Factors associated with the occurrence of cardiac arrest during hospitalization for acute myocardial infarction in the second national registry of myocardial infarction in the US.

Cardiac arrest can occur as a complication of acute myocardial infarction (AMI). To date, few studies have described factors associated with cardiac arrest occurrence and survival during hospitalization for treatment of AMI. We used data from a large national registry of hospitalized AMI patients to identify these factors. Data were collected from 1073 participating institutions, representing 14.4% of US hospitals. Hospital site coordinators conducted periodic chart reviews for AMI patients and data were submitted to an independent center for periodic review. Univariate analysis and multivariate logistic regression were used to identify factors associated with cardiac arrest. We found that cardiac arrest occurred in 4.8% (14,725/305,812) of hospitalized AMI patients. The survival rate to hospital discharge for these individuals was 29.4%. Sustained ventricular tachycardia or fibrillation (VT/VF) was present in 34.7% and was associated with a higher rate of survival to hospital discharge compared to cardiac arrest patients without a ventricular tachyarrhythmia (47.5 vs. 19.8%, P < 0.00001). Hypotension (initial systolic BP < 90 mmHg), q-wave AMI, old age, heart failure and initial heart rate abnormalities (bradycardia or tachycardia) were associated with a higher prevalence of cardiac arrest. A higher percentage of women compared to men experienced cardiac arrest (6.0 vs. 4.41%, P < 0.0001). Cardiac arrest prevalence was lower in patients with inferior wall infarction than in other types of ST-elevation infarction. Use of reperfusion therapy (PTCA or tPA) was associated with improved survival compared to hospitalized AMI patients who did not receive such therapy.

Measurement of oxygen consumption on-kinetics during exercise: implications for patients with heart failure.

Oxygen consumption (VO(2)) on-kinetics describes the rate change in oxygen uptake at the initiation of exercise. Several mathematical and graphical methods are used to assess VO(2) on-kinetics during constant-load or progressive exercise. VO(2) on-kinetics is prolonged in patients with heart failure (HF) compared with individuals who have normal cardiopulmonary function. Cardiac function has been implicated as one of the controlling mechanism for this observation. The contribution that pulmonary, vascular, and skeletal muscle function makes to delayed VO(2) on-kinetics in HF has yet to be determined. VO(2) on-kinetics also appears to have clinical value in HF, although evidence supporting this claim is limited. Questions about the controlling mechanism(s) and practical application of VO(2) on-kinetics in HF therefore remain unanswered. This report provides an overview of VO(2) on-kinetics assessment techniques, reviews research pertaining to the HF population, and provides direction for future investigations.

Safety and efficacy of exercise training in a patient awaiting heart transplantation while on positive intravenous inotropic support.

The safety and efficacy of exercise training in patients with congestive heart failure (CHF) is well established; however, the impact that exercise has on the subgroup of CHF patients awaiting heart transplant while on intravenous positive inotropic support remains largely unreported. This case study describes the safety and efficacy of exercise training in a patient awaiting heart transplant while on intravenous milrinone. Over a 1.2-year period, 246 exercise sessions were conducted with a total of 180.15 hours of aerobic exercise. During that time, the patient experienced only one hypotensive episode during exercise and had no other adverse events. The patient demonstrated a 38% increase in aerobic exercise time and a 34% increase in sustainable exercise workload. Research is needed to demonstrate the positive impact of exercise training on this subgroup of CHF patients.

Synchronization of timepieces to the atomic clock in an urban emergency medical services system.

STUDY OBJECTIVE: Erroneous time documentation of emergency treatment caused by the variation in the accuracy of timepieces has profound medical, medicolegal, and research consequences. The purpose of this study was to confirm the variation of critical timepiece settings in an urban emergency care system noted in previous studies and to implement and monitor the results of a prospective program to improve time synchronization. METHODS: Timepieces (n = 393) used by firefighters, paramedics, and emergency physicians and nurses were randomly sampled immediately before and at two time intervals (1 and 4 months) after attempted synchronization to the US atomic clock standard. The setting on each timepiece was compared with the atomic clock. From the data, a mathematical simulation estimated the number of time-related documentation errors that would occur in 2,500 simulated cardiac arrest cases using timepieces with accuracy similar to those found in the EMS system before and after attempted synchronization. RESULTS: Before attempted synchronization, the timepieces had a mean error of 2.0 (95% confidence interval 1.8 to 2.3) minutes. One month after attempted synchronization, the mean error decreased significantly to .9(.8 to 1.1) minute. However, it increased to 1.7 (1.5 to 1.9) minutes within 4 months. Mathematical simulation before attempted synchronization predicted that 93% of cardiac arrest cases would contain a documentation error of 2 minutes or more and that 41% of cases would contain a documentation error of 5 minutes or more. Attempted synchronization cut the 2-minute documentation error rate in half and reduced the 5-minute documentation error rate by three fourths. However, the error rates were predicted to return to baseline 4 months after attempted synchronization. CONCLUSION: Emergency medical timepieces are often inaccurate, making it difficult to reconstruct events for medical, medicolegal, or research purposes. Community synchronization of timepieces to the atomic clock can reduce the problem significantly, but the effects of a one-time attempted synchronization event are short-lived.

Seasonal pattern of acute myocardial infarction in the National Registry of Myocardial Infarction.

OBJECTIVES: The purpose of this study was to determine whether the rate of hospital admission for acute myocardial infarction (AMI) varies seasonally in a large, prospective U.S. registry. BACKGROUND: Identification of specific patterns in the timing of the onset of AMI is of importance because it implies that there are triggers external to the atherosclerotic plaque. Using death certificate data, most investigators have noted a seasonal pattern to the death rate from AMI. However, it is unclear whether this observation is due to variation in the prevalence of AMI or to other factors that may alter the likelihood of a fatal outcome. METHODS: We examined the seasonal mean number of cases of AMI (adjusted for the length of days in each season) that were submitted to the National Registry of Myocardial Infarction (NRMI) by 138 high volume core hospitals over a 3-year period (December 21, 1990 through December 20, 1993) during which the number of hospitals participating in the Registry was stable. Data were analyzed using general linear modeling and analysis of variance. RESULTS: High volume core hospitals reported 83,541 cases of AMI to the Registry during the study period. Approximately 10% more such cases were entered into the Registry in winter or spring than in summer (p < 0.05). The same trends were seen in both northern and southern states, men and women, patients < 70 versus > or = 70 years of age and those with Q wave versus non-Q wave AMI. CONCLUSIONS: We conclude that there is a seasonal pattern to the reporting rate of cases of AMI in the NRMI. This observation further supports the hypothesis that acute cardiovascular events may be triggered by events that are external to the atherosclerotic plaque.

Recognition of electrocardiographic lead misplacements.

Improper placement of recording electrodes on the skin can generate misleading patterns on the electrocardiogram (ECG). The alterations in the normal ECG caused by lead misplacement were reviewed. Although most clinicians can recognize the common right arm/left arm lead switch that imitates a nonsinus atrial rhythm with high anterolateral myocardial infarction, many other errors are possible. Less common lead placement errors are often difficult to detect. Exchanging the right arm and left leg leads creates what seems to be an inferior wall myocardial infarction and a nonsinus atrial rhythm in normal patients. Reversal of the right arm and right leg connections creates a unique pattern of diffuse low voltage in the limb leads. Precordial lead switches are common and can be recognized by the abnormal R wave progression that is created.