and Ventricular Enlargement Patterns and Clinical Associations

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© Springer Nature Singapore Pte Ltd. 2020
J. VarshneyElectrocardiography in Veterinary Medicinehttps://doi.org/10.1007/978-981-15-3699-1_7


7. Atrial and Ventricular Enlargement Patterns and Clinical Associations



J. P. Varshney1 


(1)
Veterinary Medicine, Shri Surat Panjarapole Prerit Nandini Veterinary Hospital, Surat, Gujarat, India

 



Cardiac enlargement is seen in many cardiac diseases. It can either be due to enlargement of atrium or ventricle or both. Electrocardiogram can provide confirmatory evidence of the side or chamber of the heart that is affected. Electrocardiographic features of the enlargement of different heart chambers are given below:


7.1 Normal Atrial Pattