Biomedical subjects

E D Bennett

Publications and source records attributed to E D Bennett.

At least 37 records · Page 2Linked to original sources

PubMed1996

Changes in cardiac output during air ambulance repatriation.

OBJECTIVES: To measure, with the use of suprasternal Doppler ultrasound, the hemodynamic changes in patients and volunteers during air ambulance repatriation. DESIGN: Unblinded prospective observational study. SETTING: Chartered air ambulances for the international repatriation of patients. PATIENTS AND PARTICIPANTS: Six medical crew members and seven patients transported back to hospitals in the UK. INTERVENTIONS: The measurement of non-invasive blood pressure, ECG, heart rate, oxygen saturation and hemodynamic variables with suprasternal Doppler. MEASUREMENTS AND RESULTS: There was a drop in systolic and mean arterial blood pressure in the patient's group once in the air. Oxygen saturation dropped in both groups once at cruising altitude. Heart rate remained unchanged. Stroke distance and minute distance increased significantly in the patient's group and non-significantly in the volunteers. Peak velocity increased significantly in the patient's group. There was an overall reduction of systemic vascular resistance during take off and once at cruising altitude. CONCLUSIONS: Hemodynamic changes happen during air ambulance transportation in fit and healthy volunteers and patients alike. These may be due to a combination of hypobaric hypoxia and gravitational forces. It is necessary to establish if these changes have short- or long-term effects in the critically ill.

Adult↗

PubMed1996

Plasma proinflammatory cytokine concentrations, Acute Physiology and Chronic Health Evaluation (APACHE) III scores and survival in patients in an intensive care unit.

OBJECTIVE: To more clearly define the relationships between plasma proinflammatory cytokine concentrations, physiologic disturbance, and survival in severely ill patients. DESIGN: Prospective, longitudinal, cohort analytic study. SETTING: Teaching hospital intensive care unit (ICU). PATIENTS: Two hundred fifty-one consecutive nonselected patients admitted to the ICU. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Daily Acute Physiology and Chronic Health Evaluation (APACHE) III scores were calculated from clinical and laboratory data. In concurrent blood samples, plasma concentrations were measured of four proinflammatory cytokines (tumor necrosis factor-[TNF] alpha, interleukin [IL]-1 beta, IL-6, and IL-8), all of which are believed to be of central importance in host proinflammatory and immune responses. Plasma TNF concentrations were increased in 42 patients, plasma IL-1 beta in 15 patients, IL-6 in 194 patients, and IL-8 in 52 patients at presentation. Although admission plasma IL-1 beta, IL-6, and IL-8 concentrations were higher in patients who died in the ICU compared with survivors (n = 33; p < .02, p < .01, p < .02, respectively), only admission plasma IL-8 concentrations were higher in patients with a fatal outcome if all in-hospital deaths were considered (n = 53; p = .05). APACHE III score was the best predictor of mortality (odds ratio 11.41; p = .003). Detection, but not the absolute level, of TNF bioactivity in plasma was a weak independent predictor of death (odds ratio 3.17; p = .02). There was no relationship between bacteremia or presence of the systemic inflammatory response syndrome and plasma cytokine concentrations. Nineteen patients were in the ICU for > or = 10 days, and of these 19 patients, 16 patients had prolonged increases of plasma cytokines. Two patients with persistently increased plasma TNF concentrations died. Otherwise, persistently increased plasma cytokine concentrations had a variable relation to daily APACHE scores and to mortality. CONCLUSIONS: Plasma cytokine concentrations fluctuate in serious illness and have a poor correlation with derangement of whole body physiology in seriously ill patients. Only the presence of bioactive TNF in plasma was an independent predictor of mortality. Daily measurement of plasma proinflammatory cytokine concentrations is unlikely to have clinical application in the ICU setting, except possibly in specific subgroups of patients.

APACHE↗

PubMed1996

Enhancement of perioperative tissue perfusion as a therapeutic strategy for major surgery.

