Ryan E. Wilson

A case of caffeine-induced coronary artery vasospasm of a 17-year-old male.

The intentional consumption and use of stimulants, such as caffeine, are known to have numerous interactions with the human cardiovascular system. Ex vivo studies have shown caffeine-induced vasoconstriction of coronary arteries (Forman et al. in Ann Emerg Med 29:178–180, 1997). We report on a case of a 17-year-old male who presented with angina and an abnormal electrocardiogram (ECG) concerning for ST elevation myocardial infarct. He was found to have diffuse ECG changes and markedly elevated cardiac enzymes. A transthoracic echocardiogram revealed a reduced left ventricular (LV) systolic function as well as segmental wall motion abnormalities consistent with an ischemic insult. The patient admitted to consuming near lethal doses of caffeine immediately preceding his angina. He was diagnosed with coronary vasospasms as a result of stimulant use. During hospitalization, ECG changes resolved, cardiac enzymes started trending downward, and LV systolic function returned to normal, all consistent with stunned myocardium that fully recovered. This case strongly suggests that overuse of stimulants, such as caffeine, should be considered in patients presenting with coronary vasospasms, particularly in teenagers and young adults.

A head-to-head pharmacodynamic comparison of prasugrel vs. ticagrelor after switching from clopidogrel in patients with coronary artery disease: results of a prospective randomized study

AIMS Pharmacodynamic (PD) studies comparing prasugrel and ticagrelor have reached inconsistent findings. Therefore, a comprehensive investigation comparing the PD effects of prasugrel vs. ticagrelor after switching from clopidogrel therapy, exploring both loading dose (LD) and maintenance dose (MD) regimens represented the aim of this study. METHODS AND RESULTS Patients (n = 110) with coronary artery disease were randomized to prasugrel (60 mg LD/10 mg MD q.d.) or ticagrelor (180 mg LD/90 mg MD b.i.d) therapy for 1 week. Pharmacodynamic assessments were conducted using three assays (vasodilator-stimulated phosphoprotein, VerifyNow P2Y12, and light transmittance aggregometry, LTA) at baseline, 30 min, 2, 24 h, and 1 week. The impact of initiating ticagrelor MD 12 vs. 24 h after LD administration was also assessed. Switching clopidogrel-treated patients to an LD of prasugrel or ticagrelor was associated with a reduction in platelet reactivity at 30 min and was sustained at all time points up to 1 week with the MD (P < 0.001 for all assays). Platelet reactivity was similar with prasugrel and ticagrelor with all assays at 30 min, 2 h, and 1 week (P > 0.05 for all time points), with the exception of LTA at 30 min (lower with prasugrel; P = 0.003). At 24 h, platelet reactivity was lower among patients initiating ticagrelor MD after 12 vs. 24 h post-LD. Rates of high platelet reactivity (HPR) were markedly reduced and similar between groups. CONCLUSION Prasugrel and ticagrelor exert similar levels of P2Y12 inhibition achieving more potent PD effects and reduced HPR rates compared with clopidogrel which are reached promptly following LD and sustained with MD. CLINICALTRIALSGOV IDENTIFIER NCT01852175.

Impact of aspirin dose on adenosine diphosphate-mediated platelet activities. Results of an in vitro pilot investigation.

