Traditional Cath Lab Practices Scrutinized, Some Debunked, in AHA Statement

Some of the things that are regularly done in the cardiac cath lab lack solid supporting evidence and probably shouldn’t be done anymore, according to a new scientific statement from the American Heart Association.

“Although some practices have emerged based on evidence, many traditions have persisted based on beliefs and theoretical concerns,” a writing group chaired by Sripal Bangalore, MD (NYU School of Medicine, New York, NY), says in introducing the document.

The aim of the review, published online June 30, 2021, ahead of print in Circulation, “is to highlight common preprocedure, intraprocedure, and postprocedure catheterization laboratory practices where evidence has accumulated over the past few decades to support or discount traditionally held practices.”

Bangalore told TCTMD the statement is meant to be complementary to other guidance on best practices in the cath lab—like that from the Society for Cardiovascular Angiography and Interventions, which was most recently updated in April 2021. The current document delves deeper into practices for which there isn’t universal agreement but for which some evidence has accumulated over the past few decades, detailing the thought process behind them. That’s something more-comprehensive guidance generally can’t do. “I felt like there was this gap we need to address,” Bangalore said.

Before Procedures

The authors start by tackling the common practice of requiring patients to have nothing by mouth—also called nil per os, or NPO—past midnight or for several hours before an invasive procedure. They found little evidence to support an extended fast, and point to guidelines from the American Society of Anesthesiologists for a different recommendation—clear liquids are allowed up to 2 hours before and a light meal up to 6 hours before a procedure. Further research, Bangalore et al say, is needed to determine whether a strategy using no fasting is better than that.

“Nothing by mouth should be at the discretion of the interventionalist and may not be necessary for patients who undergo procedures with only local anesthesia and no sedation, in which upper airway protective reflexes are not impaired and no risk factors for pulmonary aspiration are present,” the authors write.

The document also examines practices around the withholding of medications like metformin, other glucose-lowering agents, renin-angiotensin-aldosterone blockers, and oral anticoagulants before procedures; steroid premedication; and management of patients with shellfish allergies, who “are considered at high risk of having an allergic reaction to iodinated contrast media and are often pretreated to prevent allergic reactions.”

The writing group concludes, however, that “patients with a history of shellfish allergy alone do not need premedication before undergoing cardiac catheterization. In patients with a previous moderate or severe acute reaction to contrast media, premedication prophylaxis for an allergic reaction is recommended.”

During and After Procedures

Intraprocedural issues examined by Bangalore et al include the use of combinations of benzodiazepines and opioids for sedation, considerations around patients with a nickel allergy, and several practices revolving around vascular access. Those include the avoidance of transradial access in patients with prior mastectomy; the routine performance of Allen or Barbeau tests to assess radial and ulnar patency prior to using radial access; transradial access in patients requiring CABG surgery or dialysis; and safe femoral access techniques.

Of note, after reviewing the evidence, the authors conclude that tests of collateral circulation to the hand are not useful for assessing the safety of transradial access and also that ipsilateral transradial access can be performed with low risks of infection or other complications in patients with prior mastectomy.

And finally, in the postprocedural phase, the document details evidence around the practice of avoiding nonemergency MRIs for 4 to 6 weeks after stent implantation out of concerns for device migration and heating and tissue damage.

That’s not necessary, Bangalore et al indicate: “Current consensus maintains that recent coronary stent implantation is not a contraindication to MRI. There are no published reports of adverse events associated with performing MRI in a patient following commercially available coronary stent implantation.”

Bangalore told TCTMD, “I think this is going to be somewhat practice-changing,” because it will allow clinicians to examine the evidence behind some of the things they’ve been doing in the cath lab without understanding the rationale. That will “hopefully change some of the practices” that are not well supported by evidence, he added.

People have expressed excitement about the document in the short time it’s been out, Bangalore said. He pointed to reactions on Twitter, came from Andrew Sharp, MBChB, MD (University Hospital of Wales, Cardiff). Sharp said the paper is “one of the most useful documents I’ve read in a while, providing practical advice to every cath lab in the land. This could save millions of pounds in wasted archaic practices.”