Transtelephonic electrocardiography in the management of patients with acute coronary syndrome

UNCORRECTED PROOF 1Transtelephonic electrocardiography in the management of patients 2with acute coronary syndrome ☆ 3GyorgyQ1 Papai, MD, a Ildiko Racz, MD, b Daniel Czuriga, MD, PhD, b, ⁎Gyorgy Szabo, MD, c 4Istvan Ferenc Edes, MD, PhD, c Istvan Edes, MD, DSc b 5 a Hungarian National Ambulance Service 6 b Institute of Cardiology, University of Debrecen, Medical and Health Science Center, Debrecen, Hungary 7 c Heart and Vascular Center, Semmelweis University, Budapest, Hungary 8 9Abstract10 Background, purpose: The efficacy of the transtelephonic ECG system (TTECG) in the 11 management of ST segment elevation myocardial infarction (STEMI) was examined with regard 12 to the ambulance serviceand percutaneous coronary intervention (PCI)-related delay times, the 13 prehospital medical therapy and the in-hospital mortality rate. 14 Methods: The study was conducted as a collaborative effort between the University of Debrecen and 15 the Hungarian National Ambulance Service. Altogether 397 patients were recruited in the TTECG 16 group, while 378 patients transported to the PCI centre without TTECG served as controls. 17 Results: More accurate prehospital medical therapy was achieved in the TTECG group. The PCI18 related delay times were significantly shorter, while the in-hospital mortality rate was significantly 19 lower in the TTECG group than among the controls. 20 Conclusions: The findings illustrate that TTECG is a valuable tool which may potentially improve 21 the regional management of STEMI patients. 22 © 2014 Published by Elsevier Inc. 23 24 Keywords: Transtelephonic ECG; Acute coronary syndrome; STEMI; Emergency medical services 25 26 Introduction 27 Recent guidelines [1] state that the timely diagnosis of 28 acute coronary syndrome (ACS) is the key to successful 29 management. This is especially true for patients with ST 30 segment elevation myocardial infarction (STEMI). In cardiac 31 emergency situations, an early diagnosis and the prevention 32 of delay are critical as concerns the outcome. The very early 33 phase of STEMI is the most critical time, during which the 34 patient is liable to suffer a cardiac arrest and other 35 complications. Moreover, the earlier the treatment (reperfu36 sion therapy) is commenced, the greater the beneficial effect 37 (“time is muscle”). 38 The prehospital primary diagnosis of STEMI is usually 39 based on the medical history, the physical examination and 40 especially the electrocardiogram (ECG) [2], as biochemical 41 cardiac marker measurements are not readily available in 42most cases. Consequently, the correct interpretation of ECGs 43in cardiac emergency patients with chest pain is of utmost 44importance as the cornerstone of the diagnosis. On the other 45hand, cardiac emergencies may occur far from specialist 46hospitals (this is especially true in Hungary), and staff at 47many healthcare services, emergency services, geriatric 48centres, or general and private practices are not sufficiently 49expert or not qualified to interpret ECGs in detail. 50One approach to overcome this problem is the use of the 51transtelephonic ECG (TTECG). This usually involves the 52direct transmission of a locally recorded conventional ECG 53by telephone, which is decoded to a standard ECG on a 54computer in a cardiac centre [3], where everything is 55available for an immediate professional ECG evaluation and 56interpretation. The usefulness of different TTECG and ECG 57monitoring systems has already been established in the 58diagnosis and follow-up of various forms of ischemic heart 59disease [4–7], in the management of out-of-hospital chest 60pain emergencies [8,9] and for the detection of atrial 61fibrillation and other arrhythmias in different clinical 62situations [10–12]. 