Changes in R-wave amplitude at implantation are associated with gender and orientation of insertable cardiac monitor: observations from the confirm Rx™ body posture and physical activity study.

BACKGROUND: Insertable cardiac monitors (ICMs) are small subcutaneously implanted devices that detect changes in R-wave amplitudes (RWAs), effective in arrhythmia-monitoring. Although ICMs have proven to be immensely successful, electrical artefacts are frequent and can lead to misdiagnosis. Thus, there is a growing need to sustain and increase efficacy in detection rates by gaining insight into various patient-specific factors such as body postures and activities. METHODS: RWAs were measured in 15 separate postures, including supine, lying on the right-side (RS) or left-side (LS) and sitting, and two separate ICM orientations, immediately after implantation of Confirm Rx™ ICM in 99 patients. RESULTS: The patients (53 females and 46 males, mean ages 66.62 ± 14.7 and 66.40 ± 12.25 years, respectively) had attenuated RWAs in RS, LS and sitting by ~ 26.4%, ~ 27.8% and ~ 21.2% respectively, compared to supine. Gender-based analysis indicated RWAs in RS (0.32 mV (0.09-1.03 mV), p < 0.0001) and LS (0.37 mV (0.11-1.03 mV), p = 0.004) to be significantly attenuated compared to supine (0.52 mV (0.20-1.03 mV) for female participants. Similar attenuation was not evident for male participants. Further, parasternally oriented ICMs (n = 44), attenuated RWAs in RS (0.37 mV(0.09-1.03 mV), p = 0.05) and LS (0.34 mV (0.11-1.03 mV), p = 0.02) compared to supine (0.48 mV (0.09-1.03 mV). Similar differences were not observed in participants with ICMs in the 45°-relative-to-sternum (n = 46) orientation. When assessing the combined effect of gender and ICM orientation, female participants demonstrated plausible attenuation in RWAs for RS and LS postures compared to supine, an effect not observed in male participants. CONCLUSION: This is the first known study depicting the effects on RWA due to body postures and activities immediately post-implantation with an overt impact by gender and orientation of ICM. Future work assessing the cause of gender-based differences in RWAs may be critical. TRIAL REGISTRATION: Clinical Trials, NCT03803969. Registered 15 January 2019 - Retrospectively registered, https://clinicaltrials.gov/NCT03803969.

R-wave amplitude changes with posture and physical activity over time in an insertable cardiac monitor.

Background: Insertable cardiac monitors (ICMs) are accepted tools in cardiac arrhythmia management. Consistent R-wave amplitude (RWA) is essential for optimal detection. Objectives: Assess RWAs with posture/activities at insertion and at 30 days. Methods: Participants (n = 90) with Confirm Rx™ ICM had RWAs measured in different postures (supine, right-side [RS], left-side [LS], sitting, and standing) and defined physical activities (including isometric push [IPUSH] and pull) at 2 time points. ICMs were inserted in 45° to sternum and parasternal orientations. Results: There were significant reductions at insertion with RS, LS, sitting, or standing vs supine (reference position) (all P < .05). At 30 days, significant changes only occurred with LS and sitting (P < .05). Sex had an effect on RWAs, with females having significant variability at insertion (supine vs RS, LS, sitting, standing, and IPUSH; all P < .05). Males showed large RWA interpatient variabilities but minimal differences between positions vs supine. At 30 days, RS, LS, and sitting positions remained significant for females (P < .05), while in males RWAs were higher than at insertion for most postures and activities. The orientation 45° to sternum had consistently higher RWAs vs parasternal orientation at both time points (P < .0001). In females, ICM orientation had no significant effect on RWAs; however, in males the 45° to sternum produced higher RWAs. ICM movement from the insertion site showed no correlation with RWA changes. Conclusion: The mean RWAs were higher at 30 days with less interparticipant and interpostural variability; males had higher RWAs compared to females; 45° to sternum orientation had higher RWAs; and ICM migration from the insertion site did not affect RWAs.

Clinical and coronary haemodynamic determinants of recurrent chest pain in patients without obstructive coronary artery disease - A pilot study.

BACKGROUND: Coronary haemodynamic testing frequently identifies abnormal pathophysiological parameters in patients with angina and non-obstructed coronaries on angiography (NoCAD) but the clinical utility of these measures has received limited attention. OBJECTIVE: This study aims to identify the clinical and coronary haemodynamic determinants of recurrent chest pain at one month in patients with NoCAD. METHODS: Patients with angina, NoCAD (<50% stenosis) and normal LV systolic function underwent invasive coronary haemodynamic testing involving: (1) angiographic TIMI frame and opacification rate, (2) microvascular functional measures including coronary flow reserve (CFR) and hyperaemic microvascular resistance (HMR), (3) coronary endothelial function assessment with low dose intracoronary acetylcholine (IC-ACh) infusions (0.18 µg/min & 1.8 µg/min over 2 min), and (4) Provocative spasm testing with high dose IC-ACh boluses (25, 50 and 100 µg). Clinical and health status were assessed at baseline and one month. RESULTS: In the 49 NoCAD patients (78% female, mean age of 54 ±â€¯11) undergoing comprehensive coronary haemodynamic testing, 33 (67%) continued to experience chest pain at one month. Determinants of recurrent chest pain on univariate analysis included baseline chest pain status or a HMR > 1.9. Multivariate logistic regression analysis identified frequent angina at baseline (OR: 68.9 [4.1, 1165.0], p = 0.003), previous unstable angina admission (OR: 43.9 [3.5, 547.9], p = 0.003) and a HMR > 1.9 (OR: 15.6 [2.1, 114.0], p = 0.007) as independent predictors of recurrent chest pain. CONCLUSION: In this small pilot study, an abnormal HMR was the only coronary haemodynamic parameter that was a determinant of ongoing angina at short-term follow-up.