Multiple organ dysfunction syndrome (MODS) accounts for most surgical deaths which occur some days postoperatively. Current hypotheses concerning the pathophysiology of MODS place tissue hypoxia and reperfusion as a central feature of the initiation and continuation of the syndrome. Surgical patients are at risk of developing overt and covert tissue hypoxia and hypoperfusion due to anesthetic, surgical, and other factors; and it is known that surgical patients with poor cardiovascular reserve have a worse outcome postoperatively. A number of clinical studies have attempted to intervene early in surgical patients to prophylactically improve tissue perfusion in the perioperative period by augmentation of cardiac output. These studies demonstrate a reduction in mortality and morbidity in these groups of patients. A similar approach has been tried in other groups of critically ill patients, at a later state in the evolution of their illness; these studies have not shown any improvement in outcome. In surgical patients, data show that those with more coexisting pathology and worse cardiac function may benefit most from a treatment approach aimed at improving tissue perfusion; furthermore, this may result in cost savings. The implications for the management of the higher risk surgical patient are obvious. It may no longer be acceptable to undertake surgery in these patients without facilities to monitor and improve cardiac output and tissue perfusion.

Blood Circulation↗

PubMed1995

External high frequency oscillation in normal subjects and in patients with acute respiratory failure.

External high frequency oscillation was performed on 20 healthy volunteers using a cuirass-based system, the Hayek Oscillator. Five-min periods of oscillation were carried out on each subject at frequencies of 1, 2, 3, 4 and 5 Hz. Effective ventilation was measured in terms of the fall in alveolar partial pressure of carbon dioxide immediately after oscillation. The optimum frequency for oscillation was 1-3 Hz but most of the subjects were adequately ventilated over a wide range of frequencies. Thus, the Hayek Oscillator is capable of adequately ventilating normal subjects by means of chest wall oscillation. We also compared external high frequency oscillation with intermittent positive pressure ventilation in five patients with respiratory failure. Using the same inspired oxygen fraction, the external high frequency oscillation replaced intermittent positive pressure ventilation for a 30-min period. External high frequency oscillation improved oxygenation by 16% and reduced the arterial carbon dioxide by 6%. These preliminary findings suggest that normal subjects and intensive care unit patients can be adequately ventilated by means of external high frequency oscillation.

Acute Disease↗

PubMed1995

A comparison of the efficacy of dopexamine and dobutamine for increasing oxygen delivery in high-risk surgical patients.

Peri-operative increase of oxygen delivery has been shown to reduce mortality in high-risk surgical patients. This study compares the effectiveness of dopexamine and dobutamine when used to increase cardiac output as part of a regimen to increase oxygen delivery. Sixteen surgical patients were randomly allocated to receive either dopexamine or dobutamine, which was increased to a stable dose defined as either oxygen delivery index > 600 ml/min/m2, or tachycardia > 20% above baseline, other dysrhythmias or angina. At this "stable" dose there were significant increases in cardiac index (2.4 +/- 0.2 vs 3.7 +/- 0.3 l/min/m2) and oxygen delivery (380 +/- 73 vs 579 +/- 40 ml/min/m2) in the dopexamine group (P < 0.05); but not the dobutamine group. Five out of eight patients receiving dopexamine and three out of eight receiving dobutamine reached target oxygen delivery. Three dobutamine patients, but no dopexamine patients, had angina or dysrhythmias. In preoperative high-risk surgical patients, dopexamine can allow greater increases in oxygen delivery than dobutamine, due to cardiac effects that limit the dobutamine infusion rate.

Adrenergic beta-Agonists↗

PubMed1994

Effects of insertion depth and use of the sidearm of the introducer sheath of pulmonary artery catheters in cardiac output measurement.

OBJECTIVE: To investigate the effects of various insertion depths and sidearm functions of the introducer sheath of pulmonary artery flotation catheters on cardiac output measurement. DESIGN: Prospective, randomized, crossover study. SETTING: A general intensive care unit. PATIENTS: Ten patients who had a pulmonary artery flotation catheter placed in the right internal jugular vein as part of their clinical management. INTERVENTIONS: Cardiac output was measured at three insertion depths of the pulmonary artery catheter, each with a different rate of flow into the introducer sheath. MEASUREMENTS AND MAIN RESULTS: Significant differences of up to 23% occurred in the measurement of cardiac output under the various conditions. Cardiac output measurement is greater, the closer the injection port lies to the introducer sheath and the more open the introducer sheath sidearm. CONCLUSIONS: All users of pulmonary artery catheters should be alert to this problem. For reliable measurements of cardiac output by thermodilution, the cold saline injection port of the pulmonary artery catheter must be downstream of the introducer sheath, and the introducer sidearm must be closed.

Adult↗

PubMed1994

The cardiovascular changes associated with equipotent anaesthesia with either propofol or isoflurane. Particular emphasis on right ventricular function.

