Objective To investigate the underlying mechanisms of a decreased coronary flow reserve after myocardial infarction (MI) by analysing the characteristics of the diastolic hyperaemic coronary pressure-flow relationship.
Design Prospective study
Setting Tertiary care hospital
Patients 68 patients with a recent MI (3-12 days) and 27 patients with stable angina pectoris (AP, control group)
Main outcome measures The intercept with the pressure axis (the zero flow pressure or Pzf) and slope index of the pressure-flow relation (SIFP) were calculated from the simultaneously recorded hyperaemic intracoronary blood flow velocity and aortic pressure after successful coronary stenting.
Results There was a stepwise increase of Pzf from AP (14.6±8.0mmHg), over non-Q-wave MI (22.5±9.1mmHg), to Q- wave MI (37.1±12.9mmHg) (p<0.001). Similar changes in Pzf were observed in a reference artery perfusing non-infarcted myocardium. Multivariate analysis showed that in both regions the left ventricular end diastolic pressure was the most important determinant of the Pzf. <BR> The SIFP was not statistically different in the treated vessel between MI and AP patients but was increased in MI patients with a markedly elevated left ventricular end diastolic pressure.
Conclusions After a MI, the coronary pressure-flow relationship is shifted to the right both in the infarcted and non-infarcted remote myocardium, as evidenced by the elevated Pzf. The correlation with Pzf suggest that elevated left ventricular filling pressures contribute to the impediment of myocardial perfusion in infarction patients.
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