Ischemia-induced changes in human endocardial electrograms during percutaneous transluminal coronary angioplasty

Effect of balloon inflation-induced acute ischemia on QT dispersion during percutaneous transluminal coronary angioplasty

BACKGROUND

QT dispersion (QTd = QTmax-QTmin) measured as interlead variability of QT interval reflects the spatial inhomogeneity of ventricular repolarization times, and increased QTd may provide a substrate for malignant ventricular arrhythmias. Ischemia is associated with regional abnormalities of conduction and repolarization.

HYPOTHESIS

This study aimed to investigate the effect of acute ischemia on QTd during successful percutaneous transluminal coronary angioplasty (PTCA).

METHODS

Forty-three patients (10 women, 33 men, mean age 56 years) were enrolled in the study. Electrocardiogram (ECG) recordings were taken before PTCA and during balloon inflation period. QT maximum (QTmax), QT minimum (QTmin), and QTd (QTmax-QTmin) values were calculated from the surface ECG.

RESULTS

There was no difference among QTmax values (p = 0.6). Mean QTmin during balloon inflation was lower than before PTCA (368 +/- 45 vs. 380 +/- 41 ms, p = 0.002). The difference between QTd values before and during balloon inflation was statistically important (65 +/- 9 vs. 76 +/- 10 ms, p = 0.001). This difference is caused by a decrease in QTmin during balloon inflation.

CONCLUSION

Acute reversible myocardial ischemia induced by balloon inflation causes an increase in QTd value, and this increment is the result of a decrease in QTmin interval. Therefore, QTd may be a marker of reversible myocardial ischemia.

Effect of ischemia on implantable defibrillator intracardiac shock electrograms

INTRODUCTION

Few attempts have been made to extract information from the ventricular electrogram (EGM) recorded by implantable cardioverter defibrillators (ICD) aside from the discrimination of supraventricular tachycardia and ventricular tachycardia. The current study aims to examine the effect of ischemia in the major coronary artery distributions on the shock EGM from ICDs.

METHODS

Domestic crossbred pigs (n = 10, 20-40 kg) were implanted with a dual-coil right ventricular defibrillation system. Through the femoral approach, percutaneous balloon occlusion of the major coronary arteries was performed. The left anterior descending (LAD), left circumflex (LCx), and right coronary (RCA) arteries were occluded in random order for 3-5 minutes with 30-minute periods of reperfusion in between and the shock EGMs were recorded and analyzed.

RESULTS

During peak ischemia, R wave amplitude increased by a mean of 204.3% (P = 0.003), increased by a mean of 73.8% (P = 0.0009), and decreased by a mean of 28.0% (P = 0.109) in the LAD, LCx, and RCA territories, respectively. During peak ischemia ST segments elevated by a mean of 105.3% (P = 0.041), elevated by a mean of 114.9% (P = 0.064), and decreased by a mean of 584.5% (P = 0.006) in the LAD, LCx, and RCA territories, respectively.

CONCLUSIONS

Ischemia affects ICD shock EGMs in a manner that appears to vary depending on the culprit vessel. Our data demonstrate the feasibility of ischemia detection from ICD shock EGMs.

Repeated Balloon Inflations Do Not Diminish ST Segment Elevation even though Coronary Collateral Recruitment Is Promoted in Pigs

OBJECTIVE

Attempts to demonstrate preconditioning during repeated angioplasty balloon inflations (BIs) have not been universally successful. The main obstacle is that the first BI is unreliable, due to the variable degrees of occlusion by the deflated balloon. In the present study, we examined whether ST segment elevation decreases and evaluated its relation to collateral recruitment during repeated angioplasty BIs in the pig.

METHODS AND RESULTS

Twenty male pigs, 7 months old, under general anesthesia, underwent 3 repeated BIs of 120 s, with a 5-min interval between them, in the left anterior descending artery or the right coronary artery. A pressure wave wire was used for the measurement of coronary wedge pressure and to obtain the intracoronary ST segment elevation. Intracoronary ST segment elevation was 1.97 +/- 0.76 mV during the 1st BI, 2.09 +/- 0.82 mV during the 2nd BI and 1.84 +/- 0.82 mV during the 3rd BI (p = n.s.). Coronary wedge pressure was 12 +/- 6, 18 +/- 18 and 20 +/- 20 mm Hg (p < 0.05 vs. 1st BI) during the 3 BIs, respectively.

