfarin, it does not suggest a target INR considered safer to perform the procedure. Different operators have varying thresholds but would not cancel a diagnostic procedure with INR < 3.5 or an interventional procedure with INR < 3.0.

A lengthy segment of Statement addresses the choice of vascular access. TR access reduces major bleeding and vascular complications and may also reduce mortality in selected patients compared to transfemoral TF access.⁶ The adoption of TR access for cardiac catheterization procedures has grown significantly and became the default approach for many operators. This document emphasizes the use of TR access with appropriate techniques, including in patients with prior mastectomy. Avoidance of TR access in these patients appears to be based on a myth rather than facts. However, it does recommend considering alternative access (e.g., distal radial artery, ulnar artery, femoral artery) in patients who may need CABG or dialysis.

When TF access is considered, the implementation of safe practices can minimize the risk of bleeding and vascular complications. Careful assessment of history of peripheral arterial disease, review of previous femoral angiograms when available, use of ultrasound guidance, fluoroscopic landmarks, along with a micropuncture needle are all considered best practices for TF access. Ultrasound guidance not only allows identifying the common femoral artery bifurcation but also avoiding segments with stenosis or calcification. Randomized data showed decreased vascular complications, access-site hematomas, number of attempts and time to access as well as increased success rate of the first attempt when using ultrasound guidance.⁷ Even though there is no randomized evidence supporting the use of micropuncture needle versus a standard 18-gauge needle, current practice has significantly shifted towards the use of micropuncture needle that confers a smaller arteriotomy and potentially reduce the risk of bleeding.

In summary, this AHA Scientific Statement is a laudable effort to debunk catheterization laboratory myths and old ingrained practices that are not based on evidence but on theoretical concerns. The document is very well structured and provides answers to many of the “questions we always wanted to know about the catheterization laboratory but were afraid to ask”. It is complementary to the SCAI Best Practices, an excellent primer for cardiology fellows, and will hopefully help streamline the care of patients undergoing catheterization procedures. There are still areas lacking conclusive evidence, and hopefully, this statement will stimulate further research that will allow science catch up with practice. As cardiac catheterization continues to evolve and expand in scope, the adoption of practices based on evidence and not on myths, will lead to practices that are in the best interests of the patient.