Improvement of risk-stratification by use of a new combination of Holter variables in survivors of myocardial infarction

OBJECTIVE: Holter monitoring is one option in risk-stratification after acute myocardial infarction (MI). Measurements of heart rate variability (HRV), ventricular tachycardia (VT) and ST-segment elevation (ST upward arrow ) have been useful in predicting clinical outcome. We investigated if a combination of different Holter variables could optimize risk-stratification. DESIGN: One hundred and twenty-one men < 70 years old with a first MI were studied. Holter monitoring for 24 h was started 11 +/- 5 days after MI and analysed for HRV, VT and ST. Follow-up was 10-12 years with cardiac death as endpoint. RESULTS: Thirty-six patients were positive for > or = 1 Holter variable (HRV in 15, VT in 16, ST in 10). At follow-up 22 cardiac deaths had occurred. The prognostic sensitivity of individual Holter variables ranged from 23 to 36%, but increased to 64% if combined. The cardiac death rate in Holter positive patients (39%) was significantly higher than in Holter negative patients (9%) (p < 0.0001). CONCLUSION: By combining measurements of HRV, VT and ST the prognostic importance of Holter monitoring can be significantly improved. The patients can be stratified in a low-risk group with an annual mortality < 1% vs a high-risk group with a cardiac death rate around 40% over the following decade.     

Heart rate variability is decreased in chronic kidney disease but may improve with hemoglobin normalization

BACKGROUND: Cardiac autonomic function can be measured by heart rate variability (HRV). Dialysis patients have an abnormally low HRV and are at increased risk for sudden death. A reduction in HRV is associated with anemia. HRV was therefore measured in patients with chronic kidney disease (CKD) after hemoglobin normalization. METHODS: Sixteen nondiabetic patients with CKD stage 4 (glomerular filtration rate 23.7 +/- 13.9 ml/min) and renal anemia received epoetin aiming at a hemoglobin level of 135-150 g/L. HRV was measured by 24-hour Holter electrocardiogram at baseline and after hemoglobin normalization and in a reference group consisting of 16 volunteers without impairment of renal function. RESULTS: Hemoglobin level increased from 100.7 +/- 12.6 g/L to 142.4 +/- 7.2 g/L during the study. At baseline, HRV measured in the time domain as the standard deviation of all normal RR intervals in the entire 24-hour electrocardiogram (SDNN) was 116.3 +/- 39.2 ms compared with 147.5 +/- 27.2 ms in the reference group (p<0.05). The frequency domain measures low-frequency power and total power were 367.7 +/- 350.2 ms2 and 1,368.9 +/- 957.4 ms2 compared with 717.3 +/- 484.5 ms2 and 2,228.3 +/- 1142.4 ms2 (p<0.05) in the reference group. After hemoglobin normalization there was an increase in low-frequency power to 498.3 +/- 432.7 ms2 (p<0.05) and in total power to 1,731.0 +/- 1,069.4 ms2 (p<0.05) while SDNN remained at 120.9 +/- 33.8 ms (p=ns). CONCLUSIONS: CKD patients not yet on dialysis had a reduced HRV, indicating impaired autonomic function, compared with a reference group without impaired renal function. Hemoglobin normalization improved but did not fully normalize HRV. The clinical significance of this deserves further investigation.     

Recovery of autonomic nervous activity after myocardial infarction demonstrated by short-term measurements of SDNN

OBJECTIVE: Heart rate variability (HRV) has been demonstrated to be a risk factor after acute myocardial infarction (AMI). In the present study serial measurement of SDNN (standard deviation of the mean of qualified NN-interval) in short intervals was used to assess HRV changes after AMI, and determine the role of these as independent risk factors compared to clinical, arrhythmic, ischemic and anamnestic variables. Measurements from a normal healthy middle-aged male population were used as reference (n = 63). METHODS: SDNN from a five-minute period during day and night-time, respectively, was examined in 103 patients 1 week (n = 54), 1 month (n = 72) and 12-16 months (n = 54) after infarction. RESULTS: Day SDNN did not change during one-and-a-half years after AMI, and was significantly reduced compared with healthy males. Night SDNN, low after 1 week, with recovery 1 month after AMI, was significantly reduced compared with healthy males early, but not late after AMI. Thus, the study indicated during day-time a continuous abnormal sympathetic preponderance in the course of 16 months after AMI, and during night-time a gradual recovery of parasympathetic preponderance beginning early after AMI. CONCLUSION: One week after AMI day-time SDNN of <30 ms, and night-time SDNN of < 18 ms, age > or =60 years, and myocardial ischemia (Holter monitoring) were independent predictors of 9 years' mortality. One and 12-16 months after AMI reduced day and night-time SDNN had no prognostic implication.     

