Biological therapy safety in chronic inflammatory arthropathy patients

Short-Term Beat-to-Beat QT Variability Appears Influenced More Strongly by Recording Quality Than by Beat-to-Beat RR Variability

Increases in beat-to-beat variability of electrocardiographic QT interval duration have repeatedly been associated with increased risk of cardiovascular events and complications. The measurements of QT variability are frequently normalized for the underlying RR interval variability. Such normalization supports the concept of the so-called immediate RR effect which relates each QT interval to the preceding RR interval. The validity of this concept was investigated in the present study together with the analysis of the influence of electrocardiographic morphological stability on QT variability measurements. The analyses involved QT and RR measurements in 6,114,562 individual beats of 642,708 separate 10-s ECG samples recorded in 523 healthy volunteers (259 females). Only beats with high morphology correlation (r > 0.99) with representative waveforms of the 10-s ECG samples were analyzed, assuring that only good quality recordings were included. In addition to these high correlations, SDs of the ECG signal difference between representative waveforms and individual beats expressed morphological instability and ECG noise. In the intra-subject analyses of both individual beats and of 10-s averages, QT interval variability was substantially more strongly related to the ECG noise than to the underlying RR variability. In approximately one-third of the analyzed ECG beats, the prolongation or shortening of the preceding RR interval was followed by the opposite change of the QT interval. In linear regression analyses, underlying RR variability within each 10-s ECG sample explained only 5.7 and 11.1% of QT interval variability in females and males, respectively. On the contrary, the underlying ECG noise contents of the 10-s samples explained 56.5 and 60.1% of the QT interval variability in females and males, respectively. The study concludes that the concept of stable and uniform immediate RR interval effect on the duration of subsequent QT interval duration is highly questionable. Even if only stable beat-to-beat measurements of QT interval are used, the QT interval variability is still substantially influenced by morphological variability and noise pollution of the source ECG recordings. Even when good quality recordings are used, noise contents of the electrocardiograms should be objectively examined in future studies of QT interval variability.

Repolarization in systemic sclerosis: a meta-analysis

OBJECTIVES

Systemic sclerosis (SSc) is a rare connective tissue disease characterized by immune dysregulation, vascular damage, and increased deposition of extracellular matrix. In SSc, cardiac manifestations are common and account for 14% of deaths. Numerous studies have examined electrocardiographic findings in SSc patients yielding conflicting reports regarding QTc duration. We conducted a systematic review and meta-analysis of existing studies to investigate whether QTc duration may aid in diagnosis and risk stratification of SSc patients.

METHODS

Two electronic databases (PubMed and Embase) were searched for case-control and cohort studies assessing QTc duration in SSc patients published before March 1, 2021. A random-effects model was used to meta-analyze the results, and included studies were tested for heterogeneity. Linear regression was performed to determine correlations between comorbidities, and QTc duration.

RESULTS

Ninety-six studies, abstracts, and posters were identified. After abstract review and duplicate removal, 23 manuscripts remained. After application of the inclusion and exclusion criteria, 10 studies remained which were quantitatively analyzed. The weighted mean QTc was found to be 422.21 ms for SSc patients and 411.43 ms for control subjects. A significant increase in QTc duration among SSc patients was found, with a standardized mean difference of 0.59 (p < 0.01, 95% CI 0.27-0.92). No significant correlation was found between underlying traits and QTc values. Substantial heterogeneity was found between the studies (I² = 83%, p < 0.01).

CONCLUSION

A significant increase in QTc duration is observed in SSc patients, though the absolute prolongation is not extreme. Therefore, the clinical utility of this finding is unclear and merits large prospective observations. Key Points • A statistically significant prolongation of the QTc interval exists in patients with systemic sclerosis. • Absolute QTc differences between healthy controls and scleroderma patients are not extreme, and, as such, may be of limited clinical utility. • When assessing the underlying traits of systemic sclerosis patients, no statistically significant correlations were found between underlying parameters and QTc duration.

Heart Rate Influence on the QT Variability Risk Factors

QT interval variability, mostly expressed by QT variability index (QTVi), has repeatedly been used in risk diagnostics. Physiologic correlates of QT variability expressions have been little researched especially when measured in short 10-second electrocardiograms (ECGs). This study investigated different QT variability indices, including QTVi and the standard deviation of QT interval durations (SDQT) in 657,287 10-second ECGs recorded in 523 healthy subjects (259 females). The indices were related to the underlying heart rate and to the 10-second standard deviation of RR intervals (SDRR). The analyses showed that both QTVi and SDQT (as well as other QT variability indices) were highly statistically significantly (p < 0.00001) influenced by heart rate and that QTVi showed poor intra-subject reproducibility (coefficient of variance approaching 200%). Furthermore, sequential analysis of regression variance showed that SDQT was more strongly related to the underlying heart rate than to SDRR, and that QTVi was influenced by the underlying heart rate and SDRR more strongly than by SDQT (p < 0.00001 for these comparisons of regression dependency). The study concludes that instead of QTVi, simpler expressions of QT interval variability, such as SDQT, appear preferable for future applications especially if multivariable combination with the underlying heart rate is used.

Electrocardiographic markers for the prediction of ventricular arrhythmias in patients with systemic sclerosis

SSc is an autoimmune disease characterized by microvascular damage, endothelial dysfunction and fibrosis of the skin and the internal organs. Cardiac manifestation in patients with SSc is one of the major organ involvements. Approximately 20% of SSc patients suffer from primary cardiovascular disease and another 20% may have secondary cardiac involvement. Although cardiac arrhythmias are mostly linked to myocardial fibrosis, atrioventricular conduction abnormalities are secondary to the fibrosis of the pulse conduction system. Despite the severe consequences of ventricular rhythm disturbances in patients with SSc, the exact role of electrocardiographic markers in the prediction of these arrhythmias has not yet been clearly elucidated. Therefore, the question is whether certain ECG parameters reflecting ventricular repolarization may help to recognize scleroderma patients with increased risk for ventricular arrhythmias and sudden cardiac death.