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Is the development of myocardial tolerance to repeated ischemia in humans due to preconditioning or to collateral recruitment?

^a Division of Cardiology, University Hospital, Bern, Switzerland

View larger version (30K): [in a new window]   Figure 1 Tracings of simultaneous mean aortic pressure (Pao), distal coronary artery pressure (Poccl) and an intracoronary (i.c.) electrocardiographic (ECG) lead obtained in a patient with marked collateral recruitment during the three 2-min coronary artery occlusions (time: horizontal axis). The distal coronary artery pressure during the balloon occlusions (i.e., i.c. wedge pressure, Poccl = 12 mm Hg) is close to the dotted line (= 10 mm Hg) and increases during as well as between each of the occlusions. Meanwhile, Pao remains relatively constant. Collateral flow index during each of the occlusions is calculated as (Poccl – CVP)/(Pao – CVP); CVP: central venous pressure = 5 mm Hg. The i.c. ECG lead obtained via the pressure guidewire for the measurement of Poccl shows marked ST elevation during the occlusions that decreases between the first and third occlusion.

View larger version (30K): [in a new window]   Figure 2 Tracings of simultaneous Pao, distal coronary artery pressure and an i.c. ECG lead obtained in a patient with little collateral recruitment during the three 2-min coronary artery occlusions (time: horizontal axis). The dotted line indicates a pressure of 5 mm Hg. The i.c. ECG ST segment elevations during the three occlusions remain constant. See Figure 1 for the calculation of the collateral flow index. Abbreviations as in Figure 1.

View larger version (42K): [in a new window]   Figure 3 Individual data of collateral flow index (CFI; vertical axis, left-hand side) and the ST segment shift (normalized intracoronary electrocardiographic [ECG] ST shift; vertical axis, right-hand side) during the three subsequent 2-min coronary artery occlusions (horizontal axis) for the patients receiving i.c. adenosine (2.4 mg/min, panel A) and for those receiving normal saline (NaCl, panel B). The filled symbols with vertical lines indicate mean values ± SD.

View larger version (25K): [in a new window]   Figure 4 Combined mean values (± SD, vertical lines) of the normalized intracoronary electrocardiographic (ECG) ST elevation (squares, vertical axis, left-hand side) and the collateral flow index (CFI) (triangles, vertical axis, right-hand side) during the three subsequent 2-min balloon occlusions (horizontal axis) for the patients pretreated with adenosine (A) and for those pretreated with normal saline (B).

View larger version (23K): [in a new window]   Figure 5 Inverse correlation between the change in collateral flow index (CFI, no unit; horizontal axis) and the normalized intracoronary electrocardiographic (ECG) ST-elevation changes (ST, no unit; vertical axis) determined from the first to the third occlusion. Filled symbols: patients pretreated with adenosine; open symbols: patients pretreated with normal saline.