Improvement of Risk-stratification by Use of a New Combination of Holter Variables in Survivors of Myocardial Infarction

Objective: Holter monitoring is one option in risk-stratification after acute myocardial infarction (MI). Measurements of heart rate variability (HRV), ventricular tachycardia (VT) and ST-segment elevation (ST &#78 ) have been useful in predicting clinical outcome. We investigated if a combination of different Holter variables could optimize risk-stratification. Design: One hundred and twenty-one men < 70 years old with a first MI were studied. Holter monitoring for 24 h was started 11 &#45 5 days after MI and analysed for HRV, VT and ST &#78 . Follow-up was 10-12 years with cardiac death as endpoint. Results: Thirty-six patients were positive for &#83 1 Holter variable (HRV in 15, VT in 16, ST &#78 in 10). At follow-up 22 cardiac deaths had occurred. The prognostic sensitivity of individual Holter variables ranged from 23 to 36%, but increased to 64% if combined. The cardiac death rate in Holter positive patients (39%) was significantly higher than in Holter negative patients (9%) ( p < 0.0001). Conclusion: By combining measurements of HRV, VT and ST &#78 the prognostic importance of Holter monitoring can be significantly improved. The patients can be stratified in a low-risk group with an annual mortality < 1% vs a high-risk group with a cardiac death rate around 40% over the following decade.     

Influence of ischemia on heart-rate variability in chronic hemodialysis patients

BACKGROUND: Sudden cardiac death occurring in patients with end-stage renal disease (ESRD) may be related to poor autonomic function with a significant decreased heart-rate variability (HRV). In addition, coronary artery disease has a high prevalence in this population and accounts for 50% of deaths. In the present study, relationships between HRV and myocardial ischemic abnormalities revealed by myocardial scintigraphy (MS) were evaluated in 32 chronic hemodialysis patients. METHODS: We prospectively studied 32 chronic hemodialysis patients. Each underwent MS and 24 h electrocardiography at baseline for analysis of time and frequency domain the day of dialysis. Three periods were analyzed: during dialysis session, the morning after (nondialytic period), and in a 24 h period. Patients were included in group 1 (seven women, 11 men; mean age: 62+/-19 years) when MS revealed no ischemia, whereas patients were included in group 2 (seven women, seven men; mean age: 63.1+/-20 years) when MS revealed ischemic lesions. RESULTS: A student+/-test revealed that during the nondialytic period, two important markers of HRV, percentage of delta RR>50 ms (pNN50) (4.5+/-4.04 in group 1 versus 1.7+/-1.4 in group 2), and root mean square of delta RR (rMSSD) (27.7+/-13.4 versus 19.7+/-6.8) were significantly reduced in group 2 compared with values in group 1. No significant difference appears between the two groups for standard deviation of normal to normal intervals (SDNN), mean heart rate, and spectral analysis. CONCLUSION: Patients with ESRD and myocardial ischemia revealed by MS have reduced parasympathetic activity during the nondialytic period. Correlations between parameters of HRV and ischemic lesions revealed by MS have been shown for the first time.     

