Outcome of cardiac arrests attended by emergency medical services staff at community outpatient dialysis centers.

Cardiac arrest is the leading cause of death among dialysis patients in the United States. We measured the outcome of cardiac arrests attended by Emergency Medical Services (EMS) staff at hemodialysis facilities in a 14-year population-based retrospective study to identify cardiac arrest cases at a dialysis unit. Associated factors were determined using unconditional logistic regression. Of the 102 cardiac arrests identified around the time of dialysis, 10 occurred before, 72 during, and 20 after hemodialysis. The initial measured abnormality was ventricular fibrillation or tachycardia in 72 cases. Of those who survived transportation to a hospital, survival to discharge was 24 with 15% survival at 1 year. Compared to arrests that occurred prior to dialysis, the odds of ventricular fibrillation were 5-fold greater in patients on dialysis but 14-fold greater in those arresting after dialysis. One-third of cases occurred after the introduction of automated external defibrillators, and in half of the cases these devices were attached prior to EMS arrival. Once these devices were attached, most were used for defibrillation. We conclude that ventricular arrhythmias are the predominant features among arrested in-center dialysis patients with most occurrences during dialysis. The role of these devices in dialysis units will need a larger study to evaluate their efficacy.

Apolipoprotein E genotypes and outcome from out of hospital cardiac arrest.

Genetic factors may influence outcome from cardiac arrest. In Seattle, WA, paramedics collected blood specimens from patients who had suffered cardiac arrest outside of a medical institution (out of hospital cardiac arrest). We examined associations between apolipoprotein E (APOE) genotype and outcome in 134 who died "in the field", 131 who died in the hospital, 198 patients who were discharged from hospital alive, and 64 control subjects. APOE genotype was not significantly related to outcome, including being alive at and being independent by 3 months after the arrest. Specifically, having one or two alleles of APOE epsilon4 or having APOE epsilon3/epsilon3 was not related to outcome, even after controlling for age, sex, race, and initial rhythm. We failed to confirm previous studies and found no significant associations between APOE genotype and outcome from out of hospital cardiac arrest.

Randomized clinical trial of magnesium, diazepam, or both after out-of-hospital cardiac arrest.

OBJECTIVE: To evaluate the feasibility, safety, and efficacy of interventions aimed at improving neurologic outcome after cardiac arrest. METHODS: The authors conducted a double-blind, placebo-controlled, randomized clinical trial with factorial design to see if magnesium, diazepam, or both, when given immediately following resuscitation from out-of-hospital cardiac arrest, would increase the proportion of patients awakening, defined as following commands or having comprehensible speech. If the patient regained a systolic blood pressure of at least 90 mm Hg and had not awakened, paramedics injected IV two syringes stored in a sealed kit. The first always contained either 2 g magnesium sulfate (M) or placebo (P); the second contained either 10 mg diazepam (D) or P. Awakening at any time by 3 months was determined by record review, and independence at 3 months was determined by telephone calls. Over 30 months, 300 patients were randomized in balanced blocks of 4, 75 each to MD, MP, PD, or PP. The study was conducted under waiver of consent. RESULTS: Despite the design, the four treatment groups differed on baseline variables collected before randomization. Percent awake by 3 months for each group were: MD, 29.3%; MP, 46.7%; PD, 30.7%; PP, 37.3%. Percent independent at 3 months were: MD, 17.3%; MP, 34.7%; PD, 17.3%; PP, 25.3%. Significant interactions were lacking. After adjusting for baseline imbalances, none of these differences was significant, and no adverse effects were identified. CONCLUSIONS: Neither magnesium nor diazepam significantly improved neurologic outcome from cardiac arrest.

Out-of-hospital cardiac arrest in men and women.

