As PCI Case Volume Drops, Mortality Edges Up—but How Much Does It Matter?

Fran Lowry

June 12, 2017

DURHAM, NC — A huge proportion of PCI operators in the US do fewer than the guideline-recommended threshold of 50 cases a year, and in-hospital mortality for those cases is slightly higher than for operators with higher annual case volumes, according to an analysis based on National Cardiovascular Data Registry (NCDR) numbers from 2009 to 2015[1].

The low-volume operators often worked at low-volume hospitals and tended to do more emergency PCIs, including primary PCI for STEMI, according to a report published in the June 20, 2017 issue of Journal of the American College of Cardiology.

"Almost half of PCI operators, 44%, do fewer than the recommended 50 procedures a year. These low-volume operators do many procedures for emergencies, and they may be filling a key role in maintaining access to PCI," lead author Dr Alexander C Fanaroff (Duke University, Durham, NC), told heartwire from Medscape.

An accompanying editorial agrees and goes further[2]. Low-volume operators and hospitals in rural areas are less likely to reach 50 PCI annually, but they still provide important services such as primary PCI for STEMI, write Dr Dharam J Kumbhani (University of Texas Southwestern Medical Center, Dallas) and Dr Brahmajee K Nallamothu (University of Michigan, Ann Arbor).

"Even as we push for more appropriate use of technology and procedures, the arithmomania around volume thresholds could perversely incentivize interventional cardiologists to do less appropriate cases to reach an arbitrary target that keeps their privileges active and their cath labs open," they write.

It is time to seriously rethink "our obsession with volume benchmarks, a metric that we have assiduously clung to for the past several decades. Volume may be among the factors, but it should be considered only under a quality-assessment program that is more comprehensive."

In 2013, observe Fanaroff and colleagues, the American College of Cardiology (ACC)/American Heart Association (AHA)/Society for Cardiovascular Angiography and Intervention(SCAI) clinical competence statement reduced the recommended minimum annual number of PCI procedures per operator from 75 to 50, averaged over 2 years.

The researchers looked at outcomes related to operator case-volume in the NCDR CathPCI registry in a period that included the new recommendation, from July 1, 2009 to March 31, 2015. The registry includes all cath labs in the US except VA and military. The current analysis involves more than 3.7 million PCI procedures performed by 10,496 operators at 1584 sites.

Of the total group of operators, 4628 (44%) performed <50 PCIs per year; 3001 (29%) performed 50 to 100 PCIs per year, and 2867 (27%) performed >100 PCIs per year.

The median annual PCI case volume was 59 PCIs (interquartile range [IQR] 21–106).

Operator volumes varied by region, with those in the Western US having the lowest annual volumes, followed by operators from the South, Midwest, and North. Median volume varied from a low of 33 in Nevada to a high of 142 in Rhode Island. Alaska had the fewest operators (n=9), and California had the most operators (n=1197).

PCIs performed by low-volume operators were more often in patients with STEMI than those performed by intermediate- or high-volume operators (20.7% vs 19.0% vs 15.1%; P<0.0001) and were more often other urgent or emergent PCI (22.6% vs 20.7% vs 16.6%; P<0.001).

Overall, 59,400 patients (1.6%) died in the hospital. Operator volume was linearly and inversely associated with in-hospital mortality. For every 50-case decrease in annual PCI volume, there was a corresponding 4% increase in in-hospital mortality (odds ratio [OR] 1.04; 95% CI 1.03–1.05).

That was after adjustment for variables in the Cath PCI Mortality Model (age, cardiogenic shock, prior heart failure, peripheral vascular disease, chronic lung disease, estimated glomerular filtration rate, NYHA functional class, presentation with STEMI vs no STEMI).

In-hospital mortality for high-volume operators was 1.53%, for intermediate-volume operators it was 1.73%, and for low-volume operators, it was 1.86%.

"The absolute difference in outcomes is small. If you had to take those numbers and turn them into the number needed to treat, you would have to move something like 700 PCIs from intermediate to high and 250 PCIs from low to high to actually save one life. So, the differences are really small, and I think that is important to stress," Dr Fanaroff said.

The learning curve with PCI that was first reported in 1984 was the beginning of PCI arithmomania, or obsession with numbers, according to editorialists Kumbhani and Nallamothu. This led to the belief that operators who performed more PCIs were better.

"This made sense in the early days: the procedure was still in its infancy, and few operators were formally trained. Given the intuitive appeal that experience should matter and the ease of collection and reporting volume data, policy makers and third-party payers aggressively endorsed PCI volume minimums as a surrogate for quality of care," they write.

But procedures mature over time and the volume-outcome relationship may change with new technology and approaches, they propose. PCI performed currently is fundamentally different from PCI in the angioplasty era: the procedure is more complex and variable.

"In fact, given the wide breadth of approaches, it is almost absurd to lump all procedures together under a simplistic rubric of 'PCI' when assessing volume. Is PCI of 50 type A lesions comparable to that of 50 chronic-total-occlusion PCI?"

Certainly not, they contend. "The practice of interventional cardiology in 2017 looks very different from its inception in 1977, and it is high time that quality assessment is updated from 1977 to 2017 as well."

The study was funded by the National Cardiovascular Data Registry. Fanaroff reports that he has received funding from Gilead Science. Disclosures for the coauthors are listed in the paper. Kumbhani has received honoraria and research support from the American College of Cardiology and consulting fees from Aralez and Somahlutions. Nallamothu has received honoraria from the American Heart Association.

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