ST-segment depression and myocardial contractility during Cesarean section under spinal anesthesia

PURPOSE: To evaluate myocardial contractility during ST segment depression in healthy parturients during Cesarean section (CS). METHODS: Forty-seven consecutive term parturients undergoing elective CS under spinal anesthesia were studied. The ST segment was recorded continuously on leads II and V5 using a Holter monitor. Myocardial performance was evaluated by measuring cardiac index (CI), heart rate (HR), pre-ejection period (PEP), ventricular ejection time (VET), systolic time ratio (STR, PEP/VET), and ejection fraction (EF) with an impedance cardiograph. RESULTS: Fourteen patients (30%) developed ST segment depression within 15 min after delivery and the remaining 33 (70%) did not (controls). Seven patients developed a 1 mm change, five patients a 2 mm change and the remaining two a 3 mm change in the ST segment. Compared with pre-anesthesia values, the mean HR increased from 103 +/- 10 to 116 +/- 10 (ISD) bpm (P = 0.001), CI from 4.7 +/- 0.7 to 5.6 +/- 1.7 L.min-1 (P = 0.01), EF from 0.58 +/- 0.08 to 0.66 +/- 0.05 (P = 0.01) and STR decreased from 0.26 +/- 0.06 to 0.2 +/- 0.04 (P = 0.01) during ST segment depression. At this time, CI, HR and EF were greater and STR smaller than values obtained 15 min after delivery in the control subjects. CONCLUSION: ST-segment depression occurring during CS is associated with a hyperkinetic myocardial contractile state.     

Influence of angiotensin converting enzyme inhibitor treatment on cardiac autonomic modulation in patients receiving haemodialysis

BACKGROUND: Cardiovascular disease mortality among patients with end stage renal disease (ESRD) exceeds that which is predicted by traditional risk factors. Sudden death accounts for up to 15-38% of patients with ESRD found dead at home. Heart rate variability (HRV) is a reliable measure of autonomic modulation and has a very strong predictive value for ventricular arrhythmias and sudden death. A lower HRV is associated with increased risk. Modifying autonomic tone pharmacologically reduces death from dysrhythmia in the general population but has not been studied in ESRD. METHODS: We examined the effect of ramipril, an angiotensin converting enzyme inhibitor (ACEI) known in the general population to increase HRV, on cardiac function and heart rate variability in patients with renal failure. Eligible subjects on haemodialysis underwent a 2-week washout period free of ACEI or beta blockers, during which time hypertension was treated with amlodipine, which has been shown not to affect HRV. Haemodynamic and HRV measurements were obtained at baseline and after subjects were treated for 4 weeks with an ACEI. RESULTS: Haemodynamics did not differ at 0 and 4 weeks. Baseline HRV values were markedly below those found in the general population, indicating pronounced predominance of sympathetic tone over vagal tone. Actual worsening of HRV with ACEI treatment was evident in several major time domains. The time domain SDNN (the standard deviation of all normal RR intervals) fell from 42.0 +/- 24.8 ms to 20.1 +/- 16.1 ms (P = 0.004) and the triangulation index fell from 178.0 +/- 94.0 to 115 +/- 59.2 (P = 0.01). A trend toward reduced HRV was seen in several other time domains. CONCLUSION: These findings suggest that, unlike the general population, treatment of ESRD patients with an angiotensin converting enzyme inhibitor may cause a deleterious shift toward increased cardiac sympathetic nervous system tone.     

Electrocardiographic changes during cesarean section under regional anesthesia.

To determine electrocardiographic changes and whether myocardial ischemia occurs during cesarean section, electrocardiograms were recorded continuously using Holter monitoring in 25 patients undergoing elective cesarean section under either spinal or epidural anesthesia. In addition, in 13 of the patients, two-dimensional precordial echocardiography was carried out before and during cesarean section. ST segment depression suggestive of myocardial ischemia occurred in 16 patients including 8 of the 13 with echocardiograms. Wall motion remained entirely normal during episodes of ST segment depression. Patients in whom ST depression developed had significantly more rapid heart rates at delivery than those who did not experience ST depression. We conclude that ST segment depression is a common feature of the electrocardiogram during cesarean section under regional anesthesia and is not the result of myocardial ischemia.     

