EKG

My elderly patient developed a new left bundle branch block following transcatheter aortic valve replacement. Is this a frequent occurrence?

FA Manian MD, MPH, , , , , , Leave a comment

Yes, conduction abnormalities, particularly left bundle branch block (LBBB), frequently complicate transcatheter aortic valve replacement (TAVR).

A 2016 systematic review and meta-analysis reported new-onset LBBB following TAVR and persisting at hospital discharge in 13.3%-37% of patients1; the incidence may be higher or lower depending on the type of prosthesis used.2,3 In the same systematic review, new-onset LBBB was associated with a higher risk of permanent pacemaker placement (PPI) and cardiac death during 1-year followup.   In another study, persistence of LBBB post-TAVR without PPM placement was associated with an increased risk of syncope, complete AV node block, and PPI, but not overall mortality.4

The underlying anatomy of the conduction system may help explain post-TAVR conduction complications. The AV node is located adjacent to the membranous septum, closely associated with the subaortic region and LV outflow track, giving rise to the LBB.5 Protrusion of TAVR prostheses into the LV outflow tract, the mechanical injury occurring during the predilation or the positioning of the valve, and potential trauma to the conduction system by the catheters and guidewires used in TAVR may all contribute to these complications.3,5

References

  1. Regueiro A, Altisent OA, Del Trigo M, et al. Impact of new-onset left bundle branch block and periprocedural permanent pacemaker implanation on clinical outomces in patients undergoing transcatheter aortic valve replacement: A systematic review and meta-analysis. Circ Cardiovasc Interv 2016;9:e003635. http://circinterventions.ahajournals.org/content/9/5/e003635.long
  2. Nazif, T.M., Williams, M.R., Hahn, R.T., Kapadia, S., Babaliaros, V. et al. Clinical implications of new-onset left bundle branch block after transcatheter aortic valve replacement: analysis of the PARTNER experience. Eur. Heart J. 2014;21:1599-1607. https://www.ncbi.nlm.nih.gov/pubmed/24179072
  3. Bourantas CV, Serruys PW. Evolution of transcatheter aortic valve replacement. Circ Res 2014;114:1037-1051. http://circres.ahajournals.org/content/114/6/1037
  4. Urena, M., Mok, M., Serra, V., Dumont, E., Nombela-Franco, L. et al. Predictive factors and long-term clinical consequences of persistent left bundle branch block following transcatheter aortic valve implantation with a balloon-expandable valve. J Am Coll Cardiol. 2012;60:1743-1752. https://www.ncbi.nlm.nih.gov/pubmed/23040577
  5. Piazza, N., Jaegere, P., Schultz, C., Becker, A.E., Serruys, P.W., Anderson, R.H. Anatomy of the aortic valve complex and its implications for transcatheter implantation of the aortic valve. Circ Cardiovasc Interv. 2008;1:74-81. https://www.ncbi.nlm.nih.gov/pubmed/20031657

Contributed by Salvatore D’Amato MD, Mass General Hospital, Boston, MA

My elderly patient developed a new left bundle branch block following transcatheter aortic valve replacement. Is this a frequent occurrence?

How accurate is EKG when evaluating for left ventricular hypertrophy (LVH)?

FA Manian MD, MPH, , , , , , , Leave a comment

A systematic review comparing 6 EKG criteria for LVH (including commonly used Sokolow-Lyon [defined below], Cornell voltage index or product, Gubner, and Romhilt-Estes scores 4 or 5) with echocardiography reported very low median sensitivities; “highest” sensitivity was found using the Sokolow-Lyon criteria (median 21%, 4-52%). Median specificities were  89% (53-100%) and 99% (71-100%) for Sokolow-Lyon and Romhilt-Estes criteria (5 points) (1).

LVH definition of selected EKG indexes

Sokolow-Lyon index: SV1+(RV5 or V6)>35 mm 

Cornell voltage index: men, RaVL+SV3>28 mm; women, RaVL+SV3>20 mm

Modified Cornell: RaVL>11mm (>10 mm, ref. 3)

Gubner: RI+SIII>24mm

More recently, MRI has become the gold standard for in-vivo LV mass measurement. In a study involving patients with aortic stenosis undergoing MRI, EKG generally had poor negative predictive value (NPV) (<70% by most criteria), but high positive predictive value (PPV) (>90% by most criteria) for LVH; for Sokolow-Lyon criteria, the NPV and PPV were 46% and 90%, respectively (2). 

In another MRI study involving patients with various cardiovascular conditions (eg hypertension, CAD), RaVL alone (>10mm) performed better than Sokolow-Lyon (AUC 0.78, specificity 95.5%) but its sensitivity was still nothing to brag about (36.5%) (3).

So, EKGs are better at ruling in than ruling out LVH!

