Lung function, percent emphysema, and QT duration: The Multi-Ethnic Study of Atherosclerosis (MESA) lung study

Automated Quantification of QT-Intervals by an Algorithm: A Validation Study in Patients with Chronic Obstructive Pulmonary Disease

Study Objectives

To assess the diagnostic accuracy of a purpose-designed QTc-scoring algorithm versus the established hand-scoring in patients with chronic obstructive pulmonary disease (COPD) undergoing sleep studies.

Methods

We collected 62 overnight electrocardiogram (ECG) recordings in 28 COPD patients. QT-intervals corrected for heart rate (QTc, Bazett) were averaged over 1-min periods and quantified, both by the algorithm and by cursor-assisted hand-scoring. Hand-scoring was done blinded to the algorithm-derived results. Bland-Altman statistics and confusion matrixes for three thresholds (460, 480, and 500ms) were calculated.

Results

A total of 32944 1-min periods and corresponding mean QTc-intervals were analysed manually and by computer. Mean difference between manual and algorithm-based QTc-intervals was -1ms, with limits of agreement of -18 to 16ms. Overall, 2587 (8%), 357 (1%), and 0 QTc-intervals exceeding the threshold 460, 480, and 500ms, respectively, were identified by hand-scoring. Of these, 2516, 357, and 0 were consistently identified by the algorithm. This resulted in a diagnostic classification accuracy of 0.98 (95% CI 0.98/0.98), 1.00 (1.00/1.00), and 1.00 (1.00/1.00) for 460, 480, and 500ms, respectively. Sensitivity was 0.97, 1.00, and NA for 460, 480, and 500ms, respectively. Specificity was 0.98, 1.00, and 1.00 for 460, 480, and 500ms, respectively.

Conclusion

Overall, 8% of nocturnal 1-min periods showed clinically relevant QTc prolongations in patients with stable COPD. The automated QTc-algorithm accurately identified clinically relevant QTc-prolongations with a very high sensitivity and specificity. Using this tool, hospital sleep laboratories may identify asymptomatic patients with QTc-prolongations at risk for malignant arrhythmia, allowing them to consult a cardiologist before an eventual cardiac event.

High-Throughput Assessment of Real-World Medication Effects on QT Interval Prolongation: Observational Study

BACKGROUND

Drug-induced prolongation of the corrected QT interval (QTc) increases the risk for Torsades de Pointes (TdP) and sudden cardiac death. Medication effects on the QTc have been studied in controlled settings but may not be well evaluated in real-world settings where medication effects may be modulated by patient demographics and comorbidities as well as the usage of other concomitant medications.

OBJECTIVE

We demonstrate a new, high-throughput method leveraging electronic health records (EHRs) and the Surescripts pharmacy database to monitor real-world QTc-prolonging medication and potential interacting effects from demographics and comorbidities.

METHODS

We included all outpatient electrocardiograms (ECGs) from September 2008 to December 2019 at a large academic medical system, which were in sinus rhythm with a heart rate of 40-100 beats per minute, QRS duration of <120 milliseconds, and QTc of 300-700 milliseconds, determined using the Bazett formula. We used prescription information from the Surescripts pharmacy database and EHR medication lists to classify whether a patient was on a medication during an ECG. Negative control ECGs were obtained from patients not currently on the medication but who had been or would be on that medication within 1 year. We calculated the difference in mean QTc between ECGs of patients who are on and those who are off a medication and made comparisons to known medication TdP risks per the CredibleMeds.org database. Using linear regression analysis, we studied the interaction of patient-level demographics or comorbidities on medication-related QTc prolongation.