Perioperative ST-segment depression and troponin T release. Identification of patients with highest risk for myocardial damage

BACKGROUND: Patients undergoing major vascular surgery are at constant risk of developing perioperative myocardial complications, especially myocardial infarction. The following study was performed to answer the question whether ST segment changes, analysed by Holter monitoring and ST segment analysis, are accompanied by release of cardiac troponin T, a highly specific marker of myocardial damage. METHODS: Twenty patients undergoing elective aortic resection were studied by performing Holter ECG, including ST segment analysis, beginning on the evening before surgery until the third postoperative day. Within this period serum levels of cardiac troponin T were determined at 8 timepoints. RESULTS: A total of 8/20 of the patients (40%) showed significant ST depressions (range -0.17/-0.68 mV), without any clinical symptom, with a median of 9 episodes (range 2-24). In 3 of the 8 patients, each with repetitive periods of ST depression, elevated troponin T levels were found (0.45/0.52/1.69 micrograms/l). No troponin T release nor cardiac events were noticed in the remaining patients. No dependency could be found between troponin T release and the magnitude of ST depression or the number of ST depression episodes. CONCLUSION: Haemodynamic changes, oxygen imbalance and stress during major vascular surgery frequently lead to an ischaemic burden, which is indicated by ST segment changes during ECG ST analysis. Longlasting ST depression reaching an individual critical cut-off limit followed by structural myocardial damage may be verified by elevated levels of cardiac troponin T. Prolonged periods of ST depression should be followed by determination of cardiac troponin T.     

Effects of nicardipine and nitroglycerin on perioperative myocardial ischemia in patients undergoing coronary artery bypass surgery.

Perioperative myocardial ischemic episodes are predictive of adverse cardiac outcomes after coronary artery bypass surgery. We compared the efficacy of continuous infusions of nicardipine (group NIC) and nitroglycerin (group NTG) in reducing the frequency and severity of myocardial ischemic episodes. Patients received either a nicardipine infusion, 0.7 to 1.4 microg/kg/min (n = 30), nitroglycerin infusion, 0.5 to 1 microg/kg/min (n = 30), or neither medication (group C; n = 17) after aortic occlusion clamp release and for 24 hours postoperatively. Myocardial ischemic episodes were considered as ST segment depressions or elevations of 1 mm or greater from baseline, each at J + 60 milliseconds and lasting 1 minute or greater, using a two-channel Holter monitor. Only nicardipine significantly decreased the duration (3.2 +/- 1.2 min/h) and the area under the ST time curve (AUC; 5.7 +/- 15.7 AUC/h) of 1-mm or greater myocardial ischemic episodes compared with group C (17.2 +/- 5.6 min/h and 30.1 +/- 49 AUC/h, respectively) during the intraoperative postbypass period. A trend toward lower frequency, duration, and area under the ST time curve of myocardial ischemic episodes was observed in group NIC compared with group NTG. Cardiac indices and mixed venous oxygen saturations were significantly greater, whereas systemic pressures were less in group NIC compared with group NTG for the same period. These results suggest that nicardipine, but not nitroglycerin, decreased the duration and area under the ST time curve of myocardial ischemic episodes shortly after coronary revascularization. Larger studies are required to verify the efficacy of nicardipine in reducing the severity of myocardial ischemia during cardiac surgery.     

Perioperative myocardial ischemia in patients with peripheral arterial occlusive diseases

Patients with peripheral vascular disease (PVD) often have coronary artery disease (CAD) which means an increased risk during anesthesia. The prevalence of CAD is nearly 50% among such patients. Owing to claudication, diagnostic stress tests can rarely be performed in PVD patients. In order to evaluate the frequency of transient perioperative myocardial ischemia, Holter monitoring was performed in 30 consecutive PVD patients with ASA II-III and AVK scale (Fontaine) II-IV who were undergoing femoropopliteal bypass surgery. Patients who had left bundle branch block and left ventricular hypertrophy or were taking digitalis medication were excluded from Holter monitoring. The ST-segment analysis of the frequency modulated recordings (n = 19) revealed episodes of myocardial ischemia in 26% of the patients. Most (75%) of the episodes occurred preoperatively, and 25%, during or after the anesthesia or during preparation for it. Risk factors for CAD were more often found in patients with ST segment alterations than in patients without ST segment deviations, even though the preoperative antianginal medication administered was comparable in the two subgroups. It is concluded that in a considerable subset of PVD patients silent myocardial ischemia occurs, which can be related to the different perioperative intervals by means of ST segment analyses of Holter recordings. The ST segment may allow a better insight into the cardiac state of PVD patients. Further studies are necessary in larger populations to test our suspicion.     

