ECG Exercise 9 - ECG Pearls

This is an example of Bidirectional VT, which is a type of Polymorphic VT with beat to beat alteration of 2 QRS morphologies

• Seen with: digoxin overdose, myocarditis, cardiac sarcoid, catecholaminergic PVT, Andersen-Tawil syndrome, acute ischemia, chronic infarcted MI, familial hypokalemic periodic paralysis, herbal aconite and caffeine poisoning, LQTS7, cardiac tumors
• For more info: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9188370/

• Answer: Pulmonary Embolism
• Look for:
• New TW inversion (V1-V4, inferior leads especially III)
• Sinus tachycardia
• Right axis deviation
• New RBBB or Incomplete RBBB
• ST elevations in right sided leads (V1, V2, aVR, III)
• Unfortunately there no specific findings diagnostic for PE. Retrospective data shows that ~45% of patients with confirmed PE have no sinus tachycardia, and even signs of RV strain on ECG only showed RV dysfunction on echo in 50% of patients
• Sources: 
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10724117/
• https://pubmed.ncbi.nlm.nih.gov/27742402/

• Answer: Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC, formerly ARVD)
• Inherited cardiomyopathy caused by fibrofatty myocardial replacement.
• This puts the patient at risk for ventricular arrhythmias dysfunction.
• No gold standard diagnostic test, diagnosed with complex criteria (imaging, tissue, ECG, fam hx, arrhythmia).
• ECG findings
• Epsilon wave has high specificity, but poor sensitivity (a late finding without prognostic value)
• Other findings: TW inversion V1-V3, Terminal Activation Duration (the interval between the nadir (lowest point) of the S-wave and the end of the depolarization) > 55 ms and the presence of VT
• Sources: 
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7203633/
• https://www.sciencedirect.com/science/article/pii/S2405500X21010811?via%3Dihub

• Answer: Takotsubo (Stress Cardiomyopathy)
• Basic Pathophysiology: Stress --> increased epi, norepi (preferentially to base of LV) --> myocardial toxicity --> apical ballooning (but there are different distributions, and potentially reversible)
• ECG findings
• STE (usually in anterior leads, mimics AMI)
• TW Inversions
• Prolonged QTc interval
• Les likely to have Q waves or inferior ST depressions
• However, no ECG findings can truly differentiate Takotsubo from AMI. This is a diagnosis of exclusion meaning ACS should be ruled out first.
• Sources: 
• https://pubmed.ncbi.nlm.nih.gov/33482618/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3956807/

• Answer: Sodium Channel Toxicity
• Mechanism: medication blocks Na channels in cardiac tissue --> remain open --> delays phase 0 depolarization/prolongs QRS
• ECG Findings
• Terminal R in aVR (> 3mm or R/S > 0.7)
• Terminal S wave in lateral leads
• Right axis deviation
• Prolonged QRS, prolonged QTc
• Tachycardia
• ECG findings predicting seizure / arrhythmia
• Tall R wave is somewhat reliable predictor of seizure/arrhythmia (sen: 81%; spec: 73%)
• QRS > 100 elevated risk of seizures (sen: 82%; spec: 58%) - caveat that this data is from TCA overdoses
• Remember to call your local Poison Control center
• Sources:
• https://pubmed.ncbi.nlm.nih.gov/4022081/
• https://pubmed.ncbi.nlm.nih.gov/7618783/
• https://pubmed.ncbi.nlm.nih.gov/17606094/

• Answer: Dextrocardia
• ECG Findings: 
• Right Axis Deviation of P waves and QRS complex (particularly lead I). Upright aVR. 
• Reversed R wave progression (differentiates from lead reversal, as this should have preserved R wave progression)
• Doesn't necessarily change management, but when screening ECGs, P wave in I should always be upright, and aVR should generally have a negative P wave and QRS. If not --> search for reason
• Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6730946/

• Answer: Right atrial enlargement (RAE) from Ebstein's Anomaly
• The pediatric ECG is rarely specific for one diagnosis, but it can tip you off towards an underlying cardiac pathology
• Here the P waves are very tall typical of RAE. Normal, P waves should be small and one wave.
• This abnormality should prompt you to search for a reason (echo, cards consult, etc). In Ebstein’s anomaly, there is inferior displacement of tricuspid valve into the RV with right to left shunt through atrial septal defect. This can cause enlargement of right atrium.

