Continuous monitoring of global left ventricular ejection fraction during percutaneous transluminal coronary angioplasty

Validity of ejection fraction as a measure of myocardial functional state: impact of asynchrony

AIMS

The goal of this study was to test whether peculiarities of left ventricular (LV) regional function place limits on the validity of ejection fraction (EF) as a measure of the myocardial functional state.

METHODS AND RESULTS

Transthoracic and transoesophageal data from patients with a variety of cardiac conditions were used for analysis of LV regional function. The focus was on the effects of mechanical asynchrony. Ejection fraction was calculated on the basis of LV end-diastolic volume and end-systolic volume obtained by two different ways: (i) end-systolic volume as a whole; and (ii) the sum of all regional end-systolic volumes (which may occur at different times). The relative difference, D-EF, between EFs obtained by (i) and (ii) was taken as the 'merit' of EF. A value of zero is the highest merit. Irrespective of the examination method, we found that D-EF was always higher than zero, and that its value depended on the extent of mechanical asynchrony.

CONCLUSIONS

Ejection fraction is not the arithmetic average of regional EFs. An increase of asynchrony increases D-EF, i.e. it reduces the merit of EF as a measure of cardiac function.

Effect of clinical variables on the correlation between amount of ST elevation and myocardial scintigraphic perfusion defect during coronary occlusion

PURPOSE

We investigated if the correlation between the amount of ST elevation (STE) and myocardial ischemia could be altered by variables such as hypertension or body mass index (BMI).

METHODS

A 12-lead electrocardiogram and a technetium-99m tetrofosmin injection were performed during balloon coronary occlusion in 34 patients with single-vessel disease.

RESULTS

The sum of STE correlated with scintigraphic extent of ischemia (r = 0.441; P = .009), but this correlation improved significantly in men and patients with BMI of 28 kg/m2 or less and was highest in nonhypertensive patients (r = 0.763; P < .001). In contrast, it was poor in women and patients with BMI greater than 28 kg/m2 or arterial hypertension, being lowest in the latter subset (r = 0.110; P = .664). Moreover, 8 (80%) of 10 patients with extensive hypoperfusion but with low SigmaSTE (< or =20 mm) were hypertensive.

CONCLUSIONS

If confirmed by larger studies, electrocardiographic underestimation of transmural ischemia during coronary occlusion in patients with hypertension or increased BMI may lead to adjustments in STE criteria for reperfusion therapy.

Reduced high-frequency QRS components in patients with ischemic heart disease compared to normal subjects

Analysis of high-frequency QRS components (HF-QRS) might provide an additional method when diagnosing various heart diseases, for example ischemic heart disease (IHD). This study compares HF-QRS in normal subjects to those in patients with IHD, and also analyzes HF-QRS considering gender and age. A total of 63 normal subjects and 64 patients with IHD were included. Signal-averaged electrocardiograms (ECGs) from the 12 standard leads were analyzed in the frequency interval of 150-250 Hz. The results showed that the summed 12 lead HF-QRS in patients with IHD were significantly lower than in normal subjects (mean summed HF-QRS was 33.5 microV in the IHD group, 43.7 microV in normal individuals, P <.0005). HF-QRS were not statistically associated with gender or age (P =.820 and P =.573, respectively). However, the inter-individual variation of HF-QRS was large in both groups which probably limits the clinical usefulness of the method.

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.

Effects of ischemic preconditioning and synchronized coronary venous retroperfusion in an off-pump coronary artery bypass grafting model

Off-pump coronary artery bypass grafting (CABG) has become a popular procedure. However, temporary occlusion of the target vessel is sometimes a threat to the patients. Although ischemic preconditioning (IP) has been proposed to reduce myocardial injury, its effects remain controversial. The coronary veins represent an alternate route for delivery of therapeutic agents and arterial blood to the acutely ischemic myocardium. The aim of this study was to investigate the protective effect against myocardial ischemia and reperfusion injury of combined IP and synchronized coronary venous retroperfusion (SCVR) in an off-pump CABG model. Twenty-one pigs were assigned to 3 groups of 7 animals. In the control group, the left anterior descending coronary artery (LAD) was occluded for 45 min followed by 2 h of reperfusion using a left intrathoracic artery (LITA) bypass circuit. In the IP group, LAD occlusion was done for 5 min with 15 min of reperfusion, followed by 45 min of LAD occlusion. In the SCVR group, pretreatment before LAD occlusion was the same as in the IP group. Then, SCVR was commenced just after the start of LAD occlusion for 45 min. The percent systolic shortening of ischemic myocardium (measured by sonomicrometry) after reperfusion via the LITA was significantly (p < 0.001) greater in the SCVR group (14.6 +/- 3.3%) than in the control group (-1.6 +/- 5.6%, 95%CI: -24.3 - -8.1) or the IP group (0.7 +/- 8.0%, 95%CI: -22.0 - -5.8) after 30 min of reperfusion, and this difference persisted throughout the reperfusion period. Infarct size (expressed as a percentage of the area at risk) was significantly (p < 0.001) smaller in the SCVR group (2.4 +/- 2.7%) than in the control group (83.0 +/- 2.3%, 95%CI: -99.0 - -62.4) or the IP group (42.0 +/- 23.0%, 95%CI: -58.0 - -21.3). Combined SCVR and IP had a potent myocardial protective effect in the present off-pump CABG model. This method may be clinically feasible and may be able to prolong a safe coronary occlusion.

Early deterioration followed by improvement in contractility during dobutamine stress echocardiography: An unusual response

In 2 patients with severe proximal coronary artery stenosis and normal wall motion in this territory, we observed marked wall motion abnormalities with low and intermediate doses of dobutamine, followed by marked improvement with continued dobutamine infusion. This unusual response suggests ischemic preconditioning and recruitment of coronary collaterals and would be recognized only by monitoring of images obtained at all stages of dobutamine infusion.

Ischemic preconditioning does not acutely improve load-insensitive parameters of contractility in in vivo stunned porcine myocardium

OBJECTIVE

Ischemic preconditioning has been shown to have no beneficial effect on segment shortening in in vivo regionally stunned myocardium. The purpose of this study was to determine whether ischemic preconditioning improves the recovery of postischemic ventricular function when contractility is assessed by load-insensitive measurements including end-systolic pressure length relations, preload recruitable stroke work, and preload recruitable stroke work area in in vivo regionally stunned porcine myocardium.

METHODS

Open chest, pentobarbital-anesthetized pigs were used. Regional ventricular function was monitored by measurements of segment shortening, stroke work, end systolic pressure length relations, preload recruitable stroke work, and preload recruitable stroke work area. The control group was submitted to 15 minutes of left anterior descending coronary artery occlusion and 3 hours of reperfusion. The preconditioned group underwent 2 cycles of 5-minute left anterior descending coronary artery occlusion and 10-minute reperfusion before 15 minutes of occlusion.

RESULTS

There was no infarct in either group. The preconditioning protocol significantly depressed preischemic segment shortening but not regional stroke work. Ischemic preconditioning had no significant beneficial effect on regional stroke work, end-systolic pressure length relations, preload recruitable stroke work, or preload recruitable stroke work area.

CONCLUSIONS

These results confirm that ischemic preconditioning does not ameliorate in vivo porcine myocardial stunning and indicate that ischemic preconditioning may have a limited cardioprotective role during cardiac operation.