The differences in effects of anaesthetic agents on right ventricular function have not been studied. We have developed a cross-over study design to compare the effects of propofol and isoflurane on cardiac and specifically right ventricular function. Ten patients were anaesthetised with equivalent MAC of isoflurane to MIR of propofol. After measurements had been taken on the randomly assigned first agent the patients were crossed over to the other agent and measurements were repeated. Cardiac function was assessed using a pulmonary artery catheter with a fast response thermistor. There were no differences in heart rate or blood pressure between the two agents suggesting that equivalent anaesthetic doses had been given. There were significantly (P < 0.05) higher cardiac output (4.0 to 4.5 l.min-1), right ventricular ejection fraction (35.1 to 39.4%), stroke volume (35.4 to 39.6 ml) and right ventricular end-diastolic volume index (102 to 110 ml.m2-1) with propofol compared to isoflurane. We conclude that propofol results in improved right ventricular performance compared to isoflurane. We have also shown that anaesthetic agents can be compared using a cross-over study design, and have demonstrated that MAC of isoflurane and MIR of propofol can be directly compared. We suggest that propofol may be a more suitable agent than isoflurane for anaesthesia in patients who may already have impaired right ventricular function and in whom maintaining high cardiac output may be beneficial.

Aged↗

PubMed1993

A randomized clinical trial of the effect of deliberate perioperative increase of oxygen delivery on mortality in high-risk surgical patients.

OBJECTIVE: To assess the effect of deliberate perioperative increase in oxygen delivery on mortality and morbidity in patients who are at high risk of both following surgery. DESIGN: Prospective, randomized clinical trial. SETTING: A teaching hospital general intensive care unit, London, England. PATIENTS: A total of 107 surgical patients, who were assessed as high risk from previously identified criteria, were studied during an 18-month period. INTERVENTIONS: Patients were randomly assigned to a control group (n = 54) that received best standard perioperative care, or to a protocol group (n = 53) that, in addition, had deliberate increase of oxygen delivery index to greater than 600 mL/min per square meter by use of dopexamine hydrochloride infusion. OUTCOME MEASURES: Mortality and complications were assessed to 28 days postoperatively. RESULTS: Groups were similar with respect to demographics, admission criteria, operation type, and admission hemodynamic variables. Groups were treated similarly to maintain blood pressure, arterial saturation, hemoglobin concentration, and pulmonary artery occlusion pressure; however, once additional treatment with dopexamine hydrochloride had been given, the protocol group had significantly higher oxygen delivery preoperatively (median, 597 vs 399 mL/min per square meter; P < .001) and postoperatively (P < .001). Results indicate a 75% reduction in mortality (5.7% vs 22.2%; P = .015) and a halving of the mean (+/- SEM) number of complications per patient (0.68 [+/- 0.16] vs 1.35 [+/- 0.20]; P = .008) in patients randomized to the protocol group. CONCLUSION: Perioperative increase of oxygen delivery with dopexamine hydrochloride significantly reduces mortality and morbidity in high-risk surgical patients.

Aged↗

PubMed1993

Comparison of clinical information gained from routine blood-gas analysis and from gastric tonometry for intramural pH.

The measurement of gastric intramucosal pH (pHi) has been advocated to assist in decision-making for critically ill patients. To assess whether the information obtained from the measurement of pHi can be obtained from other measurements of metabolic acidosis, we studied 20 consecutive patients admitted to the intensive care unit. A mean of eight (range two to fourteen) data sets per patient were obtained, comprising measurement of arterial pH, pO2, pCO2, and oxygen saturation, tonometer balloon fluid pCO2, arterial pressures, and cardiac output. Bicarbonate concentration, base deficit or excess in blood and extracellular fluid, and pHi were calculated from these measurements. Relations between the variables and pHi were assessed by within-subject correlation comparisons. There were significant correlations (r > 0.6, p < 0.001) between markers of metabolic acidosis (base deficit in blood and extracellular fluid and bicarbonate concentration) and pHi. A blood base deficit of -4.65 or less and an extracellular-fluid base deficit of -6.13 or less could estimate pHi below 7.32 (lower limit of normal range) with sensitivity of at least 77% and specificity of at least 96%. There was no patient in whom either pHi or blood base deficit consistently reflected acidosis when the other variable did not. We conclude that the information that is obtained by gastric tonometry for pHi can be obtained more simply from measurements of metabolic acidosis; these variables can be calculated from routinely available blood-gas measurements.

Acidosis↗

PubMed1993

Propofol or midazolam for short-term alterations in sedation.