RESULTS

We analyzed the effects of 272 medications on 310,335 ECGs from 159,397 individuals. Medications associated with the greatest QTc prolongation were dofetilide (mean QTc difference 21.52, 95% CI 10.58-32.70 milliseconds), mexiletine (mean QTc difference 18.56, 95% CI 7.70-29.27 milliseconds), amiodarone (mean QTc difference 14.96, 95% CI 13.52-16.33 milliseconds), rifaximin (mean QTc difference 14.50, 95% CI 12.12-17.13 milliseconds), and sotalol (mean QTc difference 10.73, 95% CI 7.09-14.37 milliseconds). Several top QT prolonging medications such as rifaximin, lactulose, cinacalcet, and lenalidomide were not previously known but have plausible mechanistic explanations. Significant interactions were observed between demographics or comorbidities and QTc prolongation with many medications, such as coronary disease and amiodarone.

CONCLUSIONS

We demonstrate a new, high-throughput technique for monitoring real-world effects of QTc-prolonging medications from readily accessible clinical data. Using this approach, we confirmed known medications for QTc prolongation and identified potential new associations and demographic or comorbidity interactions that could supplement findings in curated databases. Our single-center results would benefit from additional verification in future multisite studies that incorporate larger numbers of patients and ECGs along with more precise medication adherence and comorbidity data.

QT interval instability and variability in dogs with naturally-occurring hypercortisolism

Hypercortisolism is one of the most common endocrine diseases in dogs. In humans, it is clearly associated with a higher risk of cardiovascular events, but studies in dogs are scarce. To investigate the arrhythmogenic risk of dogs with naturally-occurring hypercortisolism (NOHC), indices of variability and instability of the QT interval were retrospectively studied in 38 dogs with NOHC and prospectively studied in 12 healthy dogs: variance (QTv), total instability (TI), short-term (STI) and long-term (LTI), and mean (QTm). Except for QTm, all parameters studied were higher in the NOHC group than in the control group. In addition, STI and QTv showed moderate positive correlation with left ventricle wall thickness. The NOHC group was subdivided according to cortisol suppression pattern in the low-dose dexamethasone suppression test. All electrocardiographic indices of partial and absent suppression patterns were numerically higher than healthy dogs. QTv and TI were lower in the control group than in both NOHC subgroups. LTI and STI were lower in the CG than in the group with the partial suppression pattern. There was no statistical difference between sex groups in any of the electrocardiographic parameters studied. This result might indicate that the etiology of NOHC, and its consequent influence on hypothalamus-pituitary-adrenal axis could interfere on the heterogeneity of ventricular repolarization parameters in different ways, especially in the short-term and the long-term stability; however further studies are necessary to understand the role of cortisol on electrical instability in dogs.

Increasing Daily Physical Activity and Its Effects on QTc Time in Severe to Very Severe COPD: A Secondary Analysis of a Randomised Controlled Trial

Approximately, half of COPD patients die from cardiovascular diseases. A prolongation of cardiac repolarization (measured as QTc interval) is associated with cardiovascular events or cardiovascular deaths in populations of older adults and COPD. One way to reduce the QTc could be to increase physical activity (PA). We investigated whether QTc can be reduced by an increase in PA in patients with severe COPD. This is a secondary outcome analysis from a randomized controlled trial investigating the effects of a 3 months pedometer based program to improve PA. 12-lead ECG was assessed at baseline and after 3 months. We measured PA using a validated triaxial accelerometer. Data were analyzed from 59 participants. Multiple regression modeling, including adjustment for baseline QTc, sex, QT prolonging medications, BMI, smoking status and FEV1%, showed no evidence for an association between an improvement of ≥15% PA and QTc reduction. A 15% improvement in PA according to step counts over 3 months seems not to reduce QTc interval by its MCID of 20 ms in patients with severe to very severe COPD.

Low lung function, sudden cardiac death and non-fatal coronary events in the general population

BACKGROUND

Many of those who suffer from a first acute coronary event (CE) die suddenly during the day of the event, most of them die outside hospital. Poor lung function is a strong predictor of future cardiac events; however, it is unknown whether the pattern of lung function impairment differs for the prediction of sudden cardiac death (SCD) versus non-fatal CEs. We examined measures of lung function in relation to future SCD and non-fatal CE in a population-based study.