BACKGROUND: The incidence of sudden cardiac death is roughly 3 times greater in men than in women. However, in patients treated for out-of-hospital cardiac arrest, the relationships between sex and survival after adjustment for age and cardiac rhythm are unclear. METHODS AND RESULTS: In this retrospective cohort study, we examined 7069 men and 2582 women who were treated for out-of-hospital cardiac arrest in Seattle and suburban King County between 1990 and 1998. We compared successful prehospital resuscitation (hospital admission) and survival from event to discharge in men and women. Women had markedly reduced rates of ventricular fibrillation (VF), slightly older age, fewer witnessed arrests, and fewer arrests in public locations than men. Although their unadjusted resuscitation rate was lower (29% versus 32%, P<0.0001), women had a greater likelihood of resuscitation than men after adjustment for VF (odds ratio [OR] 1.13; 95% confidence interval [CI], 1.03 to 1.25) and after adjustment for VF plus additional factors (OR, 1.27; 95% CI, 1.14 to 1.41). The difference in resuscitation rates between men and women decreased as they aged (test for trend, P<0.0001). Unadjusted survival rates were also lower in women than in men (11% versus 15%, P<0.0001). Women had similar survival after adjustment for VF (OR, 0.97; 95% CI, 0.85 to 1.11) and after adjustment for VF plus additional factors (OR, 1.09; 95% CI, 0.93 to 1.27). CONCLUSIONS: The lower unadjusted resuscitation and survival rates observed in women were primarily due to women's lower incidence of VF, a relatively favorable cardiac rhythm. After adjustment for VF and other factors, women had higher resuscitation rates than men, but similar rates of survival from event to discharge.

Action sequence for layperson cardiopulmonary resuscitation.

Although some minor modifications were forged, the general consensus was to maintain most of the current guidelines for phone first/phone fast, no-assisted-ventilation CPR, the A-B-C (vs C-A-B) sequence of CPR, and the recovery position. The decisions to leave these guidelines as they are were based on a lack of evidence to justify the proposed changes, coupled with a reluctance to make revisions that would require major changes in worldwide educational practices without such evidence.Nonetheless, some major changes were made. The time-honored procedure ol pulse check by lay rescuers was eliminated altogether and replaced with an assessment for other signs of circulation. Likewise, it was recommended that even the professional rescuer now check for these other signs of circulation. Although professional rescuers may simultaneously check for a pulse, they should do so only for a short period of time (within 10 seconds). There was also enthusiasm for deleting the ventilation aspect of EMS dispatcher-assisted CPR instructions that are provided to rescuers at the scene who are inexperienced in CPR. lt was made clear, though, that the data are applicable only to adult patients who are receiving CPR and that the data are appropriate most for EMS systems with rapid response times.

Influenza vaccination and the risk of primary cardiac arrest.

Influenza epidemics are associated with an excess of mortality not only from respiratory diseases but also from other causes, and cardiovascular mortality increases abruptly during influenza epidemics, with little evidence of a lag period. In a population-based case-control study, the authors examined whether influenza vaccination was associated with a reduced risk of out-of-hospital primary cardiac arrest (PCA), a major contributor to cardiovascular mortality in the community. Cases of PCA (n = 342) without prior heart disease or life-threatening comorbidity that occurred in King County, Washington, were identified from paramedic incident reports from October 1988 to July 1994. Demographically similar controls (n = 549) were identified from the community by using random digit dialing. Spouses of subjects were interviewed to assess treatment with influenza vaccine during the previous year and other risk factors. After adjustment for demographic, clinical, and behavioral risk factors, influenza vaccination was associated with a reduced risk of PCA (odds ratio = 0.51, 95 percent confidence interval: 0.33, 0.79). The authors suggest that while the association of influenza vaccination with a reduced risk of PCA is consistent with cohort studies of influenza vaccination and total mortality, further studies are needed to determine whether the observed association reflects protection or selection.

Advantages and disadvantages of trial designs: a review of analysis methods for ICD studies. AVID Investigators.

General modalities of analyses that have been used for ICD studies are reviewed. Published "typical" examples are briefly described. The historical cohort method is exemplified with previously unpublished data from the Seattle Cardiac Arrest Survivor database. The AVID Study database is used to compare the results obtained from nonrandomized methodologies with randomized methodologies. Particular issues related to the use of the ICD for example, mode of death, inability to blind, selection practice, and treatment decision times make this a natural pedagogic platform.

Dietary intake of long-chain n-3 polyunsaturated fatty acids and the risk of primary cardiac arrest.

