T-Wave Analysis on the 24 h Holter ECG Monitoring as a Predictive Assessment of Major Adverse Cardiovascular Events in Patients with Myocardial Infarction: A Literature Review and Future Perspectives

Myocardial ischemia is a pathophysiological state characterized by inadequate perfusion of the myocardium, resulting in an imbalance between myocardial oxygen demand and supply. It is most commonly caused by coronary artery disease, in which atherosclerotic plaques lead to luminal narrowing and reduced blood flow to the heart. Myocardial ischemia can manifest as angina pectoris or silent myocardial ischemia and can progress to myocardial infarction or heart failure if left untreated. Diagnosis of myocardial ischemia typically involves a combination of clinical evaluation, electrocardiography and imaging studies. Electrocardiographic parameters, as assessed by 24 h Holter ECG monitoring, can predict the occurrence of major adverse cardiovascular events in patients with myocardial ischemia, independent of other risk factors. The T-waves in patients with myocardial ischemia have prognostic value for predicting major adverse cardiovascular events, and their electrophysiological heterogeneity can be visualized using various techniques. Combining the electrocardiographic findings with the assessment of myocardial substrate may offer a better picture of the factors that can contribute to cardiovascular death.

Cardiac monitoring for patients with palpitations

Palpitations are one of the most common reasons for medical consultation. They tend to worry patients and can affect their quality of life. They are often a symptom associated with cardiac rhythm disorders, although there are other etiologies. For diagnosis, it is essential to be able to reliably correlate the symptoms with an electrocardiographic record allowing the identification or ruling out of a possible rhythm disorder. However, reaching a diagnosis is not always simple, given that they tend to be transitory symptoms and the patient is frequently asymptomatic at the time of assessment. In recent years, electrocardiographic monitoring systems have incorporated many technical improvements that solve several of the 24-h Holter monitor limitations. The objective of this review is to provide an update on the different monitoring methods currently available, remarking their indications and limitations, to help healthcare professionals to appropriately select and use them in the work-up of patients with palpitations.

Pericardial Fat Is Associated With the Risk of Ventricular Arrhythmia in Asian Patients

BACKGROUND

Pericardial fat is correlated with the occurrence of atrial fibrillation or coronary atherosclerosis. However, the role of pericardial fat in ventricular arrhythmia remains unclear.

METHODS AND RESULTS

Patients who had undergone dual-source computed tomography and 24-h Holter ECG were retrospectively enrolled. Quantification of the volume of pericardial fat surrounding the ventricles was analyzed using threshold attenuation of dual-source CT. The volume of pericardial fat was significantly different among those without ventricular premature beats (VPBs) in 24 h (n=28), those with occasional VPBs (n=54) and those with frequent VPBs (n=34) (12.5±6.1 cm(3)vs. 14±8.9 cm(3)vs. 29.9±17.3 cm(3), P<0.001). In addition, the number of VPBs strongly correlated with the volume of total pericardial fat (R=0.501, P<0.001), right ventricular (RV) pericardial fat (R=0.539, P<0.001), and left ventricular pericardial fat (R=0.376, P<0.001). Multivariate logistic regression analysis showed that quartiles of RV localized pericardial fat significantly increased the risk of frequent VPBs (OR=3.2, P=0.047). Moreover, the number of VPBs in 24 h was significantly different among the patients with a fat volume within the 25th percentile, 25-75th percentile and 75th percentile.

CONCLUSIONS

Pericardial fat (especially RV pericardial fat) was associated with the frequency of VPBs, which suggests the arrhythmogenic potential of ventricular pericardial fat. (Circ J 2016; 80: 1726-1733).

Beat-to-Beat Variability in Preload Unmasks Latent Risk of Torsade de Pointes in Anesthetized Chronic Atrioventricular Block Dogs

BACKGROUND

Beat-to-beat variability in ventricular repolarization (BVR) associates with increased arrhythmic risk. Proarrhythmic remodeling in the dog with chronic AV-block (CAVB) compromises repolarization reserve and associates with increased BVR, which further increases upon dofetilide infusion and correlates with Torsade de Pointes (TdP) arrhythmias. It was hypothesized that these pro-arrhythmia-associated increases in BVR are induced by beat-to-beat variability in preload.

METHODS AND RESULTS

Left ventricular monophasic action potential duration (LVMAPD) was recorded in acute (AAVB) and CAVB dogs, before and after dofetilide infusion. BVR was quantified as short-term variability of LVMAPD. The PQ-interval was controlled by pacing: either a constant or an alternating preload pattern was established, verified by PV-loop. The effect of the stretch-activated channel blocker, streptomycin, on BVR was evaluated in a second CAVB group. At alternating preload only, BVR was increased after proarrhythmic remodeling (0.45±0.14 ms AAVB vs. 2.2±1.1 ms CAVB, P<0.01). At CAVB, but not at AAVB, dofetilide induced significant proarrhythmia. Preload variability augmented the dofetilide-induced BVR increase at CAVB (+1.5±0.8 ms vs. +0.9±0.9 ms, P=0.058). In the second group, the increase in baseline BVR by alternating preload (0.3±0.03 ms to 1.0±0.8 ms, P<0.01) was abolished by streptomycin (0.5±0.2 ms, P<0.05).

CONCLUSIONS

In CAVB dogs, the inverse relation between BVR and repolarization reserve originates from an augmented sensitivity of ventricular repolarization to beat-to-beat preload changes. Stretch-activated channels appear to be involved in the mechanism of BVR. (Circ J 2016; 80: 1336-1345).