Dynamics of the QT interval in patients with exercise-induced ventricular tachycardia in normal and abnormal hearts

Gill, Jaswinder; Baszko, Artur; Xia, Ruiping; Ward, David

doi:10.1016/0002-8703(93)90534-g

Cited by 32 publications

(18 citation statements)

References 30 publications

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“…Interestingly, patients who did not undergo PTx continued to show different QTc dynamics. QTc dynamics could represent a risk factor for arrhythmias (34) that PTx is able to reverse.…”

Section: Discussionmentioning

confidence: 99%

Parathyroidectomy eliminates arrhythmic risk in primary hyperparathyroidism, as evaluated by exercise test

Pepe

Curione

Morelli

et al. 2013

European Journal of Endocrinology

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Objective: To investigate whether parathyroidectomy (PTx) reverses risk factors for arrhythmias related to the QT dynamic changes evaluated during bicycle ergometry exercise test (ET). Methods: Twenty-four postmenopausal women with primary hyperparathyroidism (PHPT) (mean age 60.0G8.4 years) and 30 sex-and age-matched controls underwent ET, echocardiography, and biochemical evaluation. The following stages were considered during ET: rest, peak exercise, and recovery. The patients were randomized to two groups: 12 underwent PTx (group A) and 12 were followed-up conservatively (group B). After 6 months, the patients were studied again. Results: Groups A and B showed no differences in mean baseline biochemical values, echocardiographic parameters, and QTc interval. PHPT patients showed an increased occurrence of ventricular premature beats (VPBs) during ET compared with controls (37.0 vs 6.6%, PZ0.03). Serum calcium level was a predictor of VPBs (PZ0.05). Mean value of QTc was in the normal range at baseline (group A: 401G16.9; group B: 402.25G13.5 ms) but significantly lower than controls (417.8G25.1 ms, P!0.01). A negative correlation was found between QTc and calcium values (PZ0.03). Physiological reduction of QTc interval from rest to peak exercise was not observed in PHPT patients before surgery. After PTx, group A had a significant reduction in VPBs compared with baseline (at baseline, 5 of 12 vs none of 12 patients after PTx, PZ0.03) and a restored normal QT adaptation during ET. Group B showed no significant changes after a 6-month period. Conclusions: PTx reduces the occurrence of VPBs and restored the QTc adaptation during ET.

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“…Interestingly, patients who did not undergo PTx continued to show different QTc dynamics. QTc dynamics could represent a risk factor for arrhythmias (34) that PTx is able to reverse.…”

Section: Discussionmentioning

confidence: 99%

Parathyroidectomy eliminates arrhythmic risk in primary hyperparathyroidism, as evaluated by exercise test

Pepe

Curione

Morelli

et al. 2013

European Journal of Endocrinology

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“…These mechanistic investigations on the time course of APD adaptation have also allowed providing a cellular and ionic basis to important clinical findings at the body-surface electrocardiogram, such as those suggesting QT-rate adaptation as a risk-stratification biomarker of arrhythmic mortality in patients with ischemic heart disease [22,51]. Indeed, the simulation study in [52] showed that: i) QT-rate adaptation in the electrocardiogram can be explained by APD adaptation at the cellular level; ii) the Na/K pump current is the main ionic determinant of APD and QT-rate adaptation; and iii) inhibition of the Na/K pump activity results in abnormalities in Na + and Ca 2+ homeostasis, which may increase arrhythmic risk through alterations in ERP, also leading to an increased likelihood of early-and delayed-afterdepolarizations [24,52,75].…”

Section: Multi-scale Studies Of Na/k Pump Regulation Of Cardiac Repolmentioning

confidence: 99%

Na/K pump regulation of cardiac repolarization: insights from a systems biology approach

Bueno‐Orovio

Sánchez

Pueyo

et al. 2013

Pflugers Arch - Eur J Physiol

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The sodium-potassium pump is widely recognized as the principal mechanism for active ion transport across the cellular membrane of cardiac tissue, being responsible for the creation and maintenance of the transarcolemmal sodium and potassium gradients, crucial for cardiac cell electrophysiology. Importantly, sodium-potassium pump activity is impaired in a number of major diseased conditions, including ischemia and heart failure. However, its subtle ways of action on cardiac electrophysiology, both directly through its electrogenic nature and indirectly via the regulation of cell homeostasis, make it hard to predict the electrophysiological consequences of reduced sodium-potassium pump activity in cardiac repolarization. In this review, we discuss how recent studies adopting the Systems Biology approach, through the integration of experimental and modeling methodologies, have identified the sodium-potassium pump as one of the most important ionic mechanisms in regulating key properties of cardiac repolarization and its rate-dependence, from subcellular to whole organ levels. These include the role of the pump in the biphasic modulation of cellular repolarization and refractoriness, the rate control of intracellular sodium and calcium dynamics and therefore of the adaptation of repolarization to changes in heart rate, as well as its importance in regulating pro-arrhythmic substrates through modulation of dispersion of repolarization and restitution. Theoretical findings are consistent across a variety of cell types and species including human, and widely in agreement with experimental findings. The novel insights and hypotheses on the role of the pump in cardiac electrophysiology obtained through this integrative approach could eventually lead to novel therapeutic and diagnostic strategies.