63In 2008, a pilot developmental project was initiated in the 64north-eastern region of Hungary (about 1.5 million people), Available online at www.sciencedirect.com ScienceDirect Journal of Electrocardiology xx (2014) xxx–xxx www.jecgonline.com ☆ Conflicts of interest: The authors have no conflict of interest to disclose. ⁎Corresponding author at: University of Debrecen, Medical and Health Science Center, Institute of Cardiology, Móricz Zs. krt. 22, H-4032 Debrecen, Hungary. E-mail address: [email protected] 0022-0736/$ –see front matter © 2014 Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jelectrocard.2014.02.007 YJELC-51830; No of Pages 6 UNCORRECTED PROOF 65 in which the Hungarian National Ambulance Service was 66 uniformly equipped with a TTECG system which is 67 extensively used in all cardiac emergencies. A 24-hour 68 service network was established between the ambulance 69 service units and the regional cardiac centre (the Institute of 70 Cardiology at the University of Debrecen) and the locally 71 registered ECGs are immediately transmitted by phone to 72 the centre. 73 The aim of the present study is to examine the efficacy of 74 the TTECG system, in combination with consultation with 75 the cardiologist, in the diagnosis and management of patients 76 with acute chest pain, with special focus on STEMI. 77 Consideration is given to the ambulance service contact 78 and transport times, the percutaneous coronary intervention 79 (PCI)-related delay times (door to sheath insertion and door 80 to balloon times), the prehospital medical therapy and the in81 hospital mortality rate. 82 Methods 83 The study was conducted between January 1, 2009 and 84 December 31, 2010 in the north-eastern region of Hungary as 85 a collaborative effort between the Institute of Cardiology in 86 Debrecen and the Hungarian National Ambulance Service. A 87 total of 48 ambulance units provided emergency services 88 throughout the region to a population of approximately 89 1500000 residents. 90 All units had been uniformly equipped with both 91 conventional ECG and battery-operated 12 lead, portable 92 TTECG system (HeartView P12/8 Plus, Aerotel Medical 93 Systems). The conventional ECG machine recorded 12 leads 94 in 4 consecutive steps (3 leads simultaneously) at a standard 95 paper speed (25 mm/sec) and voltage setting (10 mm/mV). 96 The HeartView P12/8 Plus device was supplemented with 3 97 external, cable-connected electrodes, which were placed on 98 the left and right arms and on the left side of the waist. In 99 addition, 4 embedded electrodes were located on the back of 100 the main unit. This arrangement of electrodes allows the 101 recording of both the limb and precordial leads, by placing 102 the main unit in 3 different positions on the chest. A 103 2.5 second interval of each lead and a 10 second interval of 104 the rhythm strip (lead II) were recorded with a sampling rate 105 of 375 samples/second (least significant bit voltage resolu106 tion of 39 μV), resulting in a standard 12 lead ECG layout 107 with every lead separated by 1 mV calibration signals. The 108 electrode positions for the conventional ECG machine and 109 the TTECG system were similar. 110 The ambulance units were staffed with either a doctor or a 111 primary-care paramedic trained for emergency cardiac 112 service and advanced cardiovascular life support. Before 113 the study, the ambulance staff participating in the trial were 114 instructed how to evaluate patients with chest pain (with a 115 presumptive diagnosis of ACS) at the scene and administer 116 acetylsalicylic acid, sodium heparin, nitroglycerine and 117 narcotics if necessary. It was also routine practice for the 118 ambulance service units to record a 12-lead ECG with a 119 conventional ECG machine at the scene. The recording and 120 transmission of the TTECG to the PCI centre were not 121mandatory, but were at the discretion of the paramedics. The 122farthest point of service from the primary PCI centre (the 123Institute of Cardiology at the University of Debrecen) was 124about 110 km. 125The units were instructed how to triage patients with chest 126pain, independently if possible, and to transport all eligible 127patients with a prehospital diagnosis of STEMI directly to 128the PCI centre, bypassing the emergency departments at the 129county hospitals. Patients with an onset of typical symptoms 130b12 hours and an ST segment elevation of ≥1mmin≥2 131contiguous leads on the prehospital 12-lead ECG were 132considered eligible. The prehospital diagnosis of STEMI was 133established exclusively by the ambulance team. 134Recording and transmission of the TTECG required about 1353 minutes and, after transmission of the ECG signal (in about 13650 seconds) following digital-analogue conversion (FM 137tone), all of the important clinical