Cardiac hemodynamics in men versus women during acute ST-segment elevation myocardial infarction.

Several biologic and clinical factors contribute to the increased 30-day mortality and re-infarction rate in women with ST-segment elevation myocardial infarction (STEMI). Sex differences in cardiac hemodynamic parameters such as pulmonary capillary wedge pressure (PCWP) have not been examined and might play an important role. The objectives of the present study were to examine whether female sex is an independent determinant of PCWP during acute STEMI and whether an elevated PCWP contributes to all-cause 30-day mortality and re-infarction in women. The clinical, angiographic, and hemodynamic features of 470 consecutive patients with STEMI (n = 135 women) undergoing emergency coronary angiography with right-side heart catheterization were evaluated with respect to sex. Women had an elevated PCWP (20 ± 8 vs 16 ± 7 mm Hg, p <0.001) and reduced mixed venous oxygen saturation (67 ± 11% vs 71 ± 9%, p = 0.004). On multivariate analysis, female sex (ß = 4.04, 95% confidence interval [CI] 2.04 to 6.04, p <0.001), hypertension (ß = 2.07, 95% CI 0.31 to 3.83, p = 0.021), and creatine kinase-estimated infarct size (ß = 0.001, 95% CI 0.001 to 0.002, p ≤0.001) were independent predictors of an elevated PCWP. Female sex exerted a minor independent effect on 30-day mortality and re-infarction (odds ratio 2.36, 95% CI 1.25 to 4.46, p = 0.008). However, once PCWP was entered into the mediation model, sex was no longer significant, suggesting that the effect of sex on the post-STEMI outcomes is potentially mediated through PCWP (odds ratio 1.07, 95% CI 1.02 to 1.12, p = 0.011). In conclusion, during acute STEMI, women have greater left ventricular filling pressures compared with men, independent of age, hypertension, and infarct size. The biologic explanation for this difference requires additional investigation, although it does not appear to contribute to the increased 30-day mortality and re-infarction rate observed in women.

Evaluation of gender differences in Door-to-Balloon time in ST-elevation myocardial infarction.

BACKGROUND: A delayed Door-to-Balloon (DTB) time in women with ST-elevation myocardial infarction (STEMI) has been associated with an increased mortality. The objectives of this study were to (a) quantify the components of the delayed DTB time in women and (b) assess the independent effect of gender on DTB time in patients undergoing percutaneous coronary intervention (PCI) for STEMI. METHODS: Clinical parameters were prospectively collected for 735 STEMI patients undergoing primary PCI from 2006 to 2010, with particular attention to the components of DTB time, including the onset of chest pain and the 'code' notification of the STEMI team by the Emergency Department. RESULTS: Women were significantly older with more co-morbidity. Upon hospital arrival they also experienced delays in Door-to-Code (23 vs. 17 min, P=.012), Code-to-Balloon (63 vs. 57 min, P=.001) and thus DTB time (88 vs. 72 min, P=.001). After multivariate adjustment, independent determinants of DTB time included female gender (ratio of geometric means [RGM]=1.13; 95% CI 1.02-1.26; P=.022), hypertension (RGM=1.12, 95% CI 1.02-1.23, P=.014), maximum ST-elevation (RGM=0.97, 95% CI 0.94-0.98, P<.001), office hours (RGM=0.84, 95% CI 0.78-0.92, P<.001) and triage category (RGM=1.23, 95% CI 1.09-1.40, P=.001). CONCLUSIONS: Women experience delays in identification of the STEMI diagnosis and also in the PCI process. Thus a multifaceted approach addressing both the diagnosis and management of STEMI in women is required.

Chest pain in patients with 'normal angiography': could it be cardiac?

Approximately 20% of patients undergoing diagnostic angiography for the evaluation of chest pain are found to have a normal coronary angiogram. Although this finding is generally associated with a low risk of cardiac events, approximately half will continue to experience chest pain over the next 12 months. Therefore, the finding of normal angiography warrants further evaluation of the potential causes for the presenting chest pain if we are to improve the disability suffered by these patients. In this review, the potential non-cardiac and cardiac causes for the chest pain in patients with normal angiography are briefly discussed with an in-depth focus on coronary vasomotor disorders including coronary artery spasm (variant angina) and microvascular disorders such as syndrome X, microvascular angina, the coronary slow flow phenomenon and microvascular spasm.