This novel cumulative ECG risk score was independently associated with SCD and was particularly effective for LVEF >35% where risk stratification is currently unavailable. These findings warrant further evaluation in prospective clinical investigations.
Sports was a trigger of SCA in a minority of cases, and, in most patients, SCA occurred without warning symptoms. Standard cardiovascular risk factors were found in over half of patients, suggesting the potential role of public health approaches that screen for cardiovascular risk factors at earlier ages.
Background
The Tpeak-to-Tend interval (Tpe) on the 12-lead electrocardiogram (ECG) predicts increased risk of sudden cardiac arrest (SCA). There is controversy on whether Tpe would be more useful if corrected for heart rate (Tpec).
Objective
We evaluate if the predictive value of Tpe for SCA improves with heart rate correction and determine an optimal cut-off value for Tpec in the context of SCA risk.
Methods
Cases of SCA (n=628; mean age 66.4±14.5years; 66.2% males) from the Oregon Sudden Unexpected Death Study with an archived ECG available prior and unrelated to the SCA event, were analyzed. Comparisons were made with control subjects (n=819; mean age 66.7±11.5years; 68.2% males). The Tpe interval was corrected for heart rate using Bazett (TpecBa) and Fridericia (TpecFd) formulae, and the predictive value of Tpec for SCA was evaluated in logistic regression models.
Results
The area-under-curve (AUC) for Tpec predicting SCA improved with both correction formulae. Tpec using the Bazett and Fridericia formulae were shown to have an AUC of 0.695 and 0.672 respectively compared to a baseline of 0.601 with an uncorrected Tpe. TpecBa >90ms was predictive of SCA independent of age, gender, comorbidities, QRS duration, QTc and severely reduced left ventricular ejection fraction [LVEF≤35%; OR 2.8 (95% CI, 1.92 to 4.17; p<0.0001)].
Conclusion
Correcting the Tpe for heart rate, using either the Bazett or Fridericia formulae, improved the independent predictive value of this marker for assessment of SCA risk. Prolongation of TpecBa beyond 90ms was associated with a nearly 3-fold increased risk of SCA.
Objective
To evaluate the potential role of low serum calcium (Ca) levels toward occurrence of SCA in the community.
Patients and Methods
We compared 267 SCA cases (73% male) and 445 controls (71% male) from a large population based study (catchment population almost 1 million) in the US Northwest from February 1st, 2002 to December 31st, 2015. Subjects were included if their age was ≥18 years with available creatinine clearance (CrCl) and serum electrolyte levels for analyses, to enable adjustment for renal function. For cases, CrCl and electrolytes were required to be measured within 90 days of the SCA event.
Results
Cases of SCA had higher proportions of African-Americans (12% vs. 3%, P<.001), diabetes mellitus (46% vs. 28%, P<.001) and chronic kidney disease (38% vs. 16%, P<.001) compared to controls. In multivariable logistic regression analysis, a one-unit decrease in Ca level was associated with 1.6-fold increase in odds of SCA (odds ratio [OR] =1.63, 95% confidence interval [CI]: 1.06–2.51). Blood Ca levels lower than 8.95 mg/dL were associated with 2.3-fold increase in odds of SCA comparing to levels higher than 9.55 mg/dL (OR= 2.33, 95% CI: 1.17–4.61). SCA cases had significantly prolonged QTc intervals on the 12-lead ECG compared to controls (465±37 ms vs. 425±33 ms, P<.001).
Conclusions
Lower serum Ca levels were independently associated with increased risk of SCA in the community.
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