Whether the dietary intake of long-chain n-3 polyunsaturated fatty acids (PUFAs) from seafood reduces the risk of ischemic heart disease remains a source of controversy, in part because studies have yielded inconsistent findings. Results from experimental studies in animals suggest that recent dietary intake of long-chain n-3 PUFAs, compared with saturated and monounsaturated fats, reduces vulnerability to ventricular fibrillation, a life-threatening cardiac arrhythmia that is a major cause of ischemic heart disease mortality. Until recently, whether a similar effect of long-chain n-3 PUFAs from seafood occurred in humans was unknown. We summarize the findings from a population-based case-control study that showed that the dietary intake of long-chain n-3 PUFAs from seafood, measured both directly with a questionnaire and indirectly with a biomarker, is associated with a reduced risk of primary cardiac arrest in humans. The findings also suggest that 1) compared with no seafood intake, modest dietary intake of long-chain n-3 PUFAs from seafood (equivalent to 1 fatty fish meal/wk) is associated with a reduction in the risk of primary cardiac arrest; 2) compared with modest intake, higher intakes of these fatty acids are not associated with a further reduction in such risk; and 3) the reduced risk of primary cardiac arrest may be mediated, at least in part, by the effect of dietary n-3 PUFA intake on cell membrane fatty acid composition. These findings also may help to explain the apparent inconsistencies in earlier studies of long-chain n-3 PUFA intake and ischemic heart disease.

Amiodarone for resuscitation after out-of-hospital cardiac arrest due to ventricular fibrillation.

BACKGROUND: Whether antiarrhythmic drugs improve the rate of successful resuscitation after out-of-hospital cardiac arrest has not been determined in randomized clinical trials. METHODS: We conducted a randomized, double-blind, placebo-controlled study of intravenous amiodarone in patients with out-of-hospital cardiac arrest. Patients who had cardiac arrest with ventricular fibrillation (or pulseless ventricular tachycardia) and who had not been resuscitated after receiving three or more precordial shocks were randomly assigned to receive 300 mg of intravenous amiodarone (246 patients) or placebo (258 patients). RESULTS: The treatment groups had similar clinical profiles. There was no significant difference between the amiodarone and placebo groups in the duration of the resuscitation attempt (42+/-16.4 and 43+/-16.3 minutes, respectively), the number of shocks delivered (4+/-3 and 6+/-5), or the proportion of patients who required additional antiarrhythmic drugs after the administration of the study drug (66 percent and 73 percent). More patients in the amiodarone group than in the placebo group had hypotension (59 percent vs. 48 percent, P=0.04) or bradycardia (41 percent vs. 25 percent, P=0.004) after receiving the study drug. Recipients of amiodarone were more likely to survive to be admitted to the hospital (44 percent, vs. 34 percent of the placebo group; P=0.03). The benefit of amiodarone was consistent among all subgroups and at all times of drug administration. The adjusted odds ratio for survival to admission to the hospital in the amiodarone group as compared with the placebo group was 1.6 (95 percent confidence interval, 1.1 to 2.4; P=0.02). The trial did not have sufficient statistical power to detect differences in survival to hospital discharge, which differed only slightly between the two groups. CONCLUSIONS: In patients with out-of-hospital cardiac arrest due to refractory ventricular arrhythmias, treatment with amiodarone resulted in a higher rate of survival to hospital admission. Whether this benefit extends to survival to discharge from the hospital merits further investigation.

Influence of cardiopulmonary resuscitation prior to defibrillation in patients with out-of-hospital ventricular fibrillation.

CONTEXT: Use of automated external defibrillators (AEDs) by first arriving emergency medical technicians (EMTs) is advocated to improve the outcome for out-of-hospital ventricular fibrillation (VF). However, adding AEDs to the emergency medical system in Seattle, Wash, did not improve survival. Studies in animals have shown improved outcomes when cardiopulmonary resuscitation (CPR) was administered prior to an initial shock for VF of several minutes' duration. OBJECTIVE: To evaluate the effects of providing 90 seconds of CPR to persons with out-of-hospital VF prior to delivery of a shock by first-arriving EMTs. DESIGN: Observational, prospectively defined, population-based study with 42 months of preintervention analysis (July 1, 1990-December 31, 1993) and 36 months of post-intervention analysis (January 1, 1994-December 31, 1996). SETTING: Seattle fire department-based, 2-tiered emergency medical system. PARTICIPANTS: A total of 639 patients treated for out-of-hospital VF before the intervention and 478 after the intervention. INTERVENTION: Modification of the protocol for use of AEDs, emphasizing approximately 90 seconds of CPR prior to delivery of a shock. MAIN OUTCOME MEASURES: Survival and neurologic status at hospital discharge determined by retrospective chart review as a function of early (<4 minutes) and later (> or =4 minutes) response intervals. RESULTS: Survival improved from 24% (155/639) to 30% (142/478) (P=.04). That benefit was predominantly in patients for whom the initial response interval was 4 minutes or longer (survival, 17% [56/321] before vs 27% [60/220] after; P = .01). In a multivariate logistic model, adjusting for differences in patient and resuscitation factors between the periods, the protocol intervention was estimated to improve survival significantly (odds ratio, 1.42; 95% confidence interval, 1.07-1.90; P = .02). Overall, the proportion of victims who survived with favorable neurologic recovery increased from 17% (106/634) to 23% (109/474) (P = .01). Among survivors, the proportion having favorable neurologic function at hospital discharge increased from 71% (106/150) to 79% (109/138) (P<.11). CONCLUSION: The routine provision of approximately 90 seconds of CPR prior to use of AED was associated with increased survival when response intervals were 4 minutes or longer.