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References

1.Pewsner D, Juni P, Egger M, et al. Accuracy of electrocardiography in diagnosis of left ventricular hypertrophy in arterial hypertension: systematic review. BMJ 2007. doi:10.1136/bmj.39276.636354.AE  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2001078

2.Buchner S, Debl K, Haimerl J, et al.  Electrocardiographic diagnosis of left ventricular hypertrophy in aortic valve disease: evaluation of ECG criteria by cardiovascular magnetic resonance. J Cardiovasc Magn Reson  2009; 11:18. https://jcmr-online.biomedcentral.com/articles/10.1186/1532-429X-11-18

3.Courand P-Y, Grandjean A, Charles P, et al. R wave in aVL lead is a robust index of left ventricular hypertrophy: a cardiac MRI study. Am J Hypertension 2015;28:1038-48. https://www.ncbi.nlm.nih.gov/pubmed/25588700

 

Contributed in part by Khin-Kyemon Aung, medical student, Harvard Medical School, Boston.

How accurate is EKG when evaluating for left ventricular hypertrophy (LVH)?

Why should I pay attention to the augmented vector right (aVR) EKG lead in my patient with chest pain?

FA Manian MD, MPH, , , , , , , , , , Leave a comment

Lead aVR is often “neglected” because of its non-adjacent location to other EKG leads (Fig 1) and poor awareness of its potential utility in detecting myocardial ischemia.

In acute coronary syndrome (ACS), ST-elevation (STE) in aVR (≥1mm) with diffuse ST depression in other leads (Fig 2) is usually a sign of severe left main coronary artery (LMCA), proximal left anterior descending (LAD), or 3-vessel coronary disease, and is associated with poor prognosis1-3.  In some patients with LMCA thrombosis, the EKG changes may be non-specific but STE in aVR should still raise suspicion for ischemia1.  Possible mechanisms for STE in aVR include diffuse anterolateral subendocardial ischemia or transmural infarction of the basal portion of the heart. 

The possibility of an anatomical variant of the Purkinje fibers leading to the absence of STE in the anterior leads in some patients with transmural anterior infarction is another reason to pay attention to aVR.

 

Fig 1. Standard EKG limb leads. Note that aVR is “in the fringes”.

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Fig 2. 35 year old female with ACS due to LMCA spasm. Note STE in aVR with ST segment depression in leads V3-6, I, aVL, II, and aVF  (Courtesy National Library of Medicine)

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References

  1. Kossaify A. ST segment elevation in aVR: clinical syndrome in acute coronary syndrome. Clin Med Insights: Case Reports 2013:6.
  2. Kireyev D, Arkhipov MV, Zador ST. Clinical utility of aVR-the neglected electrocardiographic lead. Ann Noninvasive Electrocardiol 2010;15:175-180.
  3. Wong –CK, Gao W, Stewart RAH, et al. aVR ST elevation: an important but neglected sign in ST elevation acute myocardial infarction. Eur Heart J 2010;31:1845-1853.
  4. De Winter RJ, Verouden NJ, Wellens HJ, et al. A new ECG sign of proximal LAD occlusion. N Engl J Med 2008;359:2071-3.

 

Why should I pay attention to the augmented vector right (aVR) EKG lead in my patient with chest pain?

Is the QTc interval an accurate reflection of myocardial repolarization time in ventricular conduction defects associated with a widened QRS complex?

FA Manian MD, MPH, , Leave a comment

Ventricular conduction defects associated with a widened QRS complex—specifically, complete and incomplete bundle branch blocks—may artificially elongate the QT interval without reflecting an actual increase in myocardial repolarization time (1).

In complete bundle branch block, the widened QRS complex may elongate the QTc interval by as much as 16% while having no effect on the JT index, defined as JT interval x (heart rate+ 100)/518), where an index >112ms is considered to be prolonged (2).

Calculation of the JT index has been suggested for patients with incomplete bundle branch block, as well (2).

Put simply, in patients with ventricular conduction defects associated with a widened QRS complex, the JT index appears to be superior to the QTc interval for assessment of repolarization time.

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 References

 

1. Salik J, Muskin P. Consideration of the JT interval rather than the QT interval. Psychosomatics 2013; 54(5): 502. https://www.ncbi.nlm.nih.gov/pubmed/24034531

2. Zhou SH, Wong S, Rautaharju PM, et al. Should the JT rather than the QT be used to detect prolongation of ventricular repolarization? An assessment in normal conduction and in ventricular conduction defects. J Electrocardiology 1992; 25 (Suppl): 131-6. https://www.ncbi.nlm.nih.gov/pubmed/1297679

Contributed by Jonathan Salik, MD, Mass General Hospital, Boston, MA

 

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Massachusetts General Hospital, Harvard Catalyst, Harvard University, its affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

Is the QTc interval an accurate reflection of myocardial repolarization time in ventricular conduction defects associated with a widened QRS complex?