data on the patient 138(including the ECG findings) and the patient’s transport were 139discussed in a brief consultation. The standard protocol of 140the consultation included registration of the patient’s 141personal data, reception of the recorded ECG and a brief 142patient referral revealing relevant clinical data. All TTECG 143data transmission was carried out via the radiotelephone 144system of the National Ambulance Service (Tetra). Upon 145arrival at the PCI centre, all patients were immediately 146interviewed and examined by a cardiologist and the 147diagnosis of STEMI was confirmed. The patients were 148then immediately transferred to the catheterization laboratory 149for primary PCI. All conventional and necessary drug 150treatment for the patients was allowed and the decisions as to 151treatment were made by the medical team at the PCI centre. 152The TTECG-assisted group referred by the ambulance 153service consisted of 397 patients with STEMI (TTECG 154group). The control group comprised a cohort of 378 patients 155with STEMI who were transported by the ambulance service 156to the PCI centre without TTECG. As concerns the controls, 157the ECGs, the clinical evaluations and the transport decision, 158together with the medical therapy provided, were carried out 159by the ambulance service staff without consultation by 160TTECG. In these cases, the PCI centre was given only a brief 161notice about the patient transfer via the regular telephone. 162All emergency patients for whom the final diagnosis was 163other than STEMI were excluded from the database of the 164present study. 165The primary efficacy outcomes were the ambulance 166service contact and transport times and the PCI-related delay 167times (door to sheath insertion and door to balloon times). 168The ambulance service contact time was defined as the time 169spent at the scene by the ambulance unit (from the first 170medical contact to the departure from the scene to the PCI 171centre). The transport time was the duration of the journey 172from the scene to the cardiac centre. The door to sheath 173insertion and door to balloon times were defined as the time 174between the arrival of the ambulance service unit at the PCI 175centre and the insertion of the sheath or balloon in the 176catheterization laboratory. The key secondary efficacy 177outcome was the in-hospital mortality rate. 178Data were collected for the study with the written 179approval of the patients. Data handling and collection were 2G. Papai et al. / Journal of Electrocardiology xx (2014) xxx–xxx UNCORRECTED PROOF 180 approved by the institutional review boards of the Institute of 181 Cardiology at the University of Debrecen and the Hungarian 182 National Ambulance Service. 183 Statistical analysis was carried out with the GB-Stat 184 v8.0 program. Depending on the type of variable 185 (qualitative or quantitative parameters), the descriptive 186 method applied involved the calculation of absolute and 187 relative frequencies, or the calculation of mean and 188 standard deviation (S.D.). Normally distributed continuous 189 variables were compared by Student’sttest at an αlevel of 190 5%. The parameters that were at least ordinal were 191 compared by means of the Wilcoxon rank-sum test at an 192 αlevel of 5%. For the cumulative survival analysis, the 193 Cox regression model (conditional logistic regression) was 194 used. The risk of death curves were plotted by the Kaplan195 Meier technique. 196 Results 197 Altogether 1564 ambulance-attended patients were 198 screened for chest pain during the study period of whom 199 800 were diagnosed as having STEMI in the prehospital 200 stage. The patient flow is depicted in Fig. 1. The final 201 diagnosis of STEMI was established in 775 patients. In the 202 remaining 25 patients, the ST segment elevation was due to 203 other reasons (vasospasm, myocarditis, etc.). All 25 patients 204 without STEMI were excluded from the study database. 205Finally, there were 397 patients in the TTECG group and 378 206patients in the control group. 207The baseline characteristics of the patients in the two 208groups are listed in Table 1. The two groups were relatively 209well matched as regards risk factors and previous medical 210history. There was a trend towards more patients with a 211history of previous congestive heart failure in the control 212group (p = 0.0885), but the difference was not significant. 