Zero-Contrast PCI in CKD Patients Helps Avoid Later Dialysis

SAN FRANCISCO — For a technique that relies heavily on intravascular imaging to guide coronary stenting in patients with chronic kidney disease (CKD), there's no contrast.

Avoidance of contrast-induced nephropathy (CIN) is important with any percutaneous coronary intervention (PCI), but the way to avoid it with certainty — and to make PCI safer in patients already with renal disease — would be not to use contrast agent at all.

That's exactly what researchers reporting here at Transcatheter Cardiovascular Therapeutics (TCT) 2019 achieved by taking advantage of intravascular ultrasound (IVUS) and physiologic measurements to guide coronary stenting and make angiograms unnecessary.

Later need for dialysis fell off sharply in their cohort of 82 patients with CKD, a group often passed over for PCI due to risk of further kidney damage, who underwent the procedure using "zero contrast" techniques.

Separately in a small randomized comparison, the group also saw a significantly reduced risk of CIN and need for dialysis in patients with CKD who underwent diagnostic angiography using no more than a thimbleful or two of contrast agent, usually 10 mL or less.

"Our early data suggest that zero-contrast PCI can potentially significantly reduce the incidence of dialysis in patients with advanced CKD who require invasive angiography and coronary intervention," and who have "a wide variety of lesion types and complexity," Hussein M. Rahim, MD, Columbia University, New York City, said when presenting the results.

Patients in the zero-contrast PCI series had all received a small amount of contrast for diagnostic angiography, an average of 15 mL. Their subsequent PCI was performed at the same session in 18% of cases and staged in the remaining 82% an average of 22 days later.

A few patients, 28% of the cohort, required a small amount of contrast agent during the stenting procedure, a mean of 1.3 mL. But 99% of PCIs were completed with less than 10 mL of contrast, and PCI was entirely contrast-free in 72%.

"We're not fanatics about this. If the patient is having unrelenting chest pain and electrocardiographic changes, you obviously need to take a contrast injection," Rahim said. "But what we're showing here is that in the vast majority of these cases, when done carefully, we don't need to."

Patients With the Most to Gain

About 40% of patients with a clinical indication for diagnostic angiography don't actually get one, often over fear of CIN and hastened need for dialysis in patients with compromised renal function, Ziad A. Ali, MD, DPhil, New York-Presbyterian Hospital, New York City, told theheart.org | Medscape Cardiology.

"Most of these patients are not getting revascularization, and these are patients that stand the most to benefit, potentially, from PCI," said Ali, who is senior author on the zero-contrast PCI and low-contrast diagnostic angiography studies.

"One of the take-homes from this is that you don't have to do zero in order to protect the patient. You can use 10 mL, but it's certainly better than using 100 mL," he said.

The zero-contrast PCI technique seems a "very important" development for the field, Donald Cutlip, MD, Beth Israel Deaconess Medical Center, Boston, Massachusetts, told theheart.org | Medscape Cardiology.

"I think we'll all be a little nervous walking away from the cath-lab table without that final picture. But if the patient's doing well, and with the knowledge you're saving the kidneys, I think it’s a valuable asset," said Cutlip, who is not associated with the two reports.

"I don't think it's a large number of these CKD patients that we're turning away from PCI, but I think we're not doing it as safely as we can. And we're certainly causing contrast-induced nephropathy, and that leads to a lot of bad outcomes, including mortality. So I think the real key is that it'll be a safer procedure."

Ali said his group "started out conservatively" and selected patients with simple lesions when they performed their first zero-contrast PCI procedures in 2015. "But as we developed experience, we didn't turn down anybody. We do atherectomy, we do bifurcations, we do left-main disease, we do basically everything."

Mean lesion length in the current series was 30 mm; 16% of the procedures involved atherectomy, 6% were left-mains, 5% were bypass-graft interventions, 3% were chronic total occlusions, and 3% involved hemodynamic support. All procedures were technical successes.

Operator experience is important to case selection, Ali noted. "You have to have a proficient understanding, almost to the point of expertise, of using intravascular ultrasound. You need to be proficient, at least, in being able to do physiology," he said, referring to use of an intracoronary pressure-wire to assess the impact of lesions on flow.