METHODS

Baseline spirometry was assessed in 28 584 middle-aged subjects, without previous history of CE, from the Malmö Preventive Project. The cohort was followed prospectively for incidence of SCD (death on the day of a first CE, inside or outside hospital) or non-fatal CE (survived the first day). A modified version of the Lunn McNeil's competing risk method for Cox regression was used to run models for both SCD and non-fatal CE simultaneously.

RESULTS

A 1-SD reduction in forced expiratory volume in 1 s (FEV₁) was more strongly associated with SCD than non-fatal CE even after full adjustment (FEV₁: HR for SCD: 1.23 (1.15 to 1.31), HR for non-fatal CE 1.08 (1.04 to 1.13), p value for equal associations=0.002). Similar associations were found for forced vital capacity (FVC) but not FEV₁/FVC. The results remained significant even in life-long never smokers (FEV₁: HR for SCD: 1.34 (1.15 to 1.55), HR for non-fatal CE: 1.11 (1.02 to 1.21), p value for equal associations=0.038). Similar associations were seen when % predicted values of lung function measures were used.

CONCLUSIONS

Low FEV₁ is associated with both SCD and non-fatal CE, but consistently more strongly associated with future SCD. Measurement with spirometry in early life could aid in the risk stratification of future SCD. The results support the use of spirometry for a global assessment of cardiovascular risk.

COPD maintenance medication is linked to left atrial size: Results from the COSYCONET cohort

BACKGROUND

Lung function impairment in COPD is known to be related to reductions of left heart size, while short-term interventional trials with bronchodilators showed positive effects on cardiac parameters. We investigated whether COPD maintenance therapy has analogous long-term effects.

METHODS

Pooled data of GOLD grade 1-4 patients from visits 1 and 3 (1.5 y apart) of the COSYCONET cohort were used. Medication was categorized as use of ICS, LABA + ICS, LABA + LAMA and triple therapy (LABA + LAMA + ICS), contrasting "always" versus "never". Echocardiographic parameters comprised left ventricular end-diastolic and -systolic diameter (LVEDD, LVESD), ejection fraction (LVEF) and left atrial diameter (LA). Associations were identified by multiple regression analysis, as well as propensity score analysis.

RESULTS

Overall, 846 patients (mean age 64.5 y; 41% female) were included, 53% using ICS at both visits, 51% LABA + ICS, 56% LABA + LAMA, 40% LABA + LAMA + ICS (triple) therapy. Conversely, 30%, 32%, 28% and 42% had no ICS, LABA + ICS, LABA + LAMA or triple therapy, respectively, at both visits. Among echocardiographic measures, only LA showed statistically significant associations (increases) with medication, whereby significant effects were linked to ICS, LABA + ICS and LABA + LAMA (p < 0.05 each, "always" versus "never") and propensity score analyses underlined the role of LABA + LAMA.

CONCLUSIONS

In this observational study, COPD maintenance therapy, especially LABA + LAMA, was linked to left atrial size, consistent with the results of short-term interventional trials. These findings suggest that maintenance medication for COPD does not only improve lung function and patient reported outcomes but may also have an impact on the cardiovascular system.

TRIAL REGISTRATION

NCT01245933.

ECG changes at rest and during exercise in lowlanders with COPD travelling to 3100 m

BACKGROUND

The incidence and magnitude of cardiac ischemia and arrhythmias in patients with chronic obstructive pulmonary disease (COPD) during exposure to hypobaric hypoxia is insufficiently studied. We investigated electrocardiogram (ECG) markers of ischemia at rest and during incremental exercise testing (IET) in COPD-patients travelling to 3100 m.

