Prolonged QT and myocardium recovery after primary PCI: a cMRI study

Temporal electrocardiographic changes in anterior ST elevation myocardial infarction versus the Takotsubo syndrome

Background

Electrocardiography (ECG) on admission is similar in ST elevation myocardial infarction (STEMI) and Takotsubo syndrome (TTS). ECG on admission has been extensively investigated and compared between STEMI and TTS, however, only a few studies have compared temporal ECG. Our aim was to compare ECG in anterior STEMI versus female TTS from admission to day 30.

Methods

Adult patients with anterior STEMI or TTS treated at Sahlgrenska University Hospital (Gothenburg, Sweden) from December 2019 to June 2022 were prospectively enrolled. Baseline characteristics, clinical variables and ECGs from admission to day 30 were analyzed. Using a mixed effects model, we compared temporal ECG between female patients with anterior STEMI or TTS, as well as between female and male patients with anterior STEMI.

Results

A total of 101 anterior STEMI patients (31 female, 70 male) and 34 TTS patients (29 female, 5 male) were included. The temporal pattern of T wave inversion was similar between female anterior STEMI and female TTS, as well as between female and male anterior STEMI. ST elevation was more common, whereas QT prolongation was less common, in anterior STEMI compared with TTS. Q wave pathology was more similar between female anterior STEMI and female TTS than between female and male anterior STEMI.

Conclusions

The pattern of T wave inversion and Q wave pathology from admission to day 30 was similar in female patients with anterior STEMI and female patients with TTS. Temporal ECG in female patients with TTS may be interpreted as following a "transient ischemic" pattern.

Prolonged repolarization in the early phase of ischemia is associated with ventricular fibrillation development in a porcine model

Background: Repolarization prolongation can be the earliest electrophysiological change in ischemia, but its role in arrhythmogenesis is unclear. The aim of the present study was to evaluate the early ischemic action potential duration (APD) prolongation concerning its causes, expression in ECG and association with early ischemic ventricular fibrillation (phase 1A VF). Methods: Coronary occlusion was induced in 18 anesthetized pigs, and standard 12 lead ECG along with epicardial electrograms were recorded. Local activation time (AT), end of repolarization time (RT), and activation-repolarization interval (ARIc) were determined as dV/dt minimum during QRS-complex, dV/dt maximum during T-wave, and rate-corrected RT-AT differences, respectively. Patch-clamp studies were done in enzymatically isolated porcine cardiomyocytes. IK(ATP) activation and Ito1 inhibition were tested as possible causes of the APD change. Results: During the initial period of ischemia, a total of 11 pigs demonstrated maximal ARIc prolongation >10 ms at 1 and/or 2.5 min of occlusion (8 and 6 cases at 1 and 2.5 min, respectively) followed by typical ischemic ARIc shortening. The maximal ARIc across all leads was associated with VF development (OR 1.024 95% CI 1.003-1.046, p = 0.025) and maximal rate-corrected QT interval (QTc) (B 0.562 95% CI 0.346-0.775, p < 0.001) in logistic and linear regression analyses, respectively. Phase 1A VF incidence was associated with maximal QTc at the 2.5 min of occlusion in ROC curve analysis (AUC 0.867, p = 0.028) with optimal cut-off 456 ms (sensitivity 1.00, specificity 0.778). The pigs having maximal QTc at 2.5 min more and less than 450 ms significantly differed in phase 1A VF incidence in Kaplan-Meier analysis (log-rank p = 0.007). In the patch-clamp experiments, 4-aminopyridine did not produce any effects on the APD; however, pinacidil activated IK(ATP) and caused a biphasic change in the APD with initial prolongation and subsequent shortening. Conclusion: The transiently prolonged repolarization during the initial period of acute ischemia was expressed in the prolongation of the maximal QTc interval in the body surface ECG and was associated with phase 1A VF. IK(ATP) activation in the isolated cardiomyocytes reproduced the biphasic repolarization dynamics observed in vivo, which suggests the probable role of IK(ATP) in early ischemic arrhythmogenesis.

Synthetic recovery of impulse propagation in myocardial infarction via silicon carbide semiconductive nanowires

Myocardial infarction causes 7.3 million deaths worldwide, mostly for fibrillation that electrically originates from the damaged areas of the left ventricle. Conventional cardiac bypass graft and percutaneous coronary interventions allow reperfusion of the downstream tissue but do not counteract the bioelectrical alteration originated from the infarct area. Genetic, cellular, and tissue engineering therapies are promising avenues but require days/months for permitting proper functional tissue regeneration. Here we engineered biocompatible silicon carbide semiconductive nanowires that synthetically couple, via membrane nanobridge formations, isolated beating cardiomyocytes over distance, restoring physiological cell-cell conductance, thereby permitting the synchronization of bioelectrical activity in otherwise uncoupled cells. Local in-situ multiple injections of nanowires in the left ventricular infarcted regions allow rapid reinstatement of impulse propagation across damaged areas and recover electrogram parameters and conduction velocity. Here we propose this nanomedical intervention as a strategy for reducing ventricular arrhythmia after acute myocardial infarction.