Weekly and seasonal variation in the incidence of cardiac arrests.

BACKGROUND: Patterns of temporal variation of cardiac arrests may be important for understanding mechanisms leading to the onset of acute cardiovascular disorders. Previous studies have reported diurnal variation of the onset of cardiac arrests, with high incidence in the morning and in the evening, lack of daily variation during the week, and some seasonal variation. METHODS AND RESULTS: We explored weekly and yearly (seasonal) temporal variation in 6603 out-of-hospital cardiac arrests attended by the Seattle Fire Department. We observed daily variation that peaks on Monday and seasonal variation that peaks in the winter. CONCLUSIONS: Cardiac arrests do not occur randomly during the week or year but follow certain periodic patterns. These patterns are probably associated with patterns of activities.

Human immunodeficiency virus seroprevalence among adults treated for out-of-hospital cardiac arrest in Seattle, Washington, 1989-1993.

STUDY OBJECTIVE: To estimate the potential risk of HIV exposure for those providing emergency care for out-of-hospital cardiac arrest in Seattle, Washington, by surveying the seroprevalence of HIV in the patient population. METHODS: We surveyed the seroprevalence of HIV among 1,474 persons treated for out-of-hospital cardiac arrest by paramedics during the years 1989 through 1993. Blood specimens were obtained at the site of cardiac arrest, stripped of personal identifiers, and tested for HIV-1 and HIV-2 by enzyme immunoassay and Western blot. RESULTS: Among the 1,011 men, 8 (.8%, 95 percent confidence interval .3% to 1.4%) were seropositive for HIV-1 during this 5-year period; all 8 were younger than age 55. No serologic evidence of HIV infection was detected among the 463 women. CONCLUSION: The seroprevalence of HIV in this population was relatively low. Risk of possible HIV transmission during paramedic treatment was remote.

Utility of the prehospital electrocardiogram in diagnosing acute coronary syndromes: the Myocardial Infarction Triage and Intervention (MITI) Project.

OBJECTIVES: We sought to determine whether the prehospital electrocardiogram (ECG) improves the diagnosis of an acute coronary syndrome. BACKGROUND: The ECG is the most widely used screening test for evaluating patients with chest pain. METHODS: Prehospital and in-hospital ECGs were obtained in 3,027 consecutive patients with symptoms of suspected acute myocardial infarction, 362 of whom were randomized to prehospital versus hospital thrombolysis and 2,665 of whom did not participate in the randomized trial. Prehospital and hospital records were abstracted for clinical characteristics and diagnostic outcome. RESULTS: ST segment and T and Q wave abnormalities suggestive of myocardial ischemia or infarction were more common on both the prehospital and hospital ECGs of patients with as compared with those without acute coronary syndromes (p < or = 0.00001). Those with prehospital thrombolysis were more likely to show resolution of ST segment elevation by the time of hospital admission (14% vs. 5% in patients treated in the hospital, p = 0.004). In patients not considered for prehospital thrombolysis, both persistent and transient ST segment and T or Q wave abnormalities discriminated those with from those without acute coronary ischemia or infarction. Compared with ST segment elevation on a single ECG, added consideration of dynamic changes in ST segment elevation between serial ECGs improved the sensitivity for an acute coronary syndrome from 34% to 46% and reduced specificity from 96% to 93% (both p < 0.00004). Overall, compared with abnormalities observed on a single ECG, consideration of serial evolution in ST segment, T or Q wave or left bundle branch block (LBBB) abnormalities between the prehospital and initial hospital ECG improved the diagnostic sensitivity for an acute coronary syndrome from 80% to 87%, with a fall in specificity from 60% to 50% (both p < 0.000006). CONCLUSIONS: ECG abnormalities are an early manifestation of acute coronary syndromes and can be identified by the prehospital ECG. Compared with a single ECG, the additional effect of evolving ST segment, T or Q waves or LBBB between serially obtained prehospital and hospital ECGs enhanced the diagnosis of acute coronary syndromes, but with a fall in specificity.