The breakdown of fractal heart rate dynamics predicts prolonged postoperative myocardial ischemia

Patients with myocardial ischemia after noncardiac surgery have a three- to ninefold increased risk of adverse cardiac events. In this study we tested the hypothesis that altered preoperative heart rate variability (HRV) predicts postoperative prolonged myocardial ischemia (>10 min) in elderly surgical patients. Thirty-two patients, age 60 yr or older, admitted to hospital for surgical repair of a traumatic hip fracture with preoperative night and daytime Holter recordings were included. Holter monitoring was initiated at arrival at hospital and continued until the third postoperative morning. Conventional HRV measures along with analysis of short-term fractal scaling exponent (alpha(1)) of RR intervals were assessed for night (from 2 AM to 5 AM) and day (7 AM to 12 AM) periods in each patient. Preoperative alpha(1) was significantly lower (i.e., increased randomness in HRV) during the nighttime compared with daytime (mean +/- SEM; 0.92 +/- 0.08 versus 1.03 +/- 0.06; P = 0.002) in patients with postoperative myocardial ischemia. Patients without ischemia had no such difference. In stepwise multivariate logistic regression analysis, increased preoperative night-day difference of alpha(1) was the only independent predictor of postoperative prolonged ischemia. The odds ratio for an increase of 0.16 U in night-day difference of alpha(1) (corresponding to interquartile range) was 7.7 (95% confidence interval, 1.9-51.4; P = 0.0018). Breakdown of fractal-like heart rate dynamics is predictive for postoperative prolonged myocardial ischemia in elderly patients having emergency surgery for traumatic hip fracture. IMPLICATIONS: Night and daytime Holter recordings before surgical repair of traumatic hip fracture were analyzed with linear and nonlinear heart rate variability methods. Preoperatively increased randomness in heart rate variability was predictive for postoperative, silent prolonged myocardial ischemia. Prolonged myocardial ischemia increases the risk for adverse cardiac events.     

Lack of circadian variation in the activity of the autonomic nervous system after major abdominal operations.

OBJECTIVE: Most sudden postoperative deaths occur during the night and we conjectured that this was associated with circadian variations in the autonomic nervous tone, reflected in heart rate variability. DESIGN: Prospective clinical study. SETTINGS: University hospital, Denmark. SUBJECTS: 44 patients who had had major abdominal operations. INTERVENTIONS: Patients were monitored with 24-hour Holter ECG on the second postoperative day-evening-night. We calculated heart rate variability from the standard deviation of all normal R-R intervals (excluding ectopics-NN intervals) around the mean NN interval for the period of measurement (SDNN), the root mean square of the standard deviation of the differences between NN intervals (RMSSD), the percentage of NN intervals differing by more than 50 msec from adjacent NN intervals (pNN50) and the coefficient of component variance (meanNN/SDNN). MAIN OUTCOME MEASURES: Heart rate and heart rate variability. RESULTS: Circadian variation calculated from the SDNN (p = 0.43) the pNN50 (p = 0.11), the RMSSD (p = 0.47), and mean NN:SDNN ratio (p = 0.13) was absent postoperatively. Circadian variation in the heart rate was present but was set on a higher level compared with reference values. CONCLUSION: After major abdominal operations there was a lack of circadian variation in the autonomic nervous tone.     

