Postoperative real-time electrocardiography monitoring detects myocardial ischemia: a case report
This case report outlines the utility and challenges of remote continuous postoperative electrocardiography ECG) monitoring, which is routed through a secure smartphone to provide real-time detection and management of myocardial ischemia.
A 42-yr-old male with previous myocardial infarction and angioplasty underwent a radical prostatectomy. At three hours and 45 min postoperatively, remote real-time ECG monitoring was initiated upon the patient’s arrival on a regular surgical ward. Monitor alerts were routed to a study clinician’s smartphone. About six hours postoperatively, alarms were received and horizontal ST segment depressions were observed. A 12-lead ECG validated the ST segment changes, prompting initiation of a metoprolol iv and a red blood cell transfusion. Approximately seven hours and 30 min postoperatively, the ST segments normalized. The patient was discharged on postoperative day 3 and followed for four years without any sequelae.
This case report illustrates the use of remote ECG monitoring and clinician response in real time with the use of a smartphone. With each alert, a small ECG strip is transmitted to the smartphone for viewing. In our view, this technology and management system provides a possible means to interrupt myocardial ischemic cascades in real time and prevent postoperative myocardial infarction.
KeywordsFalse Alarm Metoprolol Desflurane Prose Signal Quality Index
Le monitorage électrocardiographique postopératoire en temps réel pour détecter l’ischémie myocardique: une présentation de cas
Cette présentation de cas décrit l’utilité et les défis d’un monitorage électrocardiographique (ECG) postopératoire continu à distance, dont le signal est acheminé via un téléphone intelligent sécurisé pour permettre la détection et la prise en charge en temps réel de l’ischémie myocardique.
Un homme de 42 ans présentant des antécédents d’infarctus du myocarde et d’angioplastie a subi une prostatectomie radicale. Trois heures et 45 minutes après l’opération, un monitorage ECG en temps réel a été lancé à distance, soit à l’arrivée du patient dans un service régulier de chirurgie. Les alertes du moniteur ont été acheminées vers le téléphone intelligent d’un clinicien de l’étude. Après environ six heures postopératoires, des signaux ont été reçus et des sous-décalages horizontaux du segment ST observés. Un ECG à 12 dérivations a permis de valider les changements au segment ST, incitant l’amorce d’une iv de métoprolol et une transfusion d’érythrocytes. Approximativement sept heures et 30 minutes après l’opération, les segments ST se sont normalisés. Le patient a reçu son congé au 3ème jour postopératoire, puis il a été suivi pendant quatre ans sans séquelles.
Cette présentation de cas illustre l’utilisation d’un monitorage ECG à distance et la réponse du clinicien en temps réel à l’aide de son téléphone intelligent. Lors de chaque alerte, une petite bande de rythme ECG est transmise au téléphone intelligent pour être visionnée. Selon nous, cette technologie et ce système de gestion offrent une possibilité d’interrompre les cascades d’ischémie myocardique en temps réel et de prévenir l’infarctus du myocarde postopératoire.
This case report illustrates the use of remote continuous postoperative electrocardiography (ECG) monitoring, which is routed through a smartphone to provide detection and initiate clinical management of myocardial ischemia. It was part of a feasibility observational trial, PROSE 3 (Clinicaltrials.gov NCT01423136), in which 89 patients were enrolled and 69 completed the study. Electrocardiogram ST segment analysis during Holter monitoring has been studied prior to, during, and after surgery,1-3 but only the postoperative ST segment changes were associated with postoperative ischemic cardiac events in a multivariate analysis model.2 Postoperative myocardial ischemia can be treated by decreasing heart rate reductions, thereby interfering with the myocardial ischemic cascade.4,5 Nevertheless, as postoperative ECG analysis is typically performed offline, days after the associated myocardial ischemic event, timely treatment is not possible. To address this shortcoming, PROSE 3 was conducted to examine the feasibility of real-time ST segment analysis as demonstrated with this case.
This case shows how technology can link clinicians to a changing clinical situation in real-time, enabling provision of appropriate and timely medical care. Technology helped to alert the perioperative team so that a potentially serious cardiac ischemic event could be appropriately interrupted. Importantly, during the ischemic event, the patient did not experience any untoward symptoms, and standard patient care on the surgical ward was insufficient to identify the evolving cardiac event. Such real-time ECG monitoring differs from previous efforts using Holter monitoring which provides information that is time delayed by hours or days. The remote monitoring, as described, also differs from traditional telemetry, which is available only in specialized locations, such as step-down, intensive care, or cardiac care units. Moreover, the integration of telemetry into these sites requires extensive nursing training and continuing education.
