MEDICC Review

Increased QT Interval Dispersion in Diagnosis of Acute Coronary Syndrome with Atypical Symptoms and EKG
July–October 2014, Vol 16, No 3–4

INTRODUCTION EKG remains a highly valuable tool for heart disease management. Corrected QT interval dispersion is a useful EKG parameter to assess prognosis in ischemic heart disease and specifically acute coronary syndrome. Understanding QT interval physiopathology helps assess importance of QT measurement in this context. Although increased QT dispersion is an ominous prognostic marker, its utility has not been evaluated for all types of acute coronary syndrome, even though in many circumstances it is the only tool available for diagnosing patients with equivocal EKG signs and/or atypical symptoms.

OBJECTIVE Describe corrected QT interval dispersion in acute coronary syndrome in three groups of patients—with ST elevation, without ST elevation, and without ST elevation with equivocal EKG signs—admitted to the intensive care unit of Celestino Hernández Robau University Hospital in Santa Clara, Cuba, from January 2010 through June 2011.

METHODS A descriptive retrospective study was conducted in 194 patients admitted with diagnosis of acute coronary syndrome. QT interval was measured and its dispersion calculated for the first EKG after symptom onset. Patterns were assessed for typical and atypical clinical presentations, and unequivocal and equivocal EKG signs.

RESULTS Nonclassifiable acute coronary syndrome was found in 6.7% of patients (13/194), the majority of whom had increased QT dispersion (76.9%, 10/13). There were significant differences in QT dispersion patterns between patients with typical and atypical presentations and between patients with equivocal and unequivocal EKG findings. In non-ST elevation acute coronary syndrome and nonclassifiable acute coronary syndrome with increased dispersion, atypical presentation was the most common (65.5%, 19/29; and 90%, 9/10, respectively).

CONCLUSION Corrected QT interval dispersion is a useful diagnostic tool for acute coronary syndrome, especially when patients present with atypical symptoms and equivocal EKG findings. Thus, it is a low-cost alternative in management of acute coronary syndrome in resource-poor settings.

KEYWORDS Risk factors, ischemic heart disease, acute coronary syndrome, myocardial ischemia, electrocardiography, QT interval dispersion, prognosis, Cuba

Acute Myocardial Infarction Incidence, Mortality and Case Fatality in Santa Clara, Cuba, 2007–2008
October 2011, Vol 13, No 4

INTRODUCTION Information on acute myocardial infarction incidence and mortality is essential for determining the efficacy of the health system’s cardiovascular disease prevention activities; however, in Cuba, sufficient data related to acute myocardial infarction are lacking, particularly at the local level.

OBJECTIVE Describe acute myocardial infarction incidence, mortality and case fatality rates from January 2007 through December 2008 in persons aged 45-74 in the municipality of Santa Clara, Villa Clara Province, Cuba.

METHODS A retrospective descriptive study was conducted. The World Health Organization MONItoring Trends and Determinants in CArdiovascular Disease Project (MONICA) methodology was used, but only in part, since out-of-hospital case fatalities were not investigated, resulting in insufficient data for such cases. Cases of acute myocardial infarction covered under MONICA definition 1 were included (non-fatal definite, fatal definite, fatal possible, and unclassifiable deaths). Hospitalized patients were followed for 28 days. Incidence, mortality and case fatality rates in the population were calculated by age group (45–54, 55–64 and 65–74 years) and sex. Age-standardized incidence and mortality rates were calculated using the direct method, with the world population as a reference.

RESULTS A total of 482 cases of acute myocardial infarction were registered. The percentage of cases of non-fatal definite, fatal definite, fatal possible and fatal with insufficient data were 32%, 18.3%, 26.3% and 13.9% respectively. The cumulative age-standardized incidence per 100,000 population was 433 (95% CI 365–501) in men and 195 (95% CI 152–237) in women, while mortality per 100,000 population was 242 (95% CI 192–292) in men and 120 (95% CI 87–153) in women. Case fatality was 56.4% in men and 62.6% in women. Most fatal cases (65.6%) occurred out of hospital, a trend that was more marked in men (73.9%) than in women (51%).

CONCLUSIONS Case fatality from acute myocardial infarction in Santa Clara residents was high, especially in women. Two thirds of fatalities occurred out of hospital, a higher proportion of these deaths in men. It is recommended that the AMI registry be completed by investigating out-of-hospital case fatalities with insufficient data; expanding it to include the 35-44 age group; and that the supply of cardiac marker enzyme immunoassay test kits in Santa Clara be stabilized.

KEYWORDS Myocardial infarction, heart disease, cardiovascular disease, chronic disease, epidemiology, mortality, incidence, surveillance, registries, Cuba