II: Perioperative Holter monitoring: clinical relevance and practice

Perioperative, mostly silent ischaemia in patients with coronary heart disease is difficult to detect by clinical examinations. Methods. During the clinical evaluation (part I of this study) we monitored patients with prior myocardial infarction (MI) by continuous electrocardiographic (ECG) recording from the evening before until the first 24?h after operation. Excluded from Holter ECG studies were patients with a bundle branch block, pacemaker, valvular heart disease, cardiomyopathy, severe hypokalaemia, and digitalis treatment. Data were recorded with a Holter 8500 recorder (Marquette Electronics) using modified V2, V4, and V5 leads (Fig. 1). Holter tapes were analysed twice with a Holter computing system (Software 5.8, Marquette Electronics), first by a blinded technician and then by the authors themselves. We defined the following criteria as pathological ST segment changes and as ischaemic episodes [7]: horizontal or downsloping ST depression of at least 1?mm or elevation of 2?mm of at least 1?min duration measured at the J-point plus 60?ms. To quantify individual levels of ischaemia we used the definition “ischaemic load” [3]: ischaemic min/h monitored per patient. The statistic evaluation did not differ from that used in part I. Results. Out of 160 patients, 100 could be examined by Holter monitoring. Because of technical problems we could not record a Holter ECG in 2 of 6 patients with reinfarction. We found one or more perioperative episodes of ST-segment depression in 25 patients (25%). Ischaemic episodes were detected in 15 patients preoperatively, in 12 intraoperatively, and in 10 postoperatively. Three patients had ischaemic episodes during all periods. Patients with pathological ST segments suffered significantly more reinfarctions (3 of 25 vs. 1 of 75 patients) and were older (mean age difference 7 years, P<0.05). Patients with ischaemic episodes and a clinical diagnosis of reinfarction (n=3) demonstrated a dramatic postoperative increase in ischaemic load. Preoperative use of beta-blocking agents did not influence the incidence of ischaemic events. The sensitivity of postoperative Holter ECG monitoring in the diagnosis of reinfarction was 50%, the specificity 92%. Conclusions. Perioperative Holter ECG monitoring is time-consuming, expensive, not very sensitive, and therefore not generally applicable for all patients with prior MI.     

Significance of right bundle branch block in the diagnosis of myocardial ischemia in patients undergoing coronary artery bypass grafting.

BACKGROUND: Perioperative diagnosis of myocardial ischemia following cardiac surgical procedures remains a challenging problem. Particularly, the role of new conduction disturbances as markers of postoperative ischemia is still questionable. The goal of this study was to elucidate the diagnostic significance of new postoperative right bundle branch block (RBBB) for the detection of perioperative myocardial ischemia in patients undergoing elective coronary artery bypass grafting (CABG). METHODS: In 169 consecutive patients, three-channel Holter monitoring and serial assessment of serum enzymes were performed for 48 h, and 12-lead ECG repeated for up to 5 days postoperatively. Postoperative events were classified as either myocardial infarction (MI), transient ischemic events (TIE) or various conduction disturbances. RESULTS: Transient (n=9) or permanent (n=4) RBBB occurred in 13 patients (8%); 14 patients (8%) showed signs of perioperative MI and 18 patients (11%) evidence of TIE. Peak activity of creatine-kinase (CK, 561+/-135 vs. 316+/-19, P<0.05) and CK-MB (22.7+/-3.2 vs. 13.4+/-0.8, P<0.01) were higher in patients with RBBB than in patients without perioperative ischemic events. Peak CK-MB levels were significantly higher in patients with MI as compared to those with RBBB (33.4+/-7.6 vs. 22.7+/-3.2, P<0. 05). Patients with TIE had similar perioperative enzyme levels as patients with no events. CONCLUSION: It is concluded that the combined assessment of repeated 12-lead ECG, continuous Holter monitoring and enzyme analysis allows a reliable diagnosis of perioperative myocardial ischemia and conduction disturbances. The occurrence of new RBBB following elective CABG is indicative of perioperative myocardial necrosis and thus serves as a valuable tool for the diagnosis of new, perioperative ischemic events.     

Early postoperative myocardial morbidity in patients with coronary artery disease undergoing major non-cardiac surgery: correlation with perioperative ischaemia