Circadian variations in the occurrence of cardiac arrests: initial and repeat episodes.

BACKGROUND: Patterns of temporal variation of cardiac arrests may be important for understanding mechanisms leading to the onset of acute cardiovascular disorders. Previous studies reported diurnal variation of the onset of cardiac arrests, with high incidence in the morning and in the evening, lack of daily variation during the week, and some seasonal variation. The association between the time of day and recurrent cardiac arrests has not been previously examined. METHODS AND RESULTS: We explored temporal variation in 6603 out-of-hospital cardiac arrests attended by the Seattle Fire Department. The data exhibit diurnal variation, with a low incidence at night and two peaks of approximately the same size (at 8 to 11 AM and 4 to 7 PM). The evening peak is attributed primarily to the patients found in ventricular fibrillation, whereas arrests that show other rhythms exhibit mainly a morning peak. Cardiac arrests associated with survival have more pronounced diurnal variation than episodes in which survival did not occur. This difference persists after adjustment for rhythm. For 597 patients who had at least two separate cardiac arrests, we found no overall association between the times of day of the recurrent arrests. For women, however, the times of day of the first and second arrests were closer to each other than one would expect if the times were entirely unrelated. CONCLUSIONS: Cardiac arrests do not occur randomly during the day, but rather follow certain periodic patterns. These patterns are probably associated with patterns of daily activities. The hypothesis that cardiac arrests are triggered by a person's activity rather than by some underlying characteristics of his or her disease is supported by the lack of association between the times of the first and second arrests in the patients with recurrent arrests.

Family history as a risk factor for primary cardiac arrest.

BACKGROUND: The hypothesis that a family history of myocardial infarction (MI) or primary cardiac arrest (PCA) is an independent risk factor for primary cardiac arrest was examined in a population-based case-control study. In addition, we investigated whether recognized risk factors account for the familial aggregation of these cardiovascular events. METHODS AND RESULTS: PCA cases, 25 to 74 years old, attended by paramedics during the period 1988 to 1994 and population-based control subjects matched for age and sex were identified from the community by random digit dialing. All subjects were free of recognized clinical heart disease and major comorbidity. A detailed history of MI and PCA in first-degree relatives was collected in interviews with the spouses of case and control subjects by trained interviewers using a standardized questionnaire. For each familial relationship, there was a higher rate of MI or primary cardiac arrest (MI/PCA) in relatives of case compared with relatives of control subjects. Overall, the rate of MI/PCA among first-degree relatives of cardiac arrest patients was almost 50% higher than that in first-degree relatives of control subjects (rate ratio [RR]=1.46; 95% CI=1.23 to 1.72). In a multivariate logistic model, family history of MI/PCA was associated with PCA (RR=1.57; 95% CI=1.27 to 1.95) even after adjustment for other common risk factors. CONCLUSIONS: Family history of MI or PCA is positively associated with the risk of primary cardiac arrest. This association is mostly independent of familial aggregation of other common risk factors.

Caffeine intake in relation to the risk of primary cardiac arrest.

We conducted a population-based case-control study in King County, WA, to evaluate the association between usual caffeine intake and primary cardiac arrest. We identified primary cardiac arrest cases (N = 362) without a history of clinical heart disease or major comorbidity through paramedic incident reports during the period 1988-1994. We identified controls (N = 581), individually matched to cases on age (+/-7 years) and gender and meeting the same general health criteria, through random digit dialing. We interviewed the spouses of cases and controls to obtain information on usual caffeine intake from coffee, tea, and cola during the prior year. After adjusting for cigarette smoking and other risk factors, we observed little association between daily consumption of the caffeine equivalent of fewer than 5 cups per day of drip coffee (< 687 mg per day) and primary cardiac arrest. High usual caffeine consumption (> or = 687 mg per day) was associated with a modestly elevated risk of primary cardiac arrest [odds ratio = 1.44; 95% confidence interval (CI) = 0.82-2.53]. The elevated risk associated with high caffeine consumption appeared to be restricted to never-smokers (odds ratio for > or = 687 mg per day = 3.2; 95% CI = 1.3-8.1).

