Coronary artery disease
Time Course of Microvascular Resistance of the Infarct and Noninfarct Coronary Artery Following an Anterior Wall Acute Myocardial Infarction

https://doi.org/10.1016/j.amjcard.2005.11.026Get rights and content

Previous studies have suggested that coronary flow velocity reserve (CFVR) in the early phase of acute myocardial infarction (AMI) is abnormal in infarcted and remote regions. This study determined the coronary microvascular resistance of infarct-related arteries (IRAs) and non-IRAs during AMI and at follow-up in patients who were treated with primary percutaneous intervention. In 73 patients with a first anterior wall AMI, baseline and minimal microvascular resistance in IRAs and non-IRAs immediately after reperfusion and at 1-week and 6-month follow-up were calculated as the ratio of mean transvascular pressure gradient to mean baseline and to adenosine-induced hyperemic blood flow velocity, respectively. CFVR in IRAs increased from 1.6 ± 0.4 after reperfusion to 1.9 ± 0.5 at 1 week and to 3.0 ± 0.8 at 6 months (p <0.0001) and in non-IRAs from 2.4 ± 0.5 to 2.7 ± 0.6 at 1 week to 3.3 ± 0.6 at 6 months (p <0.0001). Minimal microvascular resistance in IRAs and non-IRAs (3.2 ± 1.7 and 2.2 ± 0.6 mm Hg/second/cm, respectively) decreased significantly at follow-up (2.0 ± 0.6 and 1.7 ± 0.6 mm Hg/second/cm at 1 week and 1.8 ± 0.6 and 1.8 ± 0.7 mm Hg/second/cm at 6 months, respectively). After correction for rate–pressure product, baseline microvascular resistance after reperfusion and at 6 months did not significantly differ between IRAs and non-IRAs. In conclusion, minimal microvascular resistance is higher in infarcted and noninfarcted regions during AMI than at follow-up. The low CFVR in remote regions during AMI is probably due more to disturbed autoregulation than to increased myocardial workload.

Section snippets

Patient selection

We studied 100 consecutive patients who presented with a first anterior wall AMI that was treated with primary angioplasty. AMI was defined as chest pain that lasted >30 minutes in conjunction with persistent ST-segment elevation ≥2 mV in 2 adjacent precordial leads. Exclusion criteria were cardiogenic shock (systolic blood pressure <90 mm Hg despite conservative measurements), previous AMI, previous coronary artery bypass surgery, previous left ventricular ejection fraction <40%, acute

Results

Patients’ baseline characteristics are listed in Table 2.

A time-dependent improvement of CFVR in IRAs and non-IRAs remained significant after correction for the rate–pressure product (Table 1). Uncorrected and corrected baseline average peak blood flow velocities in IRAs were higher than those in non-IRAs after angioplasty (p <0.01) and at 1-week follow-up (p <0.01). However, at 6-month follow-up, uncorrected and corrected baseline average peak blood flow velocities in IRAs equaled values in

Discussion

This study demonstrates, in a homogenous cohort of patients with a first anterior wall AMI, increased levels of minimal microvascular resistance and decreased values of CFVR in IRAs and non-IRAs. Further, this study shows that microvascular function improved during 6-month follow-up in the 2 territories. Our study confirms previous observations that CFVR in IRA is decreased after reperfusion in the early phase of AMI secondary to a low hyperemic flow velocity.2, 3 Impairment of hyperemic flow

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