Effect of preocclusion stenosis severity on heart rate reactions to coronary occlusion

Spectral analysis related to bare-metal and drug-eluting coronary stent implantation

BACKGROUND

The autonomic nervous system plays a central role in cardiovascular regulation; sympathetic activation occurs during myocardial ischemia.

OBJECTIVE

To assess the spectral analysis of heart rate variability during stent implantation, comparing the types of stent.

METHODS

This study assessed 61 patients (mean age, 64.0 years; 35 men) with ischemic heart disease and indication for stenting. Stent implantation was performed under Holter monitoring to record the spectral analysis of heart rate variability (Fourier transform), measuring the low-frequency (LF) and high-frequency (HF) components, and the LF/HF ratio before and during the procedure.

RESULTS

Bare-metal stent was implanted in 34 patients, while the others received drug-eluting stents. The right coronary artery was approached in 21 patients, the left anterior descending, in 28, and the circumflex, in 9. As compared with the pre-stenting period, all patients showed an increase in LF and HF during stent implantation (658 versus 185 ms2, p = 0.00; 322 versus 121, p = 0.00, respectively), with no change in LF/HF. During stent implantation, LF was 864 ms2 in patients with bare-metal stents, and 398 ms2 in those with drug-eluting stents (p = 0.00). The spectral analysis of heart rate variability showed no association with diabetes mellitus, family history, clinical presentation, beta-blockers, age, and vessel or its segment.

CONCLUSIONS

Stent implantation resulted in concomitant sympathetic and vagal activations. Diabetes mellitus, use of beta-blockers, and the vessel approached showed no influence on the spectral analysis of heart rate variability. Sympathetic activation was lower during the implantation of drug-eluting stents.

Multiple Factor Analysis of the Autonomous Nervous System during PTCA

This study describes the Autonomic Nervous System (ANS) response before, during and after a percutaneous transluminal coronary angioplasty (PTCA). The study population consisted of 37 patients undergoing PTCA from Staff-3 Database. Classical Heart rate variability (HRV) parameters: RR mean, SD, rMSSD, LF, HF, LF/HF and LF/(HF+LF) were extracted and a multiple factorial analysis (MFA) was carried out. Preliminary results show that sympathetic activity increases during and after PTCA, and global HRV decreases during PTCA and increases after PTCA. These findings suggest that MFA provides a powerful tool allowing assessment of ANS's response during PTCA.

Autonomic mechanisms and sudden death after abrupt coronary occlusion

In spite of recent advances in secondary prevention, sudden cardiac death has remained a major public health problem as the majority of fatalities occur in subjects without a history of severe heart disease. Abrupt rupture of a vulnerable plaque resulting in thrombotic occlusion of a coronary artery is a common cause of sudden death in this population. Coronary occlusion does not, however, invariably lead to sudden death but may cause acute myocardial infarction or exacerbation of chest pain. Extensive studies in experimental animals and increasing clinical evidence indicate that autonomic nervous activity has a significant role in modifying the clinical outcome. Sympathetic hyperactivity favours the genesis of life-threatening ventricular tachyarrhythmias while vagal activation exerts an antifibrillatory effect. Strong afferent stimuli from the ischaemic myocardium impair arterial baroreflex and may lead to dangerous haemodynamic instability. Studies with a human angioplasty model have shown that there is wide interindividual variation in the type and severity of autonomic reactions during the early phase of abrupt coronary occlusion, a critical period for out-of-hospital cardiac arrest. The site of the occlusion is not a significant determinant of the reactions, whereas the severity of a coronary stenosis, adaptation or ischaemic preconditioning, beta-blockade and gender seem to affect the autonomic reactions and occurrence of complex ventricular arrhythmias. Clinical and angiographic factors are, however, poor predictors of autonomic reactions in an individual patient. Recent studies have documented a hereditary component for autonomic function, and genetic factors may also modify the clinical manifestations of acute coronary occlusion.

Gender difference in autonomic and hemodynamic reactions to abrupt coronary occlusion

OBJECTIVES

We sought to determine whether there are gender-related differences in autonomic and hemodynamic responses to abrupt coronary occlusion.

BACKGROUND

The risk of sudden death before hospital admission is higher in men with an acute myocardial infarction. The reasons for this gender-related difference are not well understood. Cardiovascular autonomic regulation modifies the outcome of acute coronary events, and there are gender differences in the autonomic regulation of heart rate (HR) in normal physiologic circumstances.

METHODS

We analyzed the changes in HR, HR variability and blood pressure and the occurrence of ventricular ectopic beats during a 2-min coronary occlusion in 140 men and 65 women referred for single-vessel coronary angioplasty. The ranges of nonspecific responses were determined by analyzing a control group of 19 patients with no ischemia during a 2-min balloon inflation in a totally occluded coronary artery.