Data collection and retrieval to document the outcomes of cardiopulmonary resuscitation.

In this presentation from the Wolf Creek IV Conference, the panel reviewed data requirements for documenting the processes and outcomes associated with the treatment of out-of-hospital cardiac arrest. It was recognized that this was a multifaceted task and that at least three areas warrant consideration: a) emergency medical services system management, b) monitoring and improving the quality of care, and c) the establishment of databases for research. There was complete agreement that the desired outcome is the victim's survival with intact neurologic function. However, the means of improving outcome, short of speedy initiation of treatment, were less clear. It was suggested that the Utstein guidelines, modified for practicability, can serve as a framework to characterize the arrest and to describe the temporal aspect of interventions. However, it was recognized that there were major deficits in understanding the importance of specific interventions, including their timing. Additionally, means to evaluate the quality of care delivered on the scene are usually wanting. The availability of recording electrocardiograms with accompanying voice was regarded as a major opportunity to better monitor the care that was delivered at the scene. Some of the problems incurred with cardiopulmonary resuscitation research in animals were discussed.

Plasma thyroid hormone profiles immediately following out-of-hospital cardiac arrest.

Previous studies have shown abnormal thyroid hormone profiles during cardiac arrest. We explored this association further by characterizing plasma thyroid hormone profiles in 473 patients with out-of-hospital cardiac arrest and correlating them with clinical outcomes. Paramedics collected blood at the end of attempted resuscitation regardless of success. Bloods were collected and processed in a similar manner from 18 control subjects randomly selected from the community. Total thyroxine and total triiodothyronine were lower and reverse triiodothyronine and thyrotropin were higher in cardiac arrest patients than control subjects (all p < 0.001). Except for reverse triiodothyronine, findings were similar for a subgroup of cardiac arrest patients considered to be previously healthy (n = 30). Being discharged alive was associated with total thyroxine, total triiodothyronine and reverse triiodothyronine concentrations closer to the control range and thyrotropin concentrations farther from it, namely higher. In a multivariate stepwise model, only total triiodothyronine and thyrotropin were significantly associated with outcome. Whether these profoundly abnormal profiles represent a pre-existing state or a sudden change of thyroid hormone concentrations cannot be answered with this retrospective study. These observations suggest that thyroid hormones may play a role in the etiology of cardiac arrest, its prognosis, or both.

Clinically silent electrocardiographic abnormalities and risk of primary cardiac arrest among hypertensive patients.

BACKGROUND: Whether continuous ECG indexes that reflect the severity of left ventricular hypertrophy (LVHI), myocardial injury (CIIS), and QT-interval prolongation (QTI) are associated with the risk of primary cardiac arrest among hypertensive patients, independent of conventional binary ECG criteria, remains unknown. METHODS AND RESULTS: We conducted a population-based case-control study among patients who were free of clinically recognized heart disease and who received care at a health maintenance organization. Cases (n = 131) were treated hypertensive patients who had had a primary cardiac arrest between 1977 and 1990. Controls (n = 562) were a stratified random sample of treated hypertensive patients. Resting ECGs were reviewed to estimate the severity of left ventricular hypertrophy, myocardial injury, and QT-interval prolongation on the basis of the algorithms of the Novacode ECG classification system. After adjustment for other risk factors and binary ECG criteria for the abnormalities, the LVHI, CIIS, and QTI scores were directly related to the risk of primary cardiac arrest. In a comparison of the 80th with the 20th percentile score for the LVHI, the risk was increased 40% (odds ratio, 1.4; 95% CI, 1.0 to 2.0); for the CIIS, the risk was increased 70% (odds ratio, 1.7; 95% CI, 1.2 to 2.5); and for the QTI, the risk was increased 80% (odds ratio, 1.8; 95% CI, 1.3 to 2.7). CONCLUSIONS: Our findings suggest that continuous ECG indexes that reflect left ventricular hypertrophy, myocardial injury, and QT-interval prolongation are directly related to the risk of primary cardiac arrest among hypertensive patients without clinically recognized heart disease. Binary ECG criteria may underestimate the prognostic importance of these pathophysiological abnormalities.