How to Do Zero-Contrast PCI

As Rahim described, the strategy starts with "ultra-low-contrast" angiography (ULCA) followed by PCI, both of which call for various established but not routinely used equipment and methods for minimizing or avoiding use of contrast agent.

They include small-diameter catheters without side holes, and avoidance of "puffing," the occasional squirts of dye operators may use on-the-go to help them orient the catheter. Multiple angiograms to check progress are avoided, and contrast agent is removed during catheter exchanges, he said.

In the current series, a pressure-wire assessed flow reserve in 11% of patients to confirm or rule out whether a given location should be stented.

IVUS is used liberally to guide catheter placement, including afterwards to check for any stent underexpansion, dissection, or intramural hematoma, Rahim said.

A total of 99 zero-contrast PCI procedures were performed from 2015 to 2018 in the prospective series of 82 patients with stage 4 to 5 CKD; their mean age was 64.6 years, 68% had diabetes, and 40% received the intervention for acute coronary syndrome.

PCI was with radial-artery access in 34% of cases; fluoroscopy time averaged 25 minutes, and the mean radiation dose was 1.1 Gy. Three-fourths received stents for a single lesion. The only complication thought related to the procedure was a wire perforation in one patient, which was managed with pericardiocentesis.

Over a mean follow-up of 328 days, 21% of patients required renal-replacement therapy, including three patients who started it within 30 days of the procedure.

That compares to a 48.3% 1-year rate of dialysis in a cohort of similar patients with CKD who underwent diagnostic angiography using conventional methods, without PCI, who received an average of about 40 mL of contrast agent. The hazard ratio (HR) for dialysis in the zero-contrast cohort was 0.40 (95% CI, 0.21 - 0.75; P = .0032), Rahim reported.

Diagnostic Cases, A Randomized Trial

Also on Ali's research team, Navdeep K. Bhatti, MD, Montefiore Medical Center, Bronx, New York, presented a single-center comparison of 101 patients with CKD stage 4 to 5 and clinical indications for coronary angiography who were randomly assigned to ULCA or "conventional low-dose, contrast-restricted coronary angiography."

The 51 and 50 patients, respectively, were similar at baseline for demographics, comorbidities, cardiovascular history, smoking status, medications, and renal laboratory markers. They received pre- and post-procedure hydration according to the same protocol.

"ULCA was safe and feasible without accelerating a decline in renal function" and was associated with less CIN and need for later dialysis compared with the conventional low-dose approach, Bhatti said.

The ULCA procedures used an average 13.5 mL of contrast, compared with 39.9 mL in the conventional group (P < .0001). None of the ULCA patients and four in the other group developed CIN, and none and four, respectively, required renal-replacement therapy soon after the procedure (P = .04 for both).

Over the next 2 years, 34.5% of ULCA patients and 59.5% of those in the conventional group required dialysis, for an HR of 0.39 (95% CI, 0.20 - 0.75; P = .003).

Multivariate analysis identified several independent predictors of freedom from renal-replacement therapy, including ULCA, HR 0.40 (95% CI, 0.18 - 0.86; P = .02); pre-procedure estimated glomerular filtration rate, HR 0.91 (95% CI, 0.86 - 0.96; P =.003); and left ventricular ejection fraction, HR 0.97 (95% CI, 0.95 - 0.99; P = .003).

"Zero-contrast PCI is a leap forward," Cutlip said. But the purely diagnostic ULCA procedure that minimizes contrast agent uses techniques that "I think we're all trying to do," he observed.

"What's new is that they protocolized it. They determined what images they were going to take and had a plan for when they didn't get diagnostic quality," he said.

Ali has reported receiving personal fees and equity in Shockwave Medical; grants from Cardiovascular Systems and Abbott Vascular; and personal fees from Boston Scientific, AstraZeneca, ACIST Medical, Opsens Medical, and Cardinal Health "outside the submitted work." Rahim, Cutlip, and Bhatti have reported no relevant financial relationships.

Transcatheter Cardiovascular Therapeutics 2019: Abstracts TCT 30 and TCT 32. Presented September 25, 2019.

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