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“…Thus far, this association has not been reported. In other circumstances involving VT, a PQTc interval has been associated with the onset of malignant ventricular arrhythmia, 27 more frequent occurrence of life-threatening ventricular arrhythmia, 28,29 poor response to antiarrhythmic therapies in electrophysiologic study patients with ventricular arrhythmia, 30 and increased rates of death in such patients. 29 Numerous reports, however, are also found in the medical literature that have found no association with PQTc interval and the above VT issues.…”

Section: Limitations and Future Questionsmentioning

confidence: 99%

“…29 Numerous reports, however, are also found in the medical literature that have found no association with PQTc interval and the above VT issues. [31][32][33][34] The QTc interval may serve as yet another marker associated with poor outcome that the clinician may use in the evaluation of the out-of-hospital cardiac arrest patient.…”

Section: Limitations and Future Questionsmentioning

confidence: 99%

Prevalence, Therapeutic Response, and Outcome of Ventricular Tachycardia in the Out‐of‐hospital Setting: A Comparison of Monomorphic Ventricular Tachycardia, Polymorphic Ventricular Tachycardia, and Torsades de Pointes

Brady

DeBehnke²,

Laundrie

1999

Academic Emergency Medicine

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Abstract. Objective: To investigate out-of-hospital ventricular tachycardia (VT) cardiac arrest patients, comparing the prevalences and outcomes of the following VT subtypes among this population: monomorphic VT (MVT), polymorphic VT (PVT), and torsades de pointes (TdP, PVT with a prolonged QT interval). Methods: This was a retrospective review from a fire department-based paramedic system of nontraumatic VT cardiac arrest patients (January 1991 to December 1994) with a supraventricular perfusing rhythm (SVPR) at some time during out-ofhospital care, with a measurable QT interval. QT interval was measured from an SVPR, and corrected QT interval (QTc) was calculated and considered prolonged if > 0.45 sec. VT was classified as polymorphic or monomorphic. TdP was defined as PVT with a prolonged QT interval. Results: 196 patients were identified; six were excluded due to incomplete medical records, leaving 190 who met inclusion criteria and were used for data analysis. 117 (62%) patients had MVT, while 73 (38%) patients had PVT; of the 73 patients with PVT, 37 (51%) had normal QTc (non-TdP PVT) and 36 (49%) had prolonged QTc (TdP PVT). 97 (51%) patients had prolonged QTc (PQTc). Regardless of VT type (i.e., MVT vs PVT), 97 (51%) patients had prolonged QTc, with a mean QTc of 0.476 Ϯ 0.15 seconds prearrest and 0.464 Ϯ 12 seconds postarrest. Patients with PQTc were not more likely to have PVT (70 [37%] vs 76 [40%]; p = 0.705). No significant difference with respect to paramedic-witnessed arrests in each VT morphology group and each QT group was found. The overall hospital discharge rate was 28.4%. Regardless of VT type, patients had similar rates of out-of-hospital return of spontaneous circulation (ROSC) and hospital discharge; patients with PQTc were less likely to be discharged from the hospital (19.6% vs 37.6%; p = 0.01). 27.8% of TdP and 26.8% of non-TdP patients were discharged (p = 0.912). Conclusions: In this population of out-of-hospital VT arrest patients, MVT is the most common form of VT encountered; PVT and the subtype TdP are also seen in this population with approximately equal frequencies. All three rhythm types demonstrate similar responses to standard Advanced Cardiac Life Support therapy with equal rates of out-of-hospital ROSC and hospital discharge. PQTc may be a marker of poor clinical outcome in patients with out-of-hospital VT arrest. Key words: ventricular tachycardia; QT interval; polymorphic ventricular tachycardia; torsades de pointes; out-of-hospital; cardiac arrest. ACADEMIC EMERGENCY MEDICINE 1999; 6:609-617 S UDDEN cardiac death (SCD) represents a significant public health problem in the United States; ventricular tachycardia (VT) and ventricular fibrillation (VF) are frequently the car- 1,2 In many cases, VF is often preceded by VT; when classified from a morphologic perspective, VT is described as either monomorphic or polymorphic.2,3 Monomorphic VT (MVT) is frequently seen, easily diagnosed, and most often treated according to well-established guidelines in the out-of-hospital set...

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Dynamics of the QT interval in patients with exercise-induced ventricular tachycardia in normal and abnormal hearts

Cited by 32 publications

References 30 publications

Parathyroidectomy eliminates arrhythmic risk in primary hyperparathyroidism, as evaluated by exercise test

Parathyroidectomy eliminates arrhythmic risk in primary hyperparathyroidism, as evaluated by exercise test

Na/K pump regulation of cardiac repolarization: insights from a systems biology approach

Prevalence, Therapeutic Response, and Outcome of Ventricular Tachycardia in the Out‐of‐hospital Setting: A Comparison of Monomorphic Ventricular Tachycardia, Polymorphic Ventricular Tachycardia, and Torsades de Pointes

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