Different aspirin dosing regimens have been suggested to impact outcomes when used in combination with adenosine diphosphate (ADP) P2Y12 receptor antagonists. Prior investigations have shown that not only aspirin, but also potent ADP P2Y12 receptor blockade can inhibit thromboxane A2-mediated platelet activation. The impact of aspirin dosing on ADP mediated platelet activities is unknown and represents the aim of this in vitro pilot pharmacodynamic (PD) investigation. Twenty-six patients with stable coronary artery disease on aspirin 81 mg/day and P2Y12 naïve were enrolled. PD assessments were performed at baseline, while patients were on 81 mg/day aspirin and after switching to 325 mg/day for 7 ± 2 days with and without escalating concentrations (vehicle, 1, 3, and 10 μM) of prasugrels active metabolite (P-AM). PD assays included flow cytometric assessment of VASP to define the platelet reactivity index (PRI) and the Multiplate Analyzer (MEA) using multiple agonists [ADP, ADP + prostaglandin (PGE1), arachidonic acid (AA), and collagen]. Escalating P-AM concentrations showed incremental platelet P2Y12 inhibition measured by VASP-PRI (p<0.001). However, there were no differences according to aspirin dosing regimen at any P-AM concentration (vehicle: p=0.899; 1 μM: p=0.888; 3 μM: p=0.524; 10 μM: p=0.548). Similar findings were observed in purinergic markers assessed by MEA (ADP and ADP+PGE1). P-AM addition significantly reduced AA and collagen induced platelet aggregation (p<0.001 for all measures), irrespective of aspirin dose. In conclusion, aspirin dosing does not appear to affect PD measures of ADP-mediated platelet reactivity irrespective of the degree of P2Y12 receptor blockade. P2Y12 receptor blockade modulates platelet reactivity mediated by alternative activators.

An algorithm for identification of ST-elevation myocardial infarction patients by emergency medicine services

OBJECTIVE ST-elevation myocardial infarction (STEMI) identification by emergency medicine services (EMS) leading to pre-hospital catheterization laboratory (CL) activation shortens ischemic time and improves outcomes. We examined the incremental value of addition of a screening clinical tool (CT), containing clinical information and a Zoll electrocardiogram (ECG)-resident STEMI identification program (ZI) to ZI alone. METHODS All EMS-performed and ZI-analyzed ECGs transmitted to a percutaneous coronary intervention hospital from October 2009 to January 2011 were reviewed for diagnostic accuracy. ZI performance was also compared to ECG interpretations by 2 experienced readers The CT was then retrospectively applied to determine the incremental benefit above the ZI alone. RESULTS ST-elevation myocardial infarction was confirmed in 23 (7.5%) of 305 patients. ZI was positive in 37 (12.1%): sensitivity: 95.6% and specificity: 94.6%, positive predictive value (PPV), 59.5%, negative predictive value (NPV), 99.6%, and accuracy of 93.8%. Moderate agreement was observed among the readers and ZI. CT criteria for CL activation were met in 24 (7.8%): 20 (83.3%) were confirmed STEMIs: sensitivity: 86.9%, specificity: 98.5%, a PPV: 83.3%, and NPV: 98.6%, accuracy of 97.7%. CT + ZI increased PPV (P<0.05) and specificity (P<0.003) by reducing false positive STEMI identifications from 15 (4.9%) to 4 (1.3%). CONCLUSIONS In an urban cohort of all EMS transmitted ECGs, ZI has high sensitivity and specificity for STEMI identification. Whereas the PPV was low, reflecting both low STEMI prevalence and presence of STEMI-mimics, the NPV was very high. These findings suggest that a simplified CT combined with computer STEMI interpretation can identify patients for pre-hospital CL activation. Confirmation of these results could improve the design of STEMI care systems.

PHARMACODYNAMIC EFFECTS OF SKIPPING TICAGRELOR MAINTENANCE DOSING FOLLOWING LOADING DOSE ADMINISTRATION

methods: Patients (n=27) on maintenance aspirin (81 mg/qd) and clopidogrel (75 mg/qd) were prospectively enrolled in a two phase study. In phase 1, patients received a morning 180 mg ticagrelor LD, but not the evening 90 mg MD. After a 15-day wash-out period (patients resumed clopidogrel), phase 2 was performed in which the morning 180 mg ticagrelor LD was followed by the evening 90 mg MD. PD assessments (VerifyNow, LTA and VASP) were performed at baseline, and 2 and 24 hrs after LD.

PHARMACODYNAMIC EFFECTS OF EV–077 IN PATIENTS WITH DIABETES MELLITUS ON CLOPIDOGREL MONOTHERAPY: RESULTS OF AN IN VITRO PILOT INVESTIGATION

Diabetes mellitus (DM) patients have increased thromboxane A2 (TXA2) which activate TX prostanoid receptors (TPR). In DM patients, EV–077, a combined TXA2 synthase inhibitor and TPR antagonist, achieves more effective platelet inhibition compared with aspirin. However, the effects of EV–077 in