As a part of a study assessing early postoperative myocardial morbidity in 50 patients with active coronary artery disease undergoing major non-cardiac surgery, the ECG was monitored continuously for 24 hr after the onset of anaesthesia, using a frequency modulated (FM) Holter monitor. Concurrent automated blood pressure and pulse were measured non-invasively at three-minute intervals during anaesthesia and subsequently at five-minute intervals. Thirty patients were monitored with two-site ECG recordings, from modified V1 and V5 (Group A). Twenty patients had seventeen-site ECG monitoring, multiplexing a four by four array of precordial electrodes onto one channel of the frequency modulated recorder (Group B). Tapes were analyzed for noise, supraventricular and ventricular dysrythmias, runs of tachy- and bradycardia, and ST segment changes. These data were correlated with serial standard 12-lead ECGs and CK-MB assay in the 72 hr after surgery. Seven tapes from Group A could not be analyzed. Change (greater than 1 mm) on ST monitoring from both Groups A (14/23), B (14/20), correlated with serial 12-lead ECG and/or CK-MB changes. The majority of first ST change 19/28 (70%) occurred after anaesthesia. In 14/28 (50%) ST change occurred during episodes of tachycardia and elevated blood pressure (greater than 20% above baseline). Nine patients (9/23) in Group A had no ST change; however, six had serial 12-lead ECG and/or CK-MB changes. Six patients (6/20) in Group B had no ST changes, and none of these patients had any change of serial 12-lead ECGs or CK-MB assay. No patient complained of chest pain during the Holter monitoring period. Continual monitoring of heart rate and blood pressure and accurate ST monitoring are essential to detect and treat perioperative myocardial ischemia. A multiple-lead precordial system is substantially more sensitive than traditional two-lead ECG holter monitoring in detecting myocardial ischaemia.     

Normothemic Continuous Blood Cardioplegia Improves Electrophysiologic Recovery after Open Heart Surgery

Background: Myocardial protection during open heart surgery is based on administration of oxygenated blood cardioplegia, the preferred temperature of which is still under debate. The current randomized study was designed to prospectively evaluate the quality of myocardial protection and the functional recovery of the heart with either normothermic (group N) or hypothermic (group H) oxygenated blood cardioplegia.

Methods: Under continuous electrocardiographic Holter monitoring, 42 patients were randomly scheduled to receive either normothermic (33.5 degrees C) or hypothermic (10 degrees C) cardioplegia solutions during coronary bypass grafting surgery. Blood samples for creatinine phosphokinase, creatinine phosphokinase-MB, lactate, epinephrine, and norepinephrine were withdrawn during cardiopulmonary bypass via a coronary sinus cannula.

Results: Active cooling in group H on initiation of cardio-pulmonary bypass was characterized by transition through ventricular fibrillation in 75% of patients, whereas in group N atrial fibrillation occurred in 65% of patients. On myocardial reperfusion, sinus rhythm spontaneously resumed in 95% of group N patients compared to 25% in group H (P = 0.0003). In the latter, 75% of patients developed ventricular fibrillation often followed by complete atrioventricular block, which necessitated temporary pacing for a mean duration of 168+/-32 min. Both groups showed a similar incidence of intraventricular block and ST segment changes. However, the incidence of ventricular premature beats in the first 16 h after cardiopulmonary bypass was significantly greater in group H (P < 0.05), 20 +/-26/h, compared to 3+/-5/h in group N. Blood concentrations of lactate, creatinine phosphokinase, epinephrine, and norepinephrine increased gradually during the operation, but the differences between the groups were not significant.     

Prognostic value of heart rate variability during long-term follow-up in chronic haemodialysis patients with end-stage renal disease.

BACKGROUND: Mortality is high in chronic haemodialysis patients with cardiovascular disease, and many of them die suddenly. Reduced heart rate variability (HRV) is an increased risk for death in various populations, but its prognostic value in haemodialysis patients remains uninvestigated. METHODS: We analysed the associations between 24-h HRV measures and long-term mortality through a prospective follow-up of 31 chronic haemodialysis patients who underwent diagnostic coronary angiography. RESULTS: Of the 31 patients, at baseline, seven had a previous myocardial infarction, five had a history of congestive heart failure and 14 had significant (> or =75%) coronary stenosis (four had multi-vessel stenosis). During follow-up for 60+/-5 months, 14 patients died, 11 of them suddenly. A left ventricular ejection fraction of <0.45, multi-vessel coronary stenosis, ventricular tachycardia on 24-h ECG and decreased/abnormal 24-h HRV (triangular index <22 and abnormal Poincaré plot) carried a univariate risk of all-cause death, while the risk of sudden death was only correlated with decreased HRV (standard deviation of normal-normal R-R interval <50 ms, triangular index <22 and ultra-low frequency power <8.7 ln(ms2)). Multivariate analysis revealed that a triangular index <22 was the best predictor of increased risk for both all-cause and sudden death (hazards ratio (95% CI); 8.1 (1.3-48.6) and 12.6 (1.3-126.4), respectively) and that the association was independent of cardiac function, macrovascular diseases, ventricular arrhythmias and cardiovascular risk factors. The 5-year mortality when the triangular index was > or =22 or <22 was 33 or 88% for patients with coronary artery disease and 0 or 50% for those without. CONCLUSIONS: These results indicate that HRV has an independent prognostic value in chronic haemodialysis patients and identifies an increased risk for all-cause and sudden death.     

