Immediate effect of Biosense guided percutaneous direct myocardial revascularization with holmium:yttrium aluminium garnet laser on myocardial contractility assessed by transesophageal echocardiography

OBJECTIVE: To evaluate immediate changes in left ventricular wall motion in patients treated using Biosense direct myocardial revascularization laser system. METHODS: Regional wall motion in 10 patients undergoing catheter-based direct myocardial revascularization using a holmium:yttrium aluminium garnet laser was assessed by transesophageal echocardiography before and immediately after the procedure. RESULTS: Mild deterioration in wall-motion score occurred rarely for only three of 160 (1.9%) segments and did not induce clinical heart failure. CONCLUSION: With the current catheter-based laser myocardial revascularization strategy, mild deterioration in wall motion of treated segments was rarely observed and did not effect overall left ventricular function or induce clinical congestive heart failure.     

Electromechanical characterization of acute experimental myocardial infarction

OBJECTIVE: A new cardiac mapping system combines harmless magnetic field energy and tip-deflecting catheters (equipped with location sensors) to obtain real-time 3-dimensional electromechanical maps of the left ventricle endocardial surface without using x-ray fluoroscopy. This experimental study assessed electromechanical changes during acute coronary occlusion and reperfusion in a canine model. METHODS: Group 1 (n = 10) underwent coronary occlusion for 45 minutes followed by reperfusion (n = 6) and group 2 (n = 11) underwent coronary occlusion for 90 minutes. Endocardial peak-to-peak voltage amplitudes and local endocardial shortening values were measured in ischemic and non-ischemic zones at baseline, following coronary occlusion and reperfusion. RESULTS: In ischemic zones, local shortening was significantly reduced during coronary occlusion compared to baseline (Group 1: 4.7 +/- 2.0% at 45 minutes vs. 15.5 +/- 3.4%, p < 0.001, 6.2 +/- 2.1% at 90 minutes vs. 15.5 +/- 3.4%, p < 0.001; Group 2: 5.0 +/- 2.9% at 90 minutes vs. 13.9 +/- 3.3%, p = 0.007). Coronary occlusion caused a significant reduction in voltage potentials in the ischemic area (unipolar voltage at 45 minutes: 32.2 +/- 7.3 mV vs. 36.2 +/- 8.5 mV at baseline, p = 0.03; unipolar voltage at 90 minutes: 30.5 +/- 11.3 mV vs. 38.3 +/- 14.2 mV, p = 0.003; bipolar voltage at 45 minutes: 7.6 +/- 5.5 mV vs. 10.1 +/- 6.0 mV, p < 0.04; bipolar voltage at 90 minutes: 7.6 +/- 4.4 mV vs. 9.8 +/- 6.2 mV, p < 0.02). Voltage amplitudes were no longer reduced during reperfusion (unipolar voltage: 34.3 +/- 10.5 mV vs. 36.2 +/- 8.5 mV, p = 0.26; bipolar voltage: 9.1 +/- 4.5 mV vs. 10.1 +/- 6.0 mV at baseline, p = 0.37), or in non-ischemic regions during either coronary occlusion or reperfusion. CONCLUSIONS: Electromechanical mapping study provides unique insights into acute myocardial infarction and stunning by detection and localization of early electromechanical changes during coronary occlusion and/or reperfusion.     

The relative importance of thrombin inhibition and factor Xa inhibition to the antithrombotic effects of heparin

The relative importance of antithrombin and anti-factor Xa activities of heparin fractions required to achieve optimal antithrombotic effects is unknown. To study this, we measured the effects of standard heparin, an octasaccharide heparin fraction (anti-factor Xa activity only), and dermatan sulfate (antithrombin activity only) on the prevention of thrombosis and related this to their anticoagulant effects in vivo in rabbits. Thrombosis was measured as the incorporation of 125I- fibrinogen into tissue thromboplastin-induced thrombi using a Wessler- type model. Ex vivo changes in thrombin clotting time (TCT) were used as an index of antithrombin activity, and a chromogenic anti-factor Xa assay was used to measure anti-factor Xa activity. In addition, the ability of the three sulfated polysaccharides to simultaneously inhibit the generation of thrombin activity and to enhance the inactivation of the factor Xa added to initiate thrombin generation in plasma was determined. Standard heparin, in a dose of 10 anti-factor Xa U/kg, inhibited thrombus formation by 90%, prolonged the TCT by two seconds, and resulted in an anti-factor Xa level of 0.32 U/mL. The octasaccharide heparin fraction, in a dose of 10 anti-factor Xa U/kg, inhibited thrombus formation by 41%, had no effect on the TCT, and resulted in an anti-factor Xa level of 0.28 U/mL. Higher doses of the octasaccharide resulted in a further increase in the anti-factor Xa levels but had no further effect on thrombus formation. Dermatan sulfate, in a dose of 500 micrograms/kg, inhibited thrombus formation by 95%, but had no affect on the TCT. These results indicate that the antithrombotic effect achieved by inhibiting factor Xa is limited and that better antithrombotic effects are achieved by heparin or heparin- like substances capable of influencing the inactivation and/or the generation of thrombin.