It is often necessary to adjust a patient's sedation level while they are in the intensive care unit. The purpose of this study was to compare propofol with midazolam for controlling short-term alterations in sedation. Twenty-three patients undergoing an interactive procedure, physiotherapy, during mechanical ventilation of the lungs were studied. The patients were randomly assigned to receive infusions of propofol or midazolam for sedation. Sedation was assessed using the method of Ramsay, where 3 is drowsy responding only to commands; and 5 is asleep with a slow response to light glabellar tap. Prior to physiotherapy sedation was deepened from 3 to 5 by increasing the sedative infusion rate, and level 5 was maintained during physiotherapy by adjusting the infusion rate whenever necessary. After physiotherapy, the sedative dose was reduced until level 3 was again achieved. During physiotherapy, sedation level 5 was achieved for 53.9% of the time with propofol but for only 25.7% with midazolam (P < 0.01). After physiotherapy, those patients sedated with propofol re-awakened to level 3 faster (8.3 +/- 2.3 min, mean +/- SE) than those receiving midazolam (92.8 +/- 35.0 min, P < 0.05). After physiotherapy, a further 1.8 +/- 0.5 dose adjustments were required to the midazolam infusion while only 0.4 +/- 0.2 adjustments were required to the propofol infusion (P < 0.05). During physiotherapy 3.0 +/- 0.5 dose adjustments to the propofol dose were required compared with 3.6 +/- 0.5 adjustments to the midazolam dose (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1993

Early results of intravascular oxygenation.

We have used the intravascular oxygenator (IVOX) in eight patients (14-76 years) with acute respiratory failure. At the time of referral for IVOX all patients were on inotropic support, five had pneumothoraces and two were on haemofiltration. Ventilatory data before IVOX were: ventilated for 2-14 days (median 6), PEEP 5-12 cm H2O (12), PIP 34-95 cm H2O (49), FiO2 0.7-1 (1), PaO2 5.4-26 KPa (8.5) and PaCO2 3.7-23 KPa (8). The intravascular oxygenator was used for 6 h-12 days (median 4), the oxygen transfer achieved was 68-140 ml/min (85) and the carbon dioxide removed was 40-106 ml/min (59). It was possible to decrease the ventilator settings with a significant increase in the PaO2 by 48 h (P < 0.05) but the fall in PaCO2 did not reach significance. As the IVOX was turned from "off" to "on" the mean PaO2 increase was 0.35 KPa +/- 0.14 SEM (P = 0.04) and the mean PaCO2 decrease 0.7 KPa +/- 0.2 SEM (P = 0.02) without any significant change in cardiac output. Two patients survived and six died from multisystem failure with three patients being hypoxic at the time of death. Postmortem examinations on five patients did not reveal any IVOX-related complications. We conclude that IVOX is safe but it is not as efficient in gas exchange as extracorporeal membrane oxygenation at present. Further improvement in the gas exchange efficiency of this prototype could render IVOX a very useful device.

Acute Disease↗

PubMed1993

The peri-operative management of surgical insertion and removal of the intravenous oxygenator device (IVOX). A report of nine cases.

Intravenous oxygenation (IVOX) is a new technique for augmentation of gas exchange in patients who require near maximal conventional ventilatory support. Patients who require IVOX are, by definition, critically ill with a high expected mortality. At present, these high risk patients must be transferred to the operating theatre for the IVOX device to be inserted. This report describes the anaesthetic problems associated with nine patients in whom an IVOX device was inserted and removed in our institution. The mortality was six out of nine patients; all deaths occurred with the IVOX device in situ. Three patients died within 6 h of insertion. Four patients were female. The patients' ages ranged from 14 to 76 years. There were few immediate ventilation changes in the first 4 h after IVOX insertion. Inspired oxygenation concentration was reduced in only one patient. Positive end-expiratory pressure was not reduced. Peak inspiratory pressure decreased in four patients. Arterial oxygen tension increased in four patients (range 0.1-2.5 kPa) and decreased in five (range 0.1-3.4 kPa). Arterial carbon dioxide tension increased in one patient (0.3 kPa) and decreased in eight (range 0.1-2.7 kPa). Inotropic support with adrenaline, dobutamine and noradrenaline needed to be initiated or increased in eight patients. Eight patients required 2-4 units of blood to be transfused during IVOX insertion or in the following 2 h. One patient suffered an asystolic cardiac arrest during the operation, but was resuscitated successfully. Three patients survived to have the IVOX removed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1993

The use of dopexamine hydrochloride to increase oxygen delivery perioperatively.

