No evidence for ischemic preconditioning during repeated vessel occlusion in coronary angioplasty

A minimal resting time of 25 min is needed before measuring stabilized blood pressure in subjects addressed for vascular investigations

Blood pressure (BP) measurement is a central element in clinical practice. According to international recommendations 3 to 5 minutes of resting is needed before blood pressure measurement. Surprisingly, no study has modelled the time course of BP decrease and the minimum resting-time before BP measurement. A cross-sectional bicentric observational study was performed including outpatients addressed for vascular examination. Using two automatic BP monitors we recorded the blood pressure every minute during 11 consecutive minutes. The data was analyzed by non-linear mixed effect regression. Systolic (SBP) and diastolic BPs were studied and we tested the effect of covariates on its evolution through log-likelihood ratio tests. We included 199 patients (66+/−13years old). SBP was found to decrease exponentially. Simulations based on the final model show that only half the population reaches a stabilized SBP (defined as SBP + 5 mmHg) after 5 min of resting-time while it takes 25 min to ensure 90% of the population has a stabilized SBP. In conclusion, our results and simulations suggest that 5 minutes are not enough to achieve a stabilized SBP in most patients and at least 25 minutes are required. This questions whether the diagnosis of hypertension can be reliably made during routine visits in general practitioners’ offices.

Pharmacological modulation of the ATP sensitive potassium channels during repeated coronary occlusions: no effect on myocardial ischaemia or function

BACKGROUND

Repeated episodes of myocardial ischaemia may lead to ischaemic preconditioning. This is believed to be mediated by the ATP sensitive potassium channels.

OBJECTIVE

To examine the effect of pharmacological modulation of the ATP sensitive potassium channels during repeated coronary occlusions.

DESIGN

Double blind, double dummy study.

METHODS

38 patients with a proximal stenosis of the left anterior descending coronary artery and no visible coronary collateral vessels underwent three identical 90 second balloon occlusions, each followed by five minutes of reperfusion. The patients were randomised to pinacidil 25 mg, glibenclamide 10.5 mg, or matching placebo 90 minutes before the start of the procedure. Myocardial ischaemia was measured by continuous monitoring of ECG ST segment changes. Changes in left ventricular function were recorded with a miniature radionuclide detector, and angina was scored on the Borg scale.

RESULTS

In all patients the first balloon occlusion led to significant ST segment elevation, a clear decrease in left ventricular ejection fraction, and angina pectoris. This response was not attenuated at the second or third balloon occlusion, either in the placebo group or in the patients pretreated with pinacidil or glibenclamide.

CONCLUSIONS

Under the given experimental conditions, this randomised and double blind study did not support the view that the human myocardium has an intrinsic protective mechanism that is activated by short lasting episodes of ischaemia.

Ischemic preconditioning does not improve myocardial preservation during off-pump multivessel coronary operation

BACKGROUND

The value of ischemic preconditioning during coronary operations has remained controversial. The aim of this study was to evaluate the effects of ischemic preconditioning on myocardial energy metabolism and tissue injury during off-pump multivessel coronary surgery.

METHODS

Eleven patients with preceding preconditioning were compared with 11 patients without it. The preconditioning group underwent a 5-minute period of ischemia followed by a 5-minute reperfusion period before coronary occlusion for each of the first two anastomoses.

RESULTS

The transmyocardial differences (coronary sinus - arterial) in inosine and the sum of adenine degradation products increased in both groups, but the differences in xanthine and hypoxanthine increased only in the preconditioning group. Myocardial lactate production increased to a maximum of 0.09 mmol/L with preconditioning and to a maximum of 0.17 mmol/L without it. Transmyocardial pH differences increased to 0.03 U in both groups. The maximum postoperative concentration of creatine kinase-MB mass was 14.8 microg/L with preconditioning and 6.3 microg/L without preconditioning, and that of troponin I 7.4 microg/L and 5.2 microg/L, respectively. There were no statistically significant differences between the groups, however.

CONCLUSIONS

Ischemic preconditioning of 5 minutes followed by reperfusion of 5 minutes during off-pump multivessel coronary artery surgery did not prevent myocardial metabolic derangement and tissue injury and thus cannot be routinely recommended.