213All patients in both groups underwent immediate cardiac 214catheterization, and PCI was performed in 381 patients 215(96%) in the TTECG group and in 351 patients (92.9%) in 216the control group. Among the patients in whom PCI was not 217performed, 7 patients were later referred for coronary bypass 218surgery and medical therapy was recommended for the 219remaining patients. Thrombolytic therapy was not prescribed 220to any patient. Moreover, no patient required emergency 221bypass surgery. 222Stents were deployed in 94.5% of the patients (Table 2) 223and platelet glycoprotein IIb/IIIa receptor inhibitors were 224used in 25.5% (25% in the TTECG group and 26% in the 225control group). There was no significant difference between 226the two groups in the stent procedural details (Table 2). 227Angiographic success was achieved in 94% of the patients 228(93% in the TTECG group and 95% in the control group) 229who underwent primary PCI. 230Details of the prehospital medical therapy are presented in 231Table 2. In the TTECG group significantly more sodium 232heparin (5000 U) and narcotics were administered. On the 233other hand, nitrates were used more frequently in the 234controls. In the cases of the other medications (acetylsalicylic 235acid and/or clopidogrel, atropine and beta-blockers), there 236was no significant difference between the two groups. 237Data on the distance from the PCI centre, the ambulance 238service contact and transport times and the PCI-related delay 239times (door to sheath insertion and door to balloon times) are 240to be seen in Table 3. The distance from the PCI centre was Fig. 1. CONSORT diagram showing the flow of patients at each stage of the data collection. Table 1 t1:1 Baseline characteristics of patients. t1:2 t1:3TTECG group (N = 397) Control group (N = 378) p value t1:4General t1:5Age (y) 60.18 ± 12.10 61.75 ± 11.46 0.0642 t1:6Men (%) 67.42 67.12 0.8669 t1:7Anterior myocardial infarction (%) 45.65 50.13 0.1429 t1:8Proportion of patients (%) with a previous history of t1:9Myocardial infarction 9.82 9.52 0.8878 t1:10Stroke 3.28 4.26 0.4733 t1:11Congestive heart failure 7.57 11.14 0.0885 t1:12PCI 8.61 7.18 0.4635 t1:13Coronary bypass surgery 1.51 1.06 0.5795 t1:14Proportion of patients (%) with previous cardiac risk factors t1:15Hypertension 66.16 69.14 0.4214 t1:16Diabetes mellitus 19.95 24.93 0.0967 t1:17Smoking 51.64 45.89 0.1284 t1:18Hypercholesterolemia 47.72 44.56 0.3779 Values are means ± S.D. or percentages of subjects. PCI = percutaneous coronary intervention. t1:19 3G. Papai et al. / Journal of Electrocardiology xx (2014) xxx–xxx UNCORRECTED PROOF 241 significantly longer for the TTECG group than for the 242 controls (55.2 ± 34.2 vs. 39.4 ± 32.2 km). Consequently, 243 the transport time proved to be slightly, but significantly 244 longer in the TTECG group. However, when the distance/ 245 transport time ratios were calculated, the speed of the service 246 was somewhat better in the TTECG group as compared with 247 the controls (1.03 vs. 0.96 km/min). 248 Both the door to sheath insertion and door to balloon 249 times were slightly, but significantly shorter in the TTECG 250 group relative to the controls (Table 3). 251 The mean length of the hospital stay for the patients in the 252 TTECG group was 6.99 days versus 6.94 days for those in 253 the control group (p = 0.8146). The in-hospital mortality 254 rate was 4.28% in the TTECG group, as compared with 255 8.44% in the control group. The Kaplan-Meier curves 256 indicated that there was a significant survival benefit for 257 cumulative survival at 10 days (log rank test, p = 0.0350; 258 Fig. 2) in the TTECG group in comparison with the controls. 259Discussion 260ECG changes in acute myocardial infarction are highly 261dynamic. The very early acquisition and transmission of 262ECG data in acute myocardial infarction can therefore 263provide valuable, time-sensitive data that can help increase 264the accuracy of diagnosis by showing serial ECG changes 265starting at an earlier point in time than would otherwise be 266possible. It clearly emerged from this study that an integrated 267multidisciplinary regional approach in which paramedics, 268either independently or after TTECG-based consultation 269with cardiologists, perform triage and transport patients with 270STEMI to a designated PCI centre for primary PCI, is 271feasible and fast. Interestingly, the study revealed a 272significantly lower in-hospital mortality rate for the 273TTECG group. This somewhat unexpected finding was 274probably due to improved prehospital medical therapy, and 275at least in part to the faster in-hospital reperfusion (improved 276PCI-related delay times). 