When to Call the Cath Lab for Your Patients
With Cancer

Patrice Wendling

February 26, 2020

WASHINGTON —  There's no shortage of interventional cardiology protocols, but when you're called to the bedside of a 58-year-old patient with 4 hours of chest pain, stage 3 lymphoma, and thrombocytopenia, the calculus of when to call the cath lab is complex and the evidence sparse.

"Twenty years ago, I'd walk around and just ask oncologists: 'What's the platelet count that's dangerous?' Somehow or another, 30,000 [mm3] seems to be what I continuously hear, even to this day…even though there's no scientific evidence for how we got to that conclusion," said Jean-Bernard Durand, MD, medical director of Cardiomyopathy Services, University of Texas MD Anderson Cancer Center, Houston.

What is known is that thrombocytopenia is common in cancer patients, and that patients with thrombocytopenia develop acute myocardial infarction (MI), pulmonary embolism (PE), and stroke.

At MD Anderson, 25% of all patients with stroke and one third of those with PE have platelets below 25,000 mm3, he noted. In addition, arterial lines and central lines develop spontaneous thrombi, despite platelets below 25,000.

"The central dogma of low platelets are low-risk for thrombosis — we really need to challenge that," he said here at the American College of Cardiology (ACC): Advancing the Cardiovascular Care of the Oncology Patient conference.

Earlier this month, Durand and colleagues published an algorithm, based on platelet counts and thromboelastography (TEG), that suggests a cutoff of 50,000/mm3 can be used for coronary angiography in patients with cancer who are suspected to have coronary artery disease (CAD).

Under the algorithm, patients with active chest pain and positive troponin or electrocardiographic changes are sent directly to the cath lab for coronary angiography.

In the absence of these changes, the algorithm recommends TEG and a cardio-oncology consultation for patients with mild (platelet count 50,000-90,999/mm3) or moderate (20,000-49,999/mm3) thrombocytopenia; and angiography for patients with higher platelet counts, or those with a diagnosis of acute leukemia or multiple myeloma, regardless of platelet count.

In their experience in 70 patients with cancer (63% hematologic malignancies) who underwent cardiac catheterizations, 100% of those with severe thrombocytopenia (<20,000/mm3) were hypercoaguable on TEG. And, a platelet count below 50,000/mm3 was an independent predictor of worse overall survival at 24 months (hazard ratio, 2.39; 95% confidence interval, 1.12 - 5.06), Durand reported.

If angiography is performed, the algorithm suggests using TEG parameters to guide transfusion in the setting of excessive bleeding. Fresh frozen plasma is recommended for a prolonged reaction time, cryoprecipitate for a low alpha angle, and platelets for a low maximum amplitude.

Durand noted that MD Anderson tends to avoid using prasugrel (Effient, Lilly/Daiichi-Sankyo) for platelet inhibition in patients with cancer who have CAD because of increased cancer risks, a signal picked up in such cardiovascular trials as TRITON and DAPT.

Anticoagulation at the institution is typically 30-50 U/kg of heparin for patients with platelets less than 50,000 mm3 and 50-70 U/kg heparin for those with platelets above 50,000 mm3. More recently, all radial cases also receive more than 3000 U heparin, he said.

"The controversial statement I'm going to make is the idea that perhaps the dosing of milligrams per kilograms, as we always do with anticoagulation, maybe we need to rethink this. Maybe what it's about is how these platelets are functioning," Durand suggested.

While platelet count is a key question before taking a patient with cancer to the cath lab, Durand highlighted other important considerations such as whether metastasis is present, prognosis, goals of the cardiac intervention, access, and whether the patient can tolerate dual antiplatelet therapy for at least 3 months.

Central to it all is the need to consult with oncologists and to build a cardio-oncology team, he said.

"As you get involved with this, you will be called in to drug trials where they're only calculating the maximum-tolerated dose. You're going to have to make a decision in these patients' lives with tyrosine kinase inhibitors, immunotherapy, symptomatic bradycardia, asynchronous rhythms, and, of course, PVI [pulmonary venous isolation], Watchman [left atrial appendage closure device], TAVR [transcatheter aortic valve replacement], and MitraClip — that's the spectrum of individuals," Durand said.

"As you well understand, no one interventionalist can do all this," he stressed. "That's why a team has to be built around a number of interventionalists that can tackle this when we don't have a lot of evidence."

Of note, when surveyed earlier in the day on their knowledge of cardio-oncology, 47% of attendees responded they were "novice (cancer regimens are an alphabet soup)," 48% said they were "competent (I'm okay but need to learn more)," and just 6% rated themselves as "highly proficient (I could be giving these lectures)."

Speaking during the keynote session, ACC president Richard J. Kovacs, MD, Indiana University School of Medicine, Indianapolis, celebrated the "tremendous progress" that has been made in cardio-oncology, citing the worldwide expansion of clinical programs, exponential increase in publications on the subject, and recognition of the need for collaboration between specialties.

But he also left the capacity crowd with a challenge, in light of the huge amounts of digital data now available now in the fourth industrial revolution.

"You have much to do," Kovacs said. "You have an incredibly rapid pace of change; you have a lot to learn, so take advantage of the group here today. But I also challenge you to be the first digitally transformed subspecialty of cardiology and, I would submit, that I think the future depends on it."

American College of Cardiology: Advancing the Cardiovascular Care of the Oncology Patient: Presented February 15, 2020.

Front Cardiovasc Med. Published online February 14, 2020. Full text

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