CONCLUSION

Repeated BIs do not diminish ST segment elevation in the pig model, even though coronary collateral recruitment is promoted.

Evaluation of ischemic injury of the cardiac tissue by using the principal component analysis of an epicardial electrogram

Monitoring and control of the heart tissue viability is of crucial importance during heart surgery operations. In most cases the heart tissue suffers from an ischemic injury that causes a decrease in the velocity of electrical excitation propagation in it and influences the shape of the excitation wave front that spreads over the injured area. It is reflected in a more complex shape of the registered epicardial electrogram as compared to normal. A method for quantitative evaluation of the complexity of the shape of the epicardial electrogram based on the principal component analysis is here proposed for evaluation of the ischemic injury of the cardiac tissue. A minimal, yet sufficient, number of the principal components (the optimal basis functions) for truncated expansion of the epicardial electrogram signals could be used as an estimate of signal complexity. The method for determination of such a minimal, yet sufficient, number of principal components were developed by using epicardial electrograms registered during in situ experiments on dogs in which local ischemia was evoked by ligation of a coronary vessel.

Heart tissue viability monitoring in vivo by using combined fluorescence, thermography and electrical activity measurements

A prototype system for in vivo monitoring of the heart tissue viability by using combined measurements of fluorescence, thermography and electrical activity has been elaborated for cardiac surgery. The fluorescence imaging of nicotinamide adenine dinucleotide NAD(P)H in the blue light range (lambda=467 nm) by using UV light (lambda=347 nm) excitation was used to detect metabolic disturbances. The method of the principal component analysis was used for the processing of the fluorescence image sequences. Far infrared (lambda=7.5-13 microm) imaging was used to evaluate temperature dynamics of the tissue surface during circulation disturbances. Evaluation of the epicardial electrogram shape by using continuous wavelet transform was used to detect and evaluate ischemia-caused disturbances of the electrical activity of the tissue. The combination of temperature, fluorescence and electrical activity estimates obtained from synchronically registered parameters during the experiments on model systems and experimental animals yielded qualitatively new results for the evaluation of cardiac tissue viability and enabled to achieve a versatile evaluation of the heart tissue viability.

Frequency and clinical significance of ischemic preconditioning during percutaneous coronary intervention

OBJECTIVES

We sought to examine the short- and long-term clinical consequences of ischemic preconditioning (IP) during percutaneous coronary intervention (PCI).

BACKGROUND

Ischemic preconditioning has been demonstrated in animal models to significantly diminish the extent of myocardial necrosis consequent to coronary occlusion. Surrogate markers of ischemic injury (ST segment shift, lactate release, creatine kinase release) in humans have been shown to be similarly diminished with IP elicited during PCI. There are no studies of the frequency of inducibility of IP during PCI, nor are there longer-term data on the clinical relevance of IP.

METHODS

A total of 382 patients underwent elective PCI employing a previously validated protocol to elicit IP. Procedural, in-hospital, and one-year outcomes were recorded.

RESULTS

Ischemic preconditioning was elicited in 80% of patients and was associated with a significant reduction in the likelihood of in-hospital adverse cardiac events (IP group, 12.1%; non-IP group, 44.1%; p < 0.0001). Women and diabetic patients were less likely to exhibit IP. By one year, patients failing to manifest IP were at significantly greater risk of post-discharge death or non-fatal myocardial infarction (MI) (non-IP group, 25.9%; IP group, 11.1%; p < 0.002). Failure to manifest IP was significantly and independently associated with an increased risk of death or non-fatal MI by one year.