RESULTS

Women more often had ST segment changes (p < 0.01) and chest pain (p < 0.05) during the occlusion. Significant bradycardia or increase in HR variability as a sign of vagal activation occurred more often in women than in men (31% vs. 13%, p < 0.01 and 25% vs. 11%, p < 0.05, respectively). Coronary occlusion also more often caused (28% vs. 11%, p < 0.01) a decrease in blood pressure in women. The most pronounced female preponderance was in the incidence of Bezold-Jarisch-type reaction (i.e., simultaneous bradycardia and decrease in blood pressure [16% vs. 0.7%, p < 0.0001]). Logistic regression models developed to analyze the significance of gender while controlling for baseline variables and signs of ischemia identified female gender to be an independent predictor of bradycardic reactions (odds ratio [OR] 3.2, 95% confidence interval [CI] 1.4 to 7.7, p < 0.01), hypotensive reactions (OR 2.6, 95% CI 1.1 to 6.0, p < 0.05) and Bezold-Jarisch-type response (OR 22.2, 95% CI 2.5 to 200, p < 0.01). Significance of female gender as a protector against early coronary occlusion-induced ventricular ectopic beats emerged as having borderline significance (OR 0.4, CI 0.1 to 1.1, p = 0.07).

CONCLUSIONS

Vagal activation is more common in women than in men during abrupt coronary occlusion and may have beneficial antiarrhythmic effects, modifying the outcome of acute coronary events.

Effects of trimetazidine on heart rate variability and left ventricular systolic performance in patients with coronary artery disease after percutaneous transluminal angioplasty

Fifty-one patients (mean age 51.6 +/- 7.1 years) with angiographically proven coronary artery disease (CAD) entered the study. In 26 patients (Group I), trimetazidine treatment started twenty-four hours after percutaneous transluminal coronary angioplasty (PTCA). Another 25 patients (Group II) without trimetazidine treatment were kept as controls. The groups were comparable by age, gender, risk factors of CAD, coronary anatomy, left ventricular performance, and heart rate variability indices at baseline state. Power spectral analysis of heart rate variability and two-dimensional and Doppler echocardiographic examinations were performed before PTCA, and twenty-four hours, ten days, thirty days, and three months after PTCA. A statistically significant improvement of left ventricular systolic performance (P < 0.001), augmentation of the parasympathetic band of heart rate variability (P < 0.001), and decline of P1/P2 ratio (P < 0.01) were evident in patients treated with trimetazidine, while no apparent changes were observed in controls. The intergroup analysis also showed marked difference between groups as recorded on the day 30 and month 3 of observation (P < 0.001). During follow-up period recurrences of angina pectoris and ischemia were registered in Group II, while no evidence of ischemia was discerned in Group I patients. In conclusion, trimetazidine modulates the autonomic control of heart rate, ie, reduces sympathetic overactivity and augments vagal influences, improves left ventricular contractility, and diminishes the clinical manifestations of ischemia in patients with CAD after PTCA.

Antiarrhythmic effect of repeated coronary occlusion during balloon angioplasty

OBJECTIVES

The purpose of the present study was to assess whether brief, repeated coronary artery occlusions during balloon angioplasty protect against ischemia-induced ventricular ectopy.

BACKGROUND

Most sudden cardiac deaths are caused by fatal ventricular arrhythmias precipitated by early myocardial ischemia of acute coronary occlusion. In animals, a preceding 3- to 5-min coronary occlusion protects against malignant ventricular arrhythmias during a subsequent prolonged coronary occlusion. Whether such an antiarrhythmic effect caused by ischemic preconditioning occurs in humans is not known.

METHODS

To assess the effects of a preceding, brief vessel occlusion-reperfusion cycle on the occurrence of ventricular ectopy, continuous electrocardiographic, heart rate and blood pressure recordings were performed in 156 patients before and during two identical balloon occlusions of a coronary artery (mean 111 s) separated by a 5-min equilibration period.

RESULTS

The occluded vessel was the left anterior descending coronary artery in 94 patients, the left circumflex branch in 29 patients and the right coronary artery in 33 patients. Balloon occlusion of a coronary artery caused ventricular ectopy in 24 patients. The incidence of ventricular ectopy was higher during the first occlusion than during the second occlusion (21 patients [13.5%] vs. 11 patients [7%], p = 0.02). In 13 patients, ventricular ectopy was observed only during the first occlusion; in 8 patients during both occlusions; and in 3 patients only during the second occlusion. Bigeminal or repetitive ectopic beats were observed in eight patients during the first coronary occlusion and in four patients during the second occlusion. Atrial premature beats occurred during the first occlusion in three patients, but in none of the patients during the second occlusion. The 24 patients with ventricular ectopy during coronary occlusion had milder stenosis than the rest of the patients (mean [+/- SD] 74 +/- 12% vs. 81 +/- 12%, p = 0.01). The 13 patients with ventricular ectopy only during the first occlusion did not, however, differ significantly with respect to any clinical or angiographic features from the rest of the patients with ventricular ectopy. There were no significant differences in the signs of myocardial ischemia or hemodynamic variables between the sequential occlusions.