Perioperative increases in oxygen delivery may reduce morbidity and mortality in certain groups of surgical patients. However positive inotropic drugs, such as dobutamine and epinephrine themselves, may increase oxygen demand. Dopexamine hydrochloride is a new dopamine analogue with action at beta 2-adrenoceptors and DA1 receptors, but it possesses no direct alpha-adrenoceptor activity. We assessed the suitability of dopexamine to increase oxygen delivery perioperatively in eight patients having vascular surgery and studied its effects on oxygen demand. Oxygen delivery was increased toward 600 mL.min-1.m-2 by intravenous (IV) fluid infusion and IV titration of dopexamine hydrochloride. Oxygen delivery could be increased preoperatively (375 +/- 43 to 552 +/- 50 mL.min-1.m-2, P < 0.05) with > 600 mL.min-1.m-2 being achieved in five patients. This increase was achieved without significant increase in total body oxygen consumption (114 +/- 10 to 123 +/- 7 mL.min-1.m-2 P > 0.05) or rate pressure product (13.7 +/- 2.8 x 10(3) to 13.5 +/- 2.1 x 10(3) mm Hg.beats/min, P > 0.05). Postoperatively oxygen delivery was increased again without an increase in oxygen consumption (126 +/- 10 mL.min-1.m-2, P > 0.05) or rate pressure product (14.2 +/- 0.9 x 10(3) mm Hg.beats/min, P > 0.05). Dopexamine hydrochloride may provide a method for increasing oxygen delivery perioperatively with only limited increase in total body or myocardial oxygen demand.

Adrenergic Agonists↗

PubMed1992

A narrow range, medium molecular weight pentastarch reduces structural organ damage in a hyperdynamic porcine model of sepsis.

OBJECTIVE: to compare diafiltered 6% pentastarch (Pentafraction--PDP, MWn 120,000 and MWw 280,000) and native pentastarch (Pentaspan--PSP, MWn 63,000 and MWw 264,000 dalton) in a porcine model of faecal peritonitis. DESIGN: Randomised prospective study in 12 adolescent pigs. INTERVENTIONS: Prior to infection the study solution was infused to increase Qt by 25%. Thereafter adjustments in infusion rate were made (up to 1 l/h) in an attempt to maintain Qt at 25% above baseline values. MEASUREMENTS AND RESULTS: Animals were sacrificed at 8 h. Tissue was excised from the right lobe of liver and from the right lung and fixed for later electron microscopy and digital morphometric analysis. Patent sinusoidal lumen was significantly greater in group PDP compared to PSP (11.3% +/- 2.3% of liver tissue versus 4.8% +/- 1.1%, p < 0.05) and this was accounted for by a significantly lower proportion of sinusoidal lumen occluded with white cells (2.1% +/- 0.6% versus 6.6% +/- 1.9%, p < 0.05). Similarly, patent capillary represented a significantly higher proportion of lung tissue for group PDP versus PSP (26.2% +/- 1.9% versus 18.5% +/- 2.7%, p < 0.05). The arithmetic mean alveolar capillary barrier thickness was significantly greater in group PSP than in group PDP (4.3 +/- 0.3 microns versus 2.5 +/- 0.3 microns, p < 0.01). CONCLUSIONS: The molecular weight profile of Pentafraction was associated with less structural organ damage including less tissue oedema and less white cell occlusion.

Biopsy↗

PubMed1992

Validation of bedside measurements of absolute human renal blood flow by a continuous thermodilution technique.

BACKGROUND AND METHODS: There is a clinical need for a system that would allow rapid assessment of renal blood flow in patients with oliguric circulatory shock. A local, continuous thermodilution technique for the measurement of renal venous blood flow, using readily available equipment, was developed. To test the hypothesis that this system would allow measurement of renal blood flow in clinical situations, we compared simultaneous measurements made by the continuous thermodilution technique with measurements of: a) absolute flow measured by volumetric collection in an in vitro flow model; b) renal arterial blood flow measured by electromagnetic flow probe under changing hemodynamic conditions in nine pigs; and c) calculated renal blood flow derived from a clearance technique in 16 patients after cardiac catheterization. The technique utilizes a short-duration, constant infusion of room temperature normal saline into the renal vein via a retrograde thermodilution catheter, with measurement of flow at a thermistor 1 cm back from the tip of the catheter. RESULTS: The method measured absolute blood flow in an in vitro model, with a correlation coefficient of .99 over blood flows ranging from 55 to 885 mL/min (r2 = .98). There was a .92 correlation coefficient with renal arterial blood flow measured by electromagnetic flow probe in a pig model (r2 = .85), and a .8 correlation with simultaneous measurement of renal blood flow by corrected iodohippurate clearance in humans (r2 = .64). Compared with electromagnetic flow probe measurements, a single measurement by the thermodilution technique would be accurate to within 80 mL/min in 95% of cases. Variability between individual measurements, expressed as the mean of the coefficient of variance for each patient, was 5.5 +/- 3.7%. CONCLUSIONS: This technique is simple to use, requires only venous cannulation and injection of normal saline, and allows rapidly repeatable, immediately available measurements of renal blood flow in a wide range of clinical circumstances, including severe renal impairment or anuria.