CONCLUSIONS

Clinically relevant short- and long-term cardioprotection can be found in association with IP during PCI. In-hospital adverse ischemic events are significantly diminished in patients with IP, as are the risks of death or non-fatal MI at one year. Failure to elicit IP during PCI serves as an independent marker of increased risk of future ischemic events.

Characterisation of acute myocardial ischaemia in a canine model based on principal component analysis of unipolar endocardial electrograms

The study presents a method for identifying endocardial electrical features relevant to local ischaemia detection at rest. The method consists of, first, normalisation of electrograms to a uniform representation; secondly, the use of principal component analysis to reduce the dimensionality of the electrogram vector space; and, thirdly, a search for a classification axis that matches the degree of ischaemia present in the tissue. Left ventricular myocardial states were assessed by echocardiography and NOGA mapping in eight dogs at baseline and then immediately after, 5h after and 3 days after occlusion of the left anterior descending coronary artery. Five principal components were required to approximate electrograms with an average error of less than 10% of the peak-to-peak amplitude. Correlations of 0.77, 0.80 and 0.84 were obtained between the principal component-based parameters and the echocardiography scores at the three ischaemic stages, respectively. Expression of these parameters in the time domain showed that the major changes occurred in the depolarisation segment of the endocardial electrogram as well as in the ST-segment. In conclusion, the proposed method provides a suitable alternative co-ordinate system for the classification of ischaemic regions and highlights signal segments that change as a result of pathology.

Reduced albumin-cobalt binding with transient myocardial ischemia after elective percutaneous transluminal coronary angioplasty: a preliminary comparison to creatine kinase-MB, myoglobin, and troponin I

BACKGROUND

Previous reports suggest that ischemic conditions rapidly reduce the capacity of human albumin to bind exogenous cobalt. A new assay based on human albumin-cobalt binding (ACB) may help detect early myocardial ischemia. We investigated altered ACB during the first 24 hours after transient ischemia induced during elective percutaneous transluminal coronary angioplasty (PTCA). We then compared ACB assay results with creatine kinase isoenzyme (CK-MB), myoglobin, and cardiac troponin I (cTn-I) values after PTCA.

METHODS AND RESULTS

In 41 patients undergoing elective PTCA, plasma samples were tested for the ACB assay, CK-MB, myoglobin, and cTn-I before, immediately after, and 6 and 24 hours after PTCA. Thirteen additional patients served as a control group with albumin-cobalt assays performed before and after diagnostic coronary catheterization without angioplasty. ACB assay results demonstrated a significant mean percent difference (10.1%) immediately after PTCA compared with baseline (P < .000001) and returned to baseline by 6 hours after PTCA. ACB assay differences immediately after PTCA were significantly greater than in the control group (10.1% vs -0.9%, P < .001). Mean CK-MB, myoglobin, and cTn-I values were not elevated above baseline immediately after PTCA but were significantly elevated above baseline 6 and 24 hours after PTCA.

CONCLUSIONS

These preliminary results suggest that human albumin undergoes a significant reduction in its capacity to bind exogenous cobalt soon after transient coronary occlusion during human PTCA and before significant elevations of CK-MB, myoglobin, or cTn-I. Further confirmatory investigations are warranted to determine if the ACB assay is a useful diagnostic test for early myocardial ischemia.

Comparison of endocardial electromechanical mapping with radionuclide perfusion imaging to assess myocardial viability and severity of myocardial ischemia in angina pectoris