CONCLUSIONS

A preceding, short vessel occlusion-reperfusion cycle seems to increase the electrical stability of ischemic myocardium.

Effect of beta blockade on heart rate variability during vessel occlusion at the time of coronary angioplasty

Beta blockers modify cardiovascular neural regulation, which may contribute to their protective effect against sudden cardiac death. To evaluate the effects of beta blockade on cardiovascular autonomic reactions caused by acute coronary occlusion in humans, heart rate (HR) variability was analyzed in the time and frequency domains immediately before and during balloon occlusion of a coronary artery in 116 patients randomly assigned to either chronic beta-blocker therapy (beta-blocker group) or no beta blockade (control group) during elective 1-vessel coronary angioplasty. Coronary occlusion (mean 112 seconds) caused a significant increase in both the high- and low-frequency components of HR variability in the control group (n = 58), from 2.7 +/- 1.6 to 3.4 +/- 1.7 (logarithmic units, p < 0.001) and from 4.3 +/- 1.3 to 4.8 +/- 1.5 (p < 0.01), respectively, whereas in the beta-blocker group (n = 58), the high-frequency power did not change during occlusion, but the low-frequency power increased from 3.9 +/- 1.4 to 4.4 +/- 1.4 (p = 0.01). Changes in high- and low-frequency components and HR were related to the change in systolic blood pressure during occlusion in the beta-blocker group (r = 0.53, p < 0.001; r = 0.34, p < 0.05; and r = -0.41, p < 0.01, respectively), but not in the control group (r = -0.17, r = -0.14, and r = 0.24, respectively). Thus, beta blockade attenuates the initial vagal activation associated with acute coronary occlusion and seems to maintain baroreflex-mediated cardiovascular control. The maintained integrity of baroreflex regulation and the alleviation of extreme autonomic reactions during beta blockade may modify the clinical outcome of acute coronary occlusion in a beneficial way.

Stenosis severity and the occurrence of ventricular ectopic activity during acute coronary occlusion during balloon angioplasty

To elucidate the incidence and determinants of early ventricular arrhythmias (VA) during acute coronary occlusion, continuous electrocardiographic, heart rate, and blood pressure recordings were performed in 152 patients during standardized balloon occlusions of significant (50% to 95%) coronary artery stenoses. A control group of 13 patients with chronic total occlusion of a coronary artery was also studied. None of them developed VA during balloon inflation in the preexisting total occlusion of the artery. Balloon occlusion of a coronary artery was associated with occurrence of ventricular ectopy in 18 patients (VA group, 12%). The VA group had milder stenosis severity (72% vs 81%, p < 0.001) than the rest of the patients, and none of them had visible collaterals to the occluded vessel. The VA group also had ST-segment deviations more often (p < 0.05) during occlusion than patients with no VA. Occlusion of the left anterior descending artery caused VA more often (p < 0.05) than occlusion of the left circumflex or right coronary artery. No clinical or hemodynamic variable or medication was associated with the occurrence of VA. In stepwise logistic regression analysis, the only significant predictors of ventricular ectopic activity were the stenosis severity and the anterior site of coronary occlusion. Even a nonstenotic plaque can be so fragile that it is prone to rupture. The present findings suggest that such an occlusion may result in electrical instability more easily than occlusion of a more advanced coronary lesion.

Heart rate variability during repeated arterial occlusion in coronary angioplasty

Acute coronary occlusion may cause severe autonomic reactions that can modify the clinical presentation of acute ischemic events. To evaluate whether adaptation in these autonomic reactions exists during repeated short coronary occlusions, heart rate (HR) and its variability in the time and frequency domains were analyzed in 70 patients with significant (50% to 95%) coronary artery stenosis immediately before and during 2 identical balloon occlusions of the vessel (mean 110 seconds). Reactions were compared with the range of nonspecific changes formed by analyzing a control group (n = 13) with no ischemia during balloon inflation in a totally occluded coronary artery. Thus, neither occlusion caused significant changes in HR or HR variability in 29 patients (41%). Vagal activation, as seen by an abnormal increase in HR variability or bradycardia, or both, was observed in 24 patients (34%). HR reactions in this group (p < 0.05) were significantly attenuated during the second occlusion. An opposite reaction (i.e., abnormal decrease in HR variability or tachycardia, or both) was observed in 17 patients (24%). A nonsignificant tendency for attenuation of the reactions was also seen in this group. Severity of chest pain, frequency of ST-segment shifts, or narrowing of pulse pressure were comparable during the 2 occlusions. Thus, a preceding short vessel occlusion-reperfusion cycle seems to attenuate autonomic HR reactions, especially vagal reactions, during subsequent coronary occlusion. Alleviation of extreme autonomic reactions may modify the clinical outcome of coronary occlusion in a beneficial way.