ER resulting from HIRT appears to have a benign course compared with rhabdomyolysis of other aetiologies in patients with a serum CK greater than 25 000 units/L. Conservative management of ER appears to be adequate, although this requires confirmation in future prospective studies.
Background
Ticagrelor is an oral anti-platelet agent that is a reversible and direct inhibitor of the adenosine diphosphate P2Y12 receptor. Ticagrelor’s brady-arrhythmic potential was investigated in a sub-study of the PLATO trial, which concluded that the effects were transient and not clinically significant beyond the acute initiation phase. Since then, there have been emerging reports of ticagrelor-associated high-degree heart block, requiring drug discontinuation and pacemaker insertion. We present a case of symptomatic ventricular pauses in a patient loaded with ticagrelor post-percutaneous coronary intervention (PCI) for non-ST elevation acute coronary syndrome (NSTEACS) and review the literature relating to ticagrelor and its brady-arrhythmic potential.
Case summary
A 59-year-old female presented to our hospital with NSTEACS and received an oral load of ticagrelor 180 mg following PCI to her mid-left circumflex coronary artery. Three hours after, four pauses were observed on telemetry over a 20 min period, the longest being 18.5 s in duration. Ticagrelor was ceased and clopidogrel commenced in place. No arrhythmic events were recorded on loop recorder interrogation following ticagrelor discontinuation.
Discussion
The exact mechanism of ticagrelor-induced brady-arrhythmia is unclear, although inhibition of adenosine reuptake is proposed as likely due to structural similarities between ticagrelor and adenosine. In the setting of acute coronary syndrome treated with ticagrelor, extracellular adenosine concentrations are amplified by the ischaemic milieu with myocardial adenosine release and blunted cellular reuptake. This leads to enhanced agonism of adenosine A1 receptors, causing negative chronotropy and dromotropy. This case report highlights ticagrelor’s brady-arrhythmic potential even in the absence of baseline conduction disease or concurrent confounding medications.
Objective: We sought to assess the different CT aortic root measurements and determine their relationship to transthoracic echocardiography (TTE). Methods: TTE and ECG-gated CT images were reviewed from 70 consecutive patients (mean age 54 ± 18 years; 67% male) with tricuspid aortic roots (trileaflet aortic valves) between Nov 2009 and Dec 2013. Three CT planes (coronal, short axis en face and three-chamber) were used for measurement of nine linear dimensions. TTE aortic root dimension was measured as per guidelines from the parasternal long axis view. Results: All CT short axis measurements of the aortic root had excellent reproducibility (intraclass correlation coefficient, ICC 0.96–0.99), while coronal and three-chamber planes had lower reproducibility with ICC 0.90 (95% CI 0.84–0.94) and ICC 0.92 (0.87–0.95) respectively. CT coronal and short axis maximal dimensions were systematically larger than TTE (mean 2 mm larger, p < 0.001), while CT cusp to commissure measurements were systematically smaller (CT RCC-comm mean 2 mm smaller than TTE, p < 0.001). All CT short axis measurements had excellent correlation with aortic root area with CT short axis maximal dimension marginally better than the rest (Pearson’s R 0.97). Conclusion: Systematic differences exist between CT and TTE dependent on the CT plane of measurement. All CT short axis measurements of the aortic root had excellent reproducibility and correlation with aortic root area with maximal dimension appearing marginally better than the rest. Our findings highlight the importance of specifying the chosen plane of aortic root measurement on CT. Advances in knowledge: Systematic differences in aortic root dimension exist between TTE and the various CT measurement planes. CT coronal and short axis maximal dimensions were systematically larger than TTE, while CT cusp to commissure measurements were smaller. CT readers should indicate the plane of measurement and the specific linear dimension to avoid ambiguity in follow-up and comparison.
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