Silicon-based materials have the ability to support bioelectrical activity. Here the authors show how injectable silicon carbide nanowires reduce arrhythmias and rapidly restore conduction in a myocardial infarction model.

Measurement of the QT interval using the Apple Watch

The inherited and acquired long QT is a risk marker for potential serious cardiac arrhythmias and sudden cardiac death. Smartwatches are becoming more popular and are increasingly used for monitoring human health. The present study aimed to assess the feasibility and reliability of evaluating the QT interval in lead I, lead II, and V2 lead using a commercially available Apple Watch. One hundred nineteen patients admitted to our Cardiology Division were studied. I, II, and V2 leads were obtained after recording a standard 12-lead ECG. Lead I was recorded with the smartwatch on the left wrist and the right index finger on the crown. Lead II was obtained with the smartwatch on the left lower abdomen and the right index finger on the crown. The V2 lead was recorded with the smartwatch in the fourth intercostal space left parasternal with the right index finger on the crown. There was agreement among the QT intervals of I, II, and V2 leads and the QT mean using the smartwatch and the standard ECG with Spearman’s correlations of 0.886; 0.881; 0.793; and 0.914 (p < 0.001), respectively. The reliability of the QTc measurements between standard and smartwatch ECG was also demonstrated with a Bland–Altman analysis using different formulas. These data show that a smartwatch can feasibly and reliably assess QT interval. These results could have an important clinical impact when frequent QT interval monitoring is required.

Risk of in-hospital life-threatening ventricular arrhythmia or death after ST-elevation myocardial infarction vs. the Takotsubo syndrome

Aims

The risk of life‐threatening ventricular arrhythmias (LTVA) has been reported to be lower in Takotsubo syndrome (TS) compared with ST‐elevation myocardial infarction (STEMI). However, the extent to which these differences relate to the fact that most patients with TS are women (who have a lower risk of LTVA) and a relatively larger proportion of patients with STEMI are men is incompletely understood. We aimed to investigate the risk of LTVA or death in sex‐matched and age‐matched patients with TS, anterior STEMI, and non‐anterior STEMI.

Methods and results

We systematically reviewed the charts of all patients with TS who were treated at Sahlgrenska University Hospital (Gothenburg, Sweden) between 2008 and 2019. A total of 155 patients with confirmed TS (according to the European Society of Cardiology diagnostic criteria for TS) were sex‐matched and age‐matched 1:1:1 to patients with anterior and non‐anterior STEMI. Baseline characteristics and in‐hospital outcomes were recorded directly from the patient charts for all patients, and all admission electrocardiographs were analysed. The primary outcome was the composite of death or LTVA [defined as sustained ventricular tachycardia (>30 s) or ventricular fibrillation] within 72 h. The risk of LTVA or death within 72 h after admission was considerably lower in TS (2.6%) vs. anterior STEMI (14%; P = 0.002) and non‐anterior STEMI (9.0%; P = 0.02), despite similar or greater risks of acute heart failure, and similar risks of cardiogenic shock. Compared with STEMI, TS was associated with a lower risk of sustained and non‐sustained ventricular tachycardia and ventricular fibrillation.

Conclusions

In a predominantly female age‐matched and sex‐matched cohort of patients with TS, anterior STEMI, and non‐anterior STEMI, the adjusted risk of in‐hospital LTVA or death was considerably lower in TS compared with STEMI, despite similar or greater risk of acute heart failure and similar risk of cardiogenic shock.

Comparison of QT dispersion in patients with ST elevation acute myocardial infarction (STEMI) before and after treatment by streptokinase versus primary percutaneous coronary intervention (PCI)

Background

QT dispersion (QTD) represents inhomogeneous ventricular repolarization such that an increased QTD may predispose the heart to malignant ventricular arrhythmias (VAs). This study was conducted to compare QTD in patients with ST-elevation myocardial infarction (STEMI) before and after treatment by streptokinase (SK) versus primary percutaneous coronary intervention (PCI).

Methods

The present case–control study was conducted on 185 STEMI patients who received SK (115 cases) or underwent primary PCI (70 cases). QTD and QT corrected dispersion before and 24 h after treatment. Likewise, they were also found to correct fatal arrhythmias (VT and VF) during the first 24 h after admission, and ejection fraction (EF) 24 h after treatment was evaluated.

Results

QTD decreased in the primary PCI group, though no significant difference was seen between the two studied groups (P > 0.05). A significant increase was detected in the EF mean values for the primary PCI-treated patients (P = 0.022). Moreover, there was a significant reduction in QTD of patients with fatal arrhythmias in the primary PCI group (P = 0.022).

Conclusion

An overall QTD reduction in the primary PCI group and a significant decrease in QTD of patients with fatal arrhythmias in the primary PCI group show that this treatment strategy is more efficient than thrombolytic therapy. As an important indicator of proper myocardial function, EF can independently predict improved myocardial function in the primary PCI group.