The effect of clonidine premedication on hemodynamic responses to microlaryngoscopy and rigid bronchoscopy

The usual hemodynamic response to laryngoscopy and bronchoscopy is an increase in heart rate and arterial blood pressure. Previous work has reported that 10%-18% of the patients develop ischemic ST segment changes during the procedure. Therefore, we performed a prospective, randomized, double-blinded study in 36 patients scheduled for elective microlaryngeal and bronchoscopic surgical procedures to evaluate the effects of 300-microg oral clonidine premedication (n = 18) or placebo (n = 18) on the hemodynamic alterations and the incidence of perioperative myocardial ischemic episodes. Myocardial ischemia was assessed by using continuous electrocardiographic monitoring, beginning 30 min before, and lasting until 24 h after the operation. During the procedure, patients receiving placebo exhibited a significant increase (mean +/- SD) in arterial blood pressure (the systolic increasing from 137+/-11 to 166+/-17 mm Hg, the diastolic increasing from 80+/-11 to 97+/-14 mm Hg) and heart rate (increasing from 79+/-15 to 97+/-12 bpm) compared with the baseline and with the clonidine group. A dose of 300-microg clonidine blunted the hemodynamic response to endoscopy. Ventricular arrhythmias were more frequent in patients who were not premedicated with clonidine. Two patients in the control group, but none in the clonidine group, had evidence of myocardial ischemia. These data should encourage routine premedication with clonidine in patients undergoing microlaryngoscopic and bronchoscopic procedures.     

Small, Oral Dose of Clonidine Reduces the Incidence of Intraoperative Myocardial Ischemia in Patients Having Vascular Surgery

Background: Most new perioperative myocardial ischemic episodes occur in the absence of hypertension or tachycardia. The ability of alpha2 -adrenoceptor agonists to inhibit central sympathetic outflow may benefit patients with coronary artery disease by increasing the myocardial oxygen supply-and-demand ratio.

Methods: A randomized double-blind study design was used in 297 patients scheduled to have elective vascular surgical procedures to evaluate the effects of 2 micro gram/kg sup -1 oral clonidine (n = 145) or placebo (n = 152) on the incidence of perioperative myocardial ischemic episodes, myocardial infarction, and cardiac death. Continuous real-time S-T segment trend analysis (lead II and V5) was performed during anesthesia and surgery and correlated with arterial blood pressure and heart rate before and during ischemic events. Dose requirements for vasoactive and antiischemic drugs to control blood pressure and heart rate as well as episodes of myocardial ischemia (i.e., catecholamines, beta-adrenoceptor antagonists, nitrates, and systemic vasodilators) and fluid volume load were recorded.

Results: Administration of clonidine reduced the incidence of perioperative myocardial ischemic episodes from 39% (59 of 152) to 24% (35 of 145) (P < 0.01). Hemodynamic patterns, percentage of ischemic time, and the number of ischemic episodes per patient did not differ. Nonfatal myocardial infarction developed after operation in four patients receiving placebo compared with none receiving clonidine (day 2 to 21; P = 0.07). The incidence of fatal cardiac events (1 vs. 2) was not different. Dose requirements for vasoactive and antiischemic drugs did not differ between the groups, but the amount of presurgical fluid volume was slightly greater in patients receiving clonidine (951 +/- 388 vs. 867 +/- 381 ml; P < 0.03).