• Answer: Normal
• Pediatric ECGs have two major themes: R wave and T wave progression. We'll discuss R wave progression here
• During neonatal period (0-1 month), RV is dominant force --> V1 R wave dominant, V6 S wave dominant
• The RV begins to shrink and LV enlarges during infant stage (0-3 years) --> V1 R wave dominant, V6 now R wave dominant
• By age 2-3, LV now most dominant force, now adult pattern --> V1 S wave dominant, V6 R wave dominant

• Answer: Hyperkalemia
• Any time you have a bizarre wide complex QRS, consider hyperK
• Serum K levels don't always correlate with "expected" ECG findings, and a normal ECG does not r/o hyperK (especially in patients with ESRD)
• Though we often reflexively treat ECGs with isolated peaked T waves with Calcium, it is really features such as wide QRS, severe bradycardia, PR prolongation, and 2nd/3rd degree heart blocks that are truly at higher risk.
• Severe hyperK can cause both ACS (ST elevations as above) and Brugada mimics
• Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9301030/#b17

• Answer: Hypokalemia
• Common ECG findings:  U waves, prolonged QTc, T-wave flattening/inversions, ST depressions, PAC/PVCs
• Expect to see in 40% of patients with K < 3.5, up to 75% when K <2.5
• Be concerned for VT, TdP, and VF, butwe may be overestimating this risk
• Source: https://pubmed.ncbi.nlm.nih.gov/38098171/

• Answer: RBBB+LAFB from an anterior OMI
• The Right Bundle Branch and Left Anterior Fascicle are both perfused by septal branches of the LAD. Proximal occlusion of LAD sometimes may manifest as a new RBBB + LAFB
• No Sgarbossa's criteria for RBBB and ischemia, but there should be proportionate ST depressions in V1-V3. Keep an eye out for abnormal Q wave, subtle ST elevations, and have a high clinical suspicion for Cardiogenic Shock
• In this ECG, there are STE in avL and V1-V2 in addition to RBBB+LAFB
• Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8142368/

• Answer
• Interpretation: Sinus rhythm w/ bifascicular block (RBBB+LAFB) & 1st degree AVB
• Dispo: admission for EP study
• Explanation
• With right bundle branch and left anterior fascicle blocked, only the left posterior fascicle is available to transmit conduction from atria to ventricle
• Left posterior fascicular gets transiently knocked out --> complete AVB --> syncope
• Patients with bifascicular blocks +/- 1st degree AVB WITH SYNCOPE need EP Study and likely pacemaker (decreases future rate of syncope, but not mortality). If no symptoms, have patient f/up outpatient
• 1st degree + RBBB+LAFB is often misidentified aas a trifasicular block. This is a misnomer. The AV node is not a fascicle.
• Source: https://blog.clinicalmonster.com/2023/09/29/couldnt-find-a-catchy-title-but-we-trifasciculared/

Answer: Sinus tachycardia, peaked T waves, K of 6.3

• This patient was suffering from heat stroke with associated rhabdomyolysis and hyperkalemia
• Heat stroke commonly causes sinus tachycardia, but may cause arrhythmias such as atrial fibrillation and SVT. In severe cases, may even cause VT and cardiac arrest
• Treat as you normally would, knowing that a case report demonstrated effective cardioversion of a patient with VT while still submerged in ice water
• Source: https://pubmed.ncbi.nlm.nih.gov/36334955/