Systolic time intervals after phenylephrine administration for early stratification of patients after acute myocardial infarction

Cardiovascular dysfunction in dogs associated with critical illnesses

The records of 16 dogs with left ventricular dysfunction associated with severe systemic illness were reviewed. The most common diagnoses in affected dogs were sepsis and cancer. Despite left ventricular dysfunction, no dog presented with signs of congestive heart failure. Fifteen dogs were presented with generalized weakness as a part of their clinical complaint. Twelve (75%) of 16 dogs died or were euthanized within 15 days of admission to the hospital. The average time until death was 3.6 days.

Estimation of myocardial performance in CABG patients

Myocardial performance index (MPI) permits a relative easy estimation of global left ventricular (LV) systolic and diastolic function. It was shown that MPI inversely correlated strongly with the maximum derivative of LV pressure with respect to time (+dP/dtmax). The current study evaluated the change of MPI during and immediately after coronary artery bypass surgery (CABG) surgery and analyzed the relationship between MPI and hydraulic energy (exemplified by preload adjusted maximal power-PAMP) during that same period. The study was conducted in 45 patients undergoing CABG. After induction of anaesthesia, 10 min after revascularization and 2 h postoperatively, haemodynamics were assessed. Preload was characterized by LV end-diastolic area indexed for BSA (LVEDAI); afterload was estimated by arterial elastance (Ea) and indexed systemic vascular resistance (SVRI). Global myocardial performance was indicated in terms of MPI and contractility was achieved by PAMP. Myocardial performance index increased postoperatively (0.44 +/- 0.13, 0.37 +/- 0.17 and 0.50 +/- 0.16, respectively; P < 0.001). Preload adjusted maximal power did not alter significantly (1.90 +/- 1.24, 2.02 +/- 1.34 and 2.12 +/- 1.00 W cm(-2)*10(4), respectively). Left ventricular enddiastolic area indexed did not change. Arterial elastance augmented to 0.76 +/- 0.39, 0.80 +/- 0.40 and 1.01 +/- 0.43 mmHg ml(-1), respectively; P < 0.001. Systemic vascular resistance did not change. A relationship was found between 1-MPI/LVEDAI2 and PAMP (R2 = 0.50). This study shows that in the setting of CABG surgery, MPI appears to be a good measure of global LV function.

Blood pressure elevation after phenylephrine infusion may adversely affect myocardial perfusion in patients with coronary artery disease

BACKGROUND

Although blood pressure is a major determinant of myocardial oxygen-demand, little information is currently available regarding the changes in blood pressure (BP) during myocardial ischemia. Since BP elevation may cause left ventricular (LV) wall stress and an increase in oxygen demand, infusion of an alpha-adrenergic agonist, such as phenylephrine (PH), may provoke changes in myocardial perfusion in coronary artery disease (CAD) patients. As the effects of BP changes alone on myocardial perfusion have never been assessed by thallium-201 (Tl) scintigraphy, we investigated the effects of BP elevation after PH infusion, in order to study the hypothesis that pressure loading alone without increases in heart rate, may provoke transient impairment of regional myocardial perfusion, in CAD patients.

PATIENTS AND METHODS

Forty-one (41) patients with angiographically documented CAD, aged 54+/-8 years, were included in our study. Each patient was given, without any complications, a PH (0.1 mg/ml) dose infused at a rate of 0.8 ml/mm, determined by a standardisation procedure and producing a mean blood pressure elevation of approximately 30% above baseline levels and a heart rate response to levels of no less than 50 bpm. One minute after the desired blood pressure and heart rate responses were reached, 2 mCi of Tl were injected and the PH infusion continued until the termination of the test. Tl scintigraphy was performed both 2 min after Tl injection and 4 h later, while the results were correlated to coronary angiography findings.

RESULTS

PH scintigraphy produced 152 total defects. The mean perfusion defect size (%) was 14+/-12 and was directly related to the number of diseased vessels, i.e., 2% for one-vessel disease, 15% for two-vessel disease and 25% for three-vessel disease (P<0.05). The lowest percentage Tl activity values were 56+/-14 and were inversely related to the number of diseased vessels (P<0.01). The mean Tl lung counts/pixel values were 25+/-8 while it increased as the number of diseased vessels increased (P<0.01). The mean lung/heart ratio values were 0.31+/-0.08 while it increased as the number of diseased vessels increased (P<0.01).

CONCLUSION

BP elevation after PH loading, produces a significant impairment of myocardial perfusion, that correlates well with the extend of angiographic findings.