277In accordance with previous observations [13], indepen278dently from a consultation with the cardiologist (TTECG 279group), the paramedics interpreted the ECG with an 280acceptable degree of accuracy and transported the patients 281immediately to the designated centre for primary PCI. 282However, significant differences between the groups were 283noted in the prehospital medical therapy initiated by the 284paramedics. Sodium heparin and narcotics were used more 285frequently after the TTECG-based consultation. It seems that 286the consultation with the specialist rather supported the 287presumptive diagnosis of STEMI, and the ambulance service 288unit accordingly initiated more aggressive medical therapy. 289In the controls (without TTECG-based consultation), there 290tended to be an underuse of sodium heparin and narcotics, 291and an overuse of nitrates, and it is hypothesised that the 292latter might have been a therapeutic excuse. 293The ASSENT-4 PCI trial [14] highlighted that the 294suboptimum antithrombotic prehospital co-therapy (under295use of sodium heparin and other antithrombotic drugs) in the 296facilitated PCI arm was responsible for the poorer clinical Table 2t2:1 Stent procedural details and prehospital medical therapy.t2:2 t2:3TTECG group (N = 397) Control group (N = 378) p value t2:4Stent procedural details t2:5Stent/patient (mean ± S.D.) 1.31 ± 0.88 1.28 ± 0.57 0.5658 t2:6Drug-eluting stent (%) 4.53 5.03 0.7423 t2:7*LAD (%) 50.87 52.56 0.7136 t2:8*CX (%) 16.76 16.31 0.8936 t2:9*RCA (%) 43.35 41.39 0.7430 t2:10 Proportion of patients (%) receiving the following prehospital medical therapy t2:11 Acetylsalicylic acid and/or clopidogrel 80.51 75.93 0.1453 t2:12 Sodium heparin 84.30 59.10 b0.0001 t2:13 Nitroglycerine 4.81 13.75 b0.0001 t2:14 Narcotics 56.99 13.76 b0.0001 t2:15 Atropine 6.84 4.23 0.1148 t2:16 Beta-blocker 4.23 3.70 0.3571 t2:17 Proportion of patients resuscitated (%) 8.56 8.27 0.8818 Values are means ± S.D. or percentages of subjects. *Patients may have had interventions on more than one vessel. LAD indicates left anterior descending; CX, left circumflex; RCA, right coronary artery. “Patients resuscitated”are the patients in whom defibrillation was needed during the first medical contact and/or transport.t2:18 Table 3t3:1 Primary efficacy outcome and mortality data for the study population.t3:2 t3:3TTECG group (N = 397) Control group (N = 378) p value t3:4Distance from PCI centre (km) 55.2 ± 34.2 39.4 ± 32.2 b0.0001 t3:5Contact time (min) 29.31 ± 10.67 24.13 ± 13.23 b0.0001 t3:6Transport time (min) 53.75 ± 32.97 40.78 ± 21.30 b0.0001 t3:7Time from symptom onset to first medical contact (min) 224.41 ± 395.59 259.95 ± 323.51 0.2581 t3:8Door to sheath insertion time (min) 43.37 ± 18.57 46.95 ± 17.75 0.0124 t3:9Door to balloon time (min) 60.31 ± 19.50 63.73 ± 21.13 0.0426 t3:10 Hospitalisation (days) 6.99 ± 3.45 6.94 ± 3.48 0.8146 t3:11 In-hospital mortality rate (%) 4.28 8.44 0.0350 Values are means ± S.D. or percentages of subjects.t3:12 Fig. 2. Kaplan-Meier curves depicting in-hospital survival at 10 days in the two groups. The number at risk indicates the number of in-hospital patients at a given time point in the TTECG and control groups, respectively. 4G. Papai et al. / Journal of Electrocardiology xx (2014) xxx–xxx UNCORRECTED PROOF 297 outcome in these patients. The ASSENT-4 PCI trial drew 298 attention to the importance of adequate antithrombotic 299 prehospital therapy. Consequently, it appears likely that the 300 suboptimum antithrombotic treatment was responsible at 301 least in part for the increased mortality rate noted in the 302 present study among the control patients. Interestingly, a 303 significantly higher proportion of the control group received 304 nitrates than that in the TTECG group (13.75% vs. 4.81%). 305 However, previous large clinical trials (GISSI-3 and ISIS-4) 306 clearly showed that nitrates did not affect the mortality 307 rate [15,16]. 