Analysis of cardiac lymphatic dynamics in beating canine hearts using a high-speed CCD microscope

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Control of the interstitial fluid in the myocardium is very important, since interstitial edema has been demonstrated to impair cardiac function. To evaluate the cardiac lymphatic dynamics, we measured phasic diameter changes and flow velocity waveform of the epicardial lymphatics during a cardiac cycle. In 10 anesthetized open-chest dogs, India ink and suspension fluid (Levovist) were injected through a 27-gauge needle into the myocardium of the left ventricular apex for visualization of the lymphatic network and flow velocity, respectively. The cardiac lymphatics were visualized by India ink using a needle-lens CCD microscope at end-diastole and end-systole under control conditions. Velocities of Levovist flowing in the epicardial lymphatics were calculated by frame-to-frame analysis using a high-speed CCD microscope based on the moving distance of Levovist suspension per 5 ms. The lymph vessels with valves were clearly visualized in all cases. The diameters of epicardial lymphatics showed an increasing trend from 179 ± 47 μm at end-diastole to 185 ± 44 μm at end-systole without statistical significance. The cardiac lymph flow velocity was accelerated in early systolic phase. The mid-systolic dip was followed by late systolic and then early diastolic forward flow. A reverse flow was observed in some cases during late diastolic phase. In conclusion, because of small phasic diameter changes during a cardiac cycle, drainage of cardiac lymph is not controlled on a beat-to-beat basis. Cardiac lymphatic flow was slow but exhibited a unique phasic pattern during a cardiac cycle. Flow-velocity pattern indicated that major determinants of cardiac lymph dynamics during systole may be myocardial strain and intramyocardial pressure due to myocardial contraction.