STUDY DESIGN AND METHODS

Lowlanders (residence <800 m) with COPD (forced volume in the first second of expiration (FEV₁) 40-80% predicted, oxygen saturation (SpO₂) ≥92%, arterial partial pressure of carbon dioxide (PaCO₂) <6 kPa at 760 m) aged 18 to 75 years, without history of cardiovascular disease underwent 12‑lead ECG recordings at rest and during cycle IET to exhaustion at 760 m and after acute exposure of 3 h to 3100 m. Mean ST-changes in ECGs averaged over 10s were analyzed for signs of ischemia (≥1 mm horizontal or downsloping ST-segment depression) at rest, peak exercise and 2-min recovery.

RESULTS

80 COPD-patients (51% women, mean ± SD, 56.2 ± 9.6 years, body mass index (BMI) 27.0 ± 4.5 kg/m², SpO₂ 94 ± 2%, FEV₁ 63 ± 10% prEd.) were included. At 3100 m, 2 of 53 (3.8%) patients revealed ≥1 mm horizontal ST-depression during IET vs 0 of 64 at 760 m (p = 0.203). Multivariable mixed regression revealed minor but significant ST-depressions associated with altitude, peak exercise or recovery and rate pressure product (RPP) in multiple leads.

CONCLUSION

In this study, ECG recordings at rest and during IET in COPD-patients do not suggest an increased incidence of signs of ischemia with ascent to 3100 m. Whether statistically significant ST changes below the standard threshold of clinical relevance detected in multiple leads reflect a risk of ischemia during prolonged exposure remains to be elucidated.

Fifty Years of Progress in the Epidemiology of Chronic Obstructive Pulmonary Disease: A Review of National Heart, Lung, and Blood Institute-Sponsored Studies

Our understanding of the epidemiology of chronic obstructive pulmonary disease (COPD), including such metrics as incidence, prevalence, risk factors, outcome, and comorbidities has increased greatly over the past 50 years. Much of this increase is attributable to National Heart Blood and Lung Institute (NHLBI)-sponsored studies. This paper will review 13 of these key studies and their contribution to our understanding of COPD in the last half century.

Long QT and death in hospitalized patients with acute exacerbation of chronic obstructive pulmonary disease is not related to electrolyte disorders

Objectives: COPD is the fourth-leading cause of mortality worldwide. Prolonged QTc has been found to be a long-term negative prognostic factor in ambulatory COPD patients. The aim of this study was to evaluate the extent of prolonged-QTc syndrome in COPD patients upon admission to an internal medicine department, its relationship to hypomagnesemia, hypokalemia, and hypocalcemia, and the effect of COPD treatment on mortality during hospital stay.

Methods: This prospective cohort study evaluated COPD patients hospitalized in an internal medicine department. The study evaluated QTc, electrolyte levels, and known risk factors during hospitalization of COPD patients.

Results: A total of 67 patients were recruited. The median QTc interval was 0.441 seconds and 0.434 seconds on days 0 and 3, respectively. Prolonged QTc was noted in 35.8% of patients on admission and 37.3% on day 3 of hospitalization. The median QTc in the prolonged-QTc group on admission was 0.471 seconds and in the normal-QTc group 0.430 seconds. There was no significant difference in age, sex, electrolyte levels, renal function tests, or blood gases on admission between the two groups. Mortality during the hospital stay was significantly higher in the prolonged-QTc group (3 deaths, 12%) than in the normal QTc group (no deaths) (P=0.04). A subanalysis was performed, removing known causes for prolonged QTc. We found no differences in age, electrolytes, or renal functions. There was a small but significant difference in bicarbonate levels.

Conclusion: Our findings demonstrated that there was no correlation between QTc prolongation in hospitalized COPD patients and electrolyte levels, comorbidities, or relevant medications. A higher rate of mortality was noted in patients with prolonged QTc in comparison to normal QTc. As such, it is suggested that prolonged QTc could serve as a negative prognostic factor for mortality during hospitalization in COPD patients.