EMS World

DEC 2014

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CE ARTICLE DIFFERENTIATING BETWEEN LVH AND STEMI Differentiating bet ween LVH and STEMI can be difficult. A true STEMI will have reciprocal ECG changes, while ST-segment elevation secondary to LVH will not. As detailed in the ECG criteria ab ove, LV H usually present s with ST-segment elevation in the anterior leads. Therefore, ST-segment eleva- tion in the inferior, lateral, right-sided or posterior leads should be considered a STEMI. The true difficulty lies in differen- tiating an anterior MI from LVH. A group out of University of California-Davis has put together an algorithm to better predict which ST-segment elevation in LVH is a true STEMI. 16 This algorithm has not yet been validated, and the authors acknowledge it "may augment interpre- tation" but is by no means definitive. The authors found that measuring the relative amount of ST-segment eleva- tion was more sensitive and specific for STEMI than measuring the absolute ST-segment elevation. To determine the relative ST-segment elevation, it is normalized against the difference of the preceding R- and S-waves to give a percentage (%STE). In this calcula- tion, %STE = (height of T-P segment to J-point)/(height of R-wave minus depth of S-wave). The authors found that legitimate STEMIs had a greater percent STE versus false STEMIs in LVH. If the percent STE was less than 25%, a STEMI could be ruled out. If the percent STE was greater than 25%, the sensitivity and specificity for legitimate STEMI were 77% and 91%, respectively. The steps involved in using the algo - rithm are as follows: 1. Are the ST elevations in leads V1–V3? If yes, go to step 2. If they're in other leads, it's a STEMI. 2. Is the %STE greater than 25%? If no, it's not a STEMI. If yes, go to step 3. 3. Are there more than three leads with ST elevation? If yes, it's a STEMI. If no, go to step 4. 4. Are the T-wave inversions present in V1–V3? If yes, it's a STEMI. If no, it's not a STEMI. Using these criteria, the patient in our case does not meet the criteria for STEMI. Her ST-segment elevation can be considered normal with her LVH. In addition, while she has weakness and dizziness, and as an elderly diabetic female we would expect her to present with atypical chest pain with AMI, her histor y and clinical exam strongly suggest that she may be dehydrated from long hours working in a warm environment. TREATMENT In the absence of true STEMI, there is no treatment for the ECG manifesta- tions of LVH. Treatment of the patient in this case should focus on her weakness and dizziness, and these complaints warrant ALS -level care. Administer ox ygen if necessar y via the appro - priate device and flow rate to maintain an oxygen saturation of at least 94%, obtain intravenous access, and a fluid challenge could be administered in an attempt to increase her blood pressure. Place the patient on a cardiac monitor and obtain serial 12-lead ECGs en route to the emergency department, just to be certain the ST-segment elevation is not evolving or that reciprocal changes don't emerge, both of which would indi- cate an evolving STEMI. Conclusion Hopefully, this month's CE article reinforc ed the message from last month: STEMI imitators can be readily identified with a good understanding of the HPI, a thorough clinical exam and an understanding of the ECG patterns typical for the imitators. If a patient presents with a suspected STEMI imitator, if there is any change in their symptoms or there are persistent clin- ical symptoms suggestive of AMI in the presence of a suspected STEMI imitator, perform serial ECGs. If you find your- self wanting to identify a 12-lead ECG pattern as a STEMI imitator, continue to reevaluate and perform serial ECGs! When in doubt, always err on the side of caution: Call it a STEMI and treat it as such. REFERENCES 1. Birnie D, Williams K, et al. Reasons for escalating pacemaker implants. Am J Cardiol, 2006; 98(1): 93. 2. Hayes DL. Indications for permanent cardiac pacing. UpToDate.com, www.uptodate.com/contents/indications- for-permanent-cardiac-pacing. 3. Brubaker PH, Kitzman DW. Chronotropic incompetence: causes, consequences, and management. Circulation, 2011; 123: 1,010–20. 4. Prutkin JM. ECG tutorial: Pacemakers. UpToDate.com, www.uptodate.com/contents/ecg-tutorial-pacemakers. 5. Sgarbossa EB, Pinski SL, et al. Early electrocardiographic diagnosis of acute myocardial infarction in the presence of ventricular paced rhythm. GUSTO-I investigators. Am J Cardiol, 1996; 77(5): 423. 6. Goldberger AL. Electrocardiographic diagnosis of myocardial infarction in the presence of bundle branch block or a paced rhythm. UpToDate.com, www.uptodate. com/contents/electrocardiographic-diagnosis-of- myocardial-infarction-in-the-presence-of-bundle-branch- block-or-a-paced-rhythm. 7. Kudenchuk PJ, Maynard C, et al. Utility of the prehospital electrocardiogram in diagnosing acute coronary syndromes: the Myocardial Infarction Triage and Intervention (MITI) Project. J Am Coll Cardiol, 1998; 32(1): 17. 8. Chalela JA, Jacobs TL. Cardiac complications of stroke. UpToDate.com, www.uptodate.com/contents/cardiac- complications-of-stroke. 9. Burns E. Raised intracranial pressure. Life in the Fast Lane, http://lifeinthefastlane.com/ecg-library/raised- intracranial-pressure/. 10. Singer RJ, Ogilvy CS, Rordorf G. Clinical manifestations and diagnosis of aneurysmal subarachnoid hemorrhage. UpToDate.com, www.uptodate.com/contents/ clinical-manifestations-and-diagnosis-of-aneurysmal- subarachnoid-hemorrhage. 11. Goldberger AL. Electrocardiographic diagnosis of left ventricular hypertrophy. UpToDate.com, www.uptodate. com/contents/electrocardiographic-diagnosis-of-left- ventricular-hypertrophy. 12. Podrid PJ. Left ventricular hypertrophy and arrhythmia. UpToDate.com, www.uptodate.com/contents/left- ventricular-hypertrophy-and-arrhythmia. 13. Burns E. Left ventricular hypertrophy. Life in the Fast Lane, http://lifeinthefastlane.com/ecg-library/basics/left- ventricular-hypertrophy/. 14. Brady WJ, Perron AD, et al. Cause of ST segment abnormality in ED chest pain patients. Am J Emerg Med, 2001 Jan; 19(1): 25–8. 15. Prutkin JM. ECG tutorial: Chamber enlargement and hypertrophy. UpToDate.com, www.uptodate.com/contents/ ecg-tutorial-chamber-enlargement-and-hypertrophy. 16. Armstrong EJ, Kulkami AR, et al. Electrocardiographic criteria for ST-elevation myocardial infarction in patients with left ventricular hypertrophy. Am J Cardiol, 2012 Oct 1; 110(7): 977–83. Scott R. Snyder, BS, NREMT-P, is full-time faculty at the Public Safety Training Center in the Emergency Care Program at Santa Rosa Junior College, CA. He is also a paramedic with AMR: Sonoma Life Support in Santa Rosa, CA. E-mail scottrsnyder@ me.com. Sean M. Kivlehan, MD, MPH, NREMT-P, is an emergency medicine resident at the University of California, San Francisco. E-mail sean.kivlehan@ gmail.com. Kevin T. Collopy, BA, FP-C, CCEMT-P, NREMT-P, WEMT, is performance improvement coordinator for VitaLink/AirLink in Wilmington, NC, and a lead instructor for Wilderness Medical Associates. E-mail kcollopy@colgatealumni.org. EMSWORLD.com | DECEMBER 2014 95

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