Animals↗

PubMed1992

Isoflurane and propofol for long-term sedation in the intensive care unit. A crossover study.

Propofol and isoflurane have been reported recently to offer better sedation than alternative agents in patients who require long-term ventilation in the Intensive Care Unit. This is the first report of a direct comparison between propofol and isoflurane. Twenty-four patients predicted to require artificial ventilation for at least 48 h were entered into a randomised crossover study to monitor sedation quality and time to recovery from sedation. There were no significant differences between the two agents in either end-point, with over 95% optimal sedation achieved by the use of each drug. Few adverse events were noted. Technological advances in the administration of volatile agents as long-term sedatives in the Intensive Care Unit may facilitate their more widespread use.

Adolescent↗

PubMed1991

The effects of dobutamine, dopexamine and fluid on hepatic histological responses to porcine faecal peritonitis.

We studied the effects of two catecholamines with differing receptor profiles on hepatic blood flow and hepatic structure in a porcine model of faecal peritonitis. We treated animals with dopexamine (group Dp) or dobutamine (group Db) and fluid, or fluid alone as a control, to achieve a 25% increase in Qt from baseline values. After the induction of faecal peritonitis the increased Qt was maintained throughout the 8 h study period by adjustment of the fluid infusion rate. The dose of catecholamines remained constant. Hepatic blood flow was correspondingly maintained at above baseline values throughout the study. Post-mortem liver biopsy specimens were analysed from experimental animals and 5 sham animals who had not been instrumented or infected. In experimental animals there was a reduction in sinusoidal patency between sham and group Dp (76% of total sinusoid vs 51%, p less than 0.05) and group Dp and control (51% vs 33%, p less than 0.05) or groups Dp and Db (51% vs 34%, p less than 0.05) animals. This was accounted for by an increase in sinusoidal leukocytes and endothelial swelling. In addition to the changes noted above there was marked hepatocellular destruction in group Db. We conclude that maintenance of organ blood flow does not guarantee structural integrity in the sepsis syndrome and hepatocellular damage was greater in group Db than group Dp or control.

Adrenergic Agonists↗

PubMed1991

Risk stratification for arrhythmic events in postinfarction patients based on heart rate variability, ambulatory electrocardiographic variables and the signal-averaged electrocardiogram.

The value of heart rate variability, ambulatory electrocardiographic (ECG) variables and the signal-averaged ECG in the prediction of arrhythmic events (sudden death or life-threatening ventricular arrhythmias) was assessed before hospital discharge in 416 consecutive survivors of acute myocardial infarction. During the follow-up period (range 1 to 1,112 days), there were 24 arrhythmic events and 47 deaths. The initial relation between several prognostic factors and arrhythmic events was explored with use of the Kaplan-Meier product limit estimates of survival function. Impaired heart rate variability less than 20 ms (p less than 0.0000), late potentials (p less than 0.0000), ventricular ectopic beat frequency (p less than 0.0000), repetitive ventricular forms (p less than 0.0000), left ventricular ejection fraction less than 40% (p less than 0.02) and Killip class (p less than 0.02) were identified as significant univariate predictors of arrhythmic events. When these variables were analyzed by using a stepwise Cox regression model, only impaired heart rate variability, followed by late potentials and repetitive ventricular forms remained independent predictors of arrhythmic events. The combination of impaired heart rate variability and late potentials had a sensitivity of 58%, a positive predictive accuracy of 33% and a relative risk of 18.5 for arrhythmic events and was superior to other combinations including those incorporating left ventricular function, exercise ECG, ventricular ectopic beat frequency and repetitive ventricular forms. These results suggest that a simple method of assessment based on heart rate variability and the signal-averaged ECG can select a small subgroup of survivors of myocardial infarction at high risk of future life-threatening arrhythmias and sudden death.

Arrhythmias, Cardiac↗