The assessment of left ventricular electromechanical activity using a novel, nonfluoroscopic 3-dimensional mapping system demonstrates considerable differences in electrical and mechanical activities within regions of myocardial infarction or ischemia. We sought to determine whether these changes correlate with indexes of myocardial perfusion, viability, or ischemia. A 12-segment comparative analysis was performed in 61 patients (45 men, 61 +/- 12 years old) with class III to IV angina, having reversible and/or fixed myocardial perfusion defects on single-photon emission computed tomographic perfusion imaging. A dual-isotope protocol was used, consisting of rest and 4-hour redistribution thallium images followed by adenosine technetium-99m sestamibi imaging. Average rest endocardial unipolar voltage (UpV) and local shortening (LS) mapping values were compared with visually derived perfusion scores. There was gradual and proportional reduction in regional UpV and LS in relation to thallium-201 uptake score at rest (p = 0.0001 and p = 0.0002, respectively) and redistribution studies (p = 0.0001 and p = 0.003, respectively). UpV > or = 7.4 mV and LS > or = 5.0% had a sensitivity of 78% and 65%, respectively, with a specificity of 68% and 67% for detecting viable myocardium. UpV values of 12.3 and 5.4 mV had 90% specificity and sensitivity, respectively, to predict viable tissue. UpV, but not LS, values differentiated between normal segments and those with adenosine-induced severe perfusion defects (11.8 +/- 5.3 vs 8.8 +/- 4.1 mV, p = 0.005). Catheter-based left ventricular assessment of electromechanical activity correlates with the degree of single-photon emission computed tomographic perfusion abnormality and can identify myocardial viability with a greater accuracy than myocardial ischemia.

Beneficial impact of preconditioning during PTCA on creatine kinase release

BACKGROUND

Previous studies in humans have indicated that there is less ischemic dysfunction during PTCA when ischemic preconditioning is elicited. However, the clinical relevance of these observations remains unclear. The present study design tests the hypothesis that PTCA performed to elicit the preconditioning response would result in less myocardial necrosis as assessed by postprocedure creatine kinase (CK) levels.

METHODS AND RESULTS

Patients (n=150) undergoing PTCA for unstable ischemic syndromes were randomly assigned to receive a previously validated approach to PTCA-mediated preconditioning (PC) or an unrestricted approach to balloon angioplasty (UC). CK levels were determined at 8, 12, and, if necessary, 24 hours. Clinical success rates were equivalent for the 2 groups. However, the frequency of any CK elevation was significantly higher in the UC group (25%) than in the PC group (7. 1%) (P<0.005). Multivariable analysis confirmed a significant effect of preconditioning on CK release.

CONCLUSIONS

A standardized protocol to elicit preconditioning during PTCA results in a significant reduction in the rate of CK elevation in a high-risk population. These observations support the clinical relevance of ischemic preconditioning in humans.

Usefulness of endocoronary electrocardiogram in the detection of myocardial viability and comparison with single-photon emission computed tomography Tl-201

In 20 patients who had recently had an acute myocardial infarction, we compared endocoronary electrocardiographic modifications recorded during angioplasty with thallium-201 for the detection of myocardial viability. Our data demonstrate that endocoronary electrocardiography can be an easy and reliable tool to assess viability, with sensitivity, specificity, and positive and negative predictive values of 100%, 80%, 94%, 100%, respectively.

Effect of time interval between two balloon inflations on ischemic preconditioning during coronary angioplasty

Ischemic preconditioning, defined as a reduction in myocardial ischemia caused by repeated brief episodes of coronary occlusions, is observed during percutaneous transluminal balloon angioplasty (PTCA). To elucidate the effects of the length of the interval between consecutive balloon inflations on ischemic preconditioning during PTCA, we examined 62 patients with chronic stable angina (48 males and 14 females; mean age 62 +/- 10 yr). PTCA was performed on the left anterior descending artery lacking in collateral vessels. A 2-min balloon inflation was performed twice and the extent of ST segment elevation in the electrocardiogram and the severity of chest pain (scored from 0 to 10) for each inflation were determined and compared. Patients were divided into three groups according to the interval between the two inflations: 1 min, Group 1; 2 min, Group 2; and 5 min, Group 5. In Groups 2 and 5, ST-segment elevation was significantly decreased during the second balloon inflation, as compared with that during the first inflation (P < 0.01, P < 0.001). A significant decrease was also observed in the severity of chest pain (P < 0.05, P < 0.01). However, Group 1 showed no significant decrease in ST-segment elevation or severity of chest pain between the first and second inflations. ST-segment elevation and chest pain were reduced to a greater extent in Group 5 than in Group 2. Results suggest that an interval of more than 2 min between balloon inflations is required to achieve ischemic preconditioning during PTCA.