308 Hypothetically, an increased number of ventricular 309 fibrillation episodes requiring cardiopulmonary resuscitation 310 (CPR) in the control group would have provided a plausible 311 explanation for the higher mortality rate among these 312 patients, and could also have been the reason for the 313 paramedic team deciding against TTECG consultation, while 314 transferring the patients immediately to the PCI centre for 315 invasive investigation. However, our evaluation of the 316 occurrence of ventricular fibrillation did not reveal a 317 significantly higher level in the control group than in the 318 TTECG group (Table 2). Another explanation for the more 319 cautious use of sodium heparin might have been the higher 320 number of unconscious patients and/or the need for assisted 321 respiration in the control group (subarachnoid haemorrhage 322 can manifest as sudden loss of consciousness, even in the 323 presence of an ST segment elevation [17]). However, the 324 database did not indicate any significant differences between 325 the two groups from these aspects. 326 Faster in-hospital reperfusion was noted in the TTECG 327 group than in the controls (Table 3). The improved PCI328 related delay times were likely to be due to faster decision329 making, transfer and preparation of the patient for primary 330 PCI in the catheterization laboratory. Interestingly, TTECG 331 was used more frequently by the paramedics if the scene of 332 the patients was more distant from the PCI centre. Upon 333 inquiry, the ambulance service personnel explained this as 334 “the longer the distance from the PCI centre, the more 335 important it is to make a proper diagnosis”. 336 In summary, our findings indicate that 1) the recording 337 and transmission of TTECG and the TTECG-based 338 consultation between the paramedics and the cardiologists 339 during the first medical contact with STEMI patients are 340 feasible and fast, 2) confirmation of the diagnosis of STEMI 341 by the specialist improved the medical therapy initiated by 342 the paramedics, and 3) TTECG significantly shortened the 343 PCI-related delay times and may improve the in-hospital 344 mortality rate. 345 Limitations of the study 346 One limitation of our study is the fact that the database 347 was not randomised and a selection bias could have 348 influenced the results. We guarded against this possibility 349 in different ways. Firstly, the decision to obtain TTECG was 350 based on the discretion of the paramedics. Some teams 351 obtained and transferred TTECG from all patients and other 352 teams made it only if they had problems with the clinical 353diagnosis and/or with the interpretation of the ECG. 354Secondly, the two groups (TTECG and control) were 355relatively well matched, including risk factors, previous 356medical history, CPR, assisted respiration and cardiogenic 357shock. Thirdly, all patients with a hospital diagnosis of 358STEMI underwent cardiac catheterization independently 359from the study arm. This measure aimed against any effect 360modifier bias of the TTECG consultation. Finally, a 361relatively long inclusion time (2 years) was involved in the 362study and all patients with a hospital diagnosis of STEMI were 363included in the database. Overall, the lack of randomisation 364and the limited number of patients render it difficult to make 365comparisons and to draw firm conclusions from this study; 366nonetheless, some benefits of the regional management of 367STEMI patients by TTECG have been demonstrated. 368Acknowledgments 369We would like to express our gratitude and appreciation 370to Klara A. Toth and Ildiko B. Laszlo for their invaluable 371help in the data collection. 372 Q2References 373[1] Steg PG, James SK, Atar D, et al. ESC Guidelines for the management 374of acute myocardial infarction in patients presenting with ST-segment 375elevation. Eur Heart J 2012;33(20):2569–619. 376[2] Canto JG, Rogers WJ, Bowlby LJ, French WJ, Pearce DJ, Weaver 377WD. The prehospital electrocardiogram in acute myocardial infarction: 378is its full potential being realized? National Registry of Myocardial 379Infarction 2 Investigators. J Am Coll Cardiol 1997;29(3):498–505. 380[3] Kekes E, Edes I. 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