Indeed, telemetry monitoring for ST segment changes has been used after acute coronary syndromes and coronary artery interventions,7 but it remains an underutilized technology even in these circumstances.8 Postoperative ST segment monitoring via telemetry after non-cardiac surgery is even rarer, and its availability on surgical wards is unknown.7 While remote ECG monitoring technology has existed for some time, there is a lack of literature concerning its use for remote real-time off-site monitoring or on regular surgical wards during the postoperative period. Nevertheless, some studies have been published concerning its use in the intensive care unit,9-13 including during weaning from mechanical ventilation.14-17 Importantly, none of those studies involved remote off-site monitoring.
An important consideration for remote patient monitoring is ensuring that the technology provides the appropriate documentation, privacy, and firewall protection befitting a medical recording and transmission system. Our system has de-identified encrypted e-mail transmissions, e-mails stored behind the firewall, full disclosure behind the firewall, and “double-lock” data storage as per Research Ethics Board requirements. One of the drawbacks of remote cardiac monitoring is the relatively large number of false alarms, and this continues to be a challenge with this emerging technology. During the 24 hr of monitoring with the patient described in this report, there were 60 false alarms and three true alarms. Causes for false alarms include motion artifacts, electrolyte shifts, temperature changes, and tachycardia.18 In addition, there are biomedical engineering reasons for false alarm triggers, and work in progress on signal quality index and signal-to-noise ratio has shown improvements in alarm algorithms.19-21
Postoperative myocardial infarction is one of the most frequent and serious adverse events.22 In a study of vascular patients, the overall mortality was 3.4%, and seven of eight deaths were related to perioperative myocardial ischemic injury (PMII). Of 236 patients, PMII occurred in 42 (17.8%) patients: 22 myocardial infarctions, 11 congestive heart failures, and 12 new arrhythmias (three patients had two PMII events). The mean hospital length of stay was 16.8 and 10.0 days for patients with and without PMII, respectively (P < 0.001).23 In a study of patients ≥ 60 yr of age, 129/1,422 (9.1%) developed at least one major adverse cardiac event, and cardiac death occurred in 11 patients (0.8%).24
With the patient described in the present report, the combination of perioperative blood loss, a missed evening metoprolol dose, and tachycardia undoubtedly contributed to the evolving cardiac ischemic cascade. The synergistic combination of missing postoperative beta-blocker doses and bleeding on myocardial ischemia has been previously described.25 The rebound effect of increased heart rate and contractility after missing a beta-blocker dose in the postoperative period, combined with postoperative anemia, is likely a factor leading to an imbalance of myocardial oxygen supply and demand and the resulting ischemia. An acute coronary syndrome may be the result of plaque rupture (type 1) or an imbalance of supply and demand (type 2),22 and the ensuing ischemic cascade26 may be interrupted by early intervention. In this case, the troponin I rose to only 0.05 µg·L−1 and no new ECG changes persisted, so it is unlikely that the patient experienced a postoperative myocardial infarction. In view of the specificity of postoperative myocardial ischemia in predicting myocardial ischemic complications, we assume that the early intervention to interrupt the ischemic cascade prevented a likely postoperative myocardial infarct.2,10
In conclusion, this case report illustrates the usefulness of real-time remote monitoring of ECG signals recorded from hospitalized patients at risk of cardiac events. This case involved a postoperative surgical patient who experienced electrocardiographic evidence of myocardial ischemia during his recovery on a standard surgical floor. The patient was otherwise asymptomatic. The ECG monitoring, as described, allowed for timely detection and appropriate clinical intervention, otherwise that would not have occurred. Real-time remote ECG monitoring during the postoperative period is a potentially useful tool to help prevent perioperative myocardial infarction.
This observational trial was funded by The Ottawa Hospital Academic Medical Organization as part of the initiative of the Ontario Ministry of Health Alternative Funding Plan/Innovation Fund Provincial Oversight Committee. We would also like to state that there was no financial conflict of interest in this project. We express our appreciation to Spacelabs for their invaluable advice regarding this project.
Conflicts of interest
This submission was handled by Dr. Steven Backman, Associate Editor, Canadian Journal of Anesthesia.
Homer Yang was the principal author and principal investigator of the PROSE 3 project. Alan Chaput, Ashraf Fayad, and Stuart Oake were co-authors. Alan Chaput and Ashraf Fayad were co-investigators of PROSE 3. Alan Chaput contributed substantially to the initial PROSE 3 protocol and to writing the case report. Ashraf Fayad contributed substantially to the conception and design of PROSE 3. Ashraf Fayad and Stuart Oake contributed substantially to writing the manuscript. Stuart Oake contributed substantially to the design of the manuscript. Mary Lou Crossan was the research assistant. She contributed to patient recruitment, study conduct, and data acquisition for PROSE 3, all of which led to this case report.
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