Arterial thrombosis occurs in about 1 in 10 children who undergo cardiac catheterization, predominantly in infants, according to a single-center study published online January 23, 2015, ahead of print in Heart.

Careful postprocedural monitoring of these young patients is important to detect thrombosis early and initiate anticoagulant therapy, the authors say.

Investigators led by Manuela Albisetti, MD, of University Children’s Hospital Zurich (Zurich, Switzerland), looked at 123 children—30% of them infants 12 months or younger and the rest aged 1 to 19 years—who underwent cardiac catheterization by the femoral route for diagnosis or intervention at their institution over a 12-month period. Cannulation of a femoral vein was also performed as needed in 87 patients, 37% of them infants.

In addition to weighing less and being shorter, infants wore compression bandages for a shorter time and were more likely than older children to have cyanotic disease.

Events Occurred Despite Anticoagulation

The mean procedure time was 94.31 minutes, and the number of puncture attempts ranged from 1 to 6 (median of 1). After puncture, unfractionated heparin at a bolus dose of 100 IU/kg was administered intravenously and repeated at a dose of 50 IU/kg after 1 hour. Anticoagulation was monitored every 30 minutes using an activated clotting time target of 250 seconds.

Immediately after catheterization, patients received enoxaparin subcutaneously at a dose of 1.5 mg/kg every 12 hours in infants under 2 months old and 1.0 mg/kg in older children. The drug was continued for 24 hours after diagnostic procedures and 48 hours after interventional procedures. Beginning the evening after the latter, children also received 3 to 5 mg/kg of aspirin a day for 3 or 6 months, depending on the procedure.

Overall, arterial thrombosis occurred in 14 children (11.4%). Twelve of the clots developed in infants (86%) and 2 in older children (14%). Among infants 4 weeks old and younger, 57% developed arterial thrombosis.

Three factors were associated with a lower likelihood of thrombosis:

• Older age (OR 0.49; 95% CI 0.28-0.86)
• Higher body weight (OR 0.78; 95% CI 0.65-0.92)
• Greater height (OR 0.93; 95% CI 0.90-0.97)

In addition, there was a trend toward more thrombosis in patients having a diagnosis of cyanotic cardiac disease (OR 2.87; 95% CI 0.90-9.15). In a logistic regression analysis restricted to infants no older than 12 months, older age was still associated with reduced likelihood of thrombosis (OR 0.001; 95% CI 0.00-0.18).

Postprocedural Monitoring Important

Pedal pulses were palpated every hour during the first 6 hours after catheterization and then every 8 hours. If pulses on the punctured leg were absent or weaker compared with the contralateral pulses, they were verified with Doppler ultrasound and blood pressure measured via Doppler. Whenever decreased perfusion was suspected, Doppler imaging was performed to rule out arterial thrombosis.

If thrombosis was diagnosed, children were treated with low molecular weight heparin or unfractionated heparin until clinical and radiological resolution of the clot and for a maximum of 4 weeks. If thrombosis persisted after that point, heparin was changed to aspirin for 3 to 6 months. Children were seen 3 months after first diagnosis and then yearly. Follow-up visits included clinical and ultrasound examinations.

The authors observe that the younger and smaller the child, the smaller the vessels. “Often a vasospasm occurs after puncturing the small vessels, increasing the risk for injuring the intima by the catheter movements, which predispose for developing a thrombus,” they explain. 

Previous studies have reported an incidence of postcatheterization thrombosis ranging from 0 to 30%, the investigators note. They suggest possible explanations for the wide variation, including:

Differences in study design

Exclusion or inclusion of older children

Varying clinical and radiological criteria for diagnosis of thrombosis

Differing time points for diagnosis after catheterization (arterial pulses may recover over time due to angiogenesis)

 

Based on the findings, “a well-defined clinical diagnostic tool may be more sensitive than a routinely performed Doppler ultrasound the day after the [cardiac catheterization], when remodeled vessels are possibly and, in our experience, often mistaken for the femoral artery in the case of small infants,” Dr. Albisetti and colleagues say. Mobilization of the patients, removal of the compression bandage, resorption of the hematoma, thrombus resolution, and/or remodeling of small dissection flaps may also contribute to the recovery of arterial pulses, they add.

 

Procedural Factors May Also Play a Role

“The incidence [of thrombosis] reported in this study is much higher than what I have experienced and even higher than most of the cited literature,” Ziyad M. Hijazi, MD, MPH, of Sidra Medical and Research Center (Doha, Qatar), told TCTMD in an email.

In general, complication rates are lower today due to the availability of 3-Fr sheaths, he observed, adding that every pediatric cath lab should have all sizes of sheaths and catheters on hand.

Dr. Hijazi cited a number of factors beyond sheath size and the reported predictors that can also affect the chance of thrombosis:

• Operator experience
• Number of puncture attempts
• Site of puncture, which correlates with the size of the vessel canalized

Thrombosis is usually not difficult to diagnose, he observed—especially the more severe forms that can lead to limb ischemia—but Doppler ultrasound should always be used in conjunction with clinical examination, he commented.

With regard to thrombosis treatment, Dr. Hijazi expressed surprise that the investigators failed to mention tissue plasminogen activator (tPA). “In the protocol we use, if heparin does not work within 6 hours, we switch to tPA,” he said.

 

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Source:
Brotschi B, Hug MI, Kretschmar O, et al. Incidence and predictors of cardiac catheterization-related arterial thrombosis in children. Heart. 2015;Epub ahead of print.

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