Non-invasive low frequency vibration as a potential emergency adjunctive treatment for heart attack and stroke. An in vitro flow model.

BACKGROUND

Myocardial infarction and stroke (arterial thrombosis) comprise the leading killers and sources of disability in the developed world, and incomplete thrombolysis along with high bleeding rates (plus late presentations to cathlabs) have prompted an intensive search for alternative or adjunctive emergency therapies. Transcutaneous ultrasound has been studied in remediation of thrombosis, but has been problematic due to poor penetration, risk of arterial damage, plus the apparent need for a highly skilled approach. Surprisingly there has been no reported studies on the much simpler application of transcutaneous low frequency vibration (well known for its superior penetration and flow enhancing characteristics) to assist arterial thrombolysis. The aim of our experiment therefore was to test the hypothesis whether vibration (i.e. approximately 100 Hz, 0.5 mm), when applied across an attenuating barrier, would assist recanulization of a thrombosed flow system held at arterial like pressure.

METHODS

A teddy bear with a 2 cm slab of New York Steak placed upon its chest surface was used as a test subject with an in-dwelling catheter (approximately 4.0 mm lumen) cannulated through the bear's thorax. In a series of test runs (n=30), a 2 h old (or older) blood clot was injected into the catheter such as to occlude it at a stenosis site (approximately 90% luminal narrowing) created by a clamp placed along the catheter within the teddy's chest region. A pressurized heparinized IV system was in all cases connected to the catheter such as to yield an "arterial like" lumen pressure proximal the obstruction. For each test run, after a twenty minute observation period to confirm stability of the occlusion, test groups where randomized to receive vibration to the slab of steak upon the teddy's "chest wall" (generally overlying the site of the thrombotic obstruction), or no vibration for an evaluation period of up to 45 min.

RESULTS

Catheter reflow occurred rapidly (median reflow-time 90 s) in the vibration groups within the evaluation period (i.e. 15/17), while the system remained otherwise blocked in the control groups receiving no vibration (i.e. 0/13). The difference in flow system patency rate for the vibration groups vs. the control groups was statistically significant (P=0.0000009).

CONCLUSIONS

The frequent and generally rapid re-establishment of flow in vibration groups compared to the complete absence of reflow in control groups confirms the hypothesis that vibration applied across a physical barrier assists clearance of a blood clot in a stenosed flow system under systemic levels of pressure. We studied the incidence of clearance of a blood clot within a stenosed, heparanized catheter system held at arterial like pressure that was treated with externally delivered low frequency vibration (applied proximate the thrombotic occlusion across an attenuating medium--a 2 cm thick slab of New York Steak--at approximately 100 Hz, 0.5 mm), versus no vibration. Reflow in test runs incorporating vibration occurred faster, and resulted in significantly greater recanulization rates in the catheter system versus test runs without vibration (P=0.0000009). Non-invasive vibration holds potential as an adjunct to pharmacologic therapy in treatment of acute arterial thrombosis. Further study of this technique appears warranted in live animal models.