Cath Lab Digest

Listen to the full podcast of this interview at http://vasculardiseasemanagement.com/content/dr-tod-c-engelhardt-discuss...

Tell me about your recently published study regarding the use of catheter-directed ultrasound-accelerated thrombolysis for the treatment of pulmonary embolism.

This is a really exciting new thing for me, and actually a new thing for the world for that matter, in the treatment of pulmonary embolism. Pulmonary embolism can be and frequently is a life-threatening condition and we’re taking patients now with a significant clot burden, a significant degree of debility from pulmonary embolism, and treating them with ultrasound-assisted thrombolysis, which means that we are using a drug to dissolve blood clots in combination with ultrasound technology. The 2 combined have resulted in rapid dissolution of the clot from the pulmonary circulation, which immediately lessens the risk of death in these patients.

I treated 24 patients who had massive or submassive pulmonary emboli. This is really the main cause of death in pulmonary embolism patients: right heart failure. If you can reverse that debilitation of the right heart using this new technology, within 12 to 24 hours, the right heart goes back to normal dimensions, immediately lessening the risk of death from heart failure. We’re also showing that the patients symptomatically get better and it involves placement of catheters, very small catheters with tiny ultrasound transducers spaced 1 cm apart placed directly into the pulmonary artery through a transvenous approach. In other words, we go through the groin, the femoral veins, bilaterally or unilaterally. We don’t have to stick both sides even to place catheters in both pulmonary arteries. We run a drip of TPA, tissue plasminogen activator, a clot-dissolving drug. That is a continuous slow drip through the catheter that’s placed in the pulmonary artery within the clot in the artery and we activate the ultrasonic transducers simultaneously with drug administration. The whole reason why this works so well is the ultrasound technology. The ultrasound causes acoustic pressure waves, which break up the clot and expose fibrin receptor cites and the TPA can get into the inner surface of the clot where it can do its work in dissolving the blood clot.

We have great results. One of the best things is that we proved safety with this. The 2 things I like to do when we do a study like this is safety and efficacy. We need to know number 1 that the device we are going to use is safe. We also need to know that it’s effective. It does us no good if the safety profile is poor or if it’s just not effective to use. Delightfully, we were able to prove both in the first 24 patients that we treated and we were able to show with pretreatment compared to post-treatment CAT scans that the clot burden was relieved to a significant degree. With the enlarged right heart when compared to the left heart (we compared a right ventricular to left ventricular ratio), we proved that ratio can be brought down to normal or near-normal. So far, we have no deaths and we are showing safety and efficacy with this technology.

What was the success rate of the patients you treated in this study?

We’ll need to talk about 2 definitions of success rate. We were able to successfully place the catheter and do the treatment in 100% of patients without difficulty, which was truly a success. In the article, it lists exactly how many patients we treated and gives you a graph on how many patients had regression of right ventricular enlargement and I would say that all of our patients had improvement in their condition based upon symptoms and objective criteria, or the CAT scan measurements. Some had more dramatic positive results than others but 100% went the right way, experiencing symptomatic relief and we were able to objectively measure beneficial effects of the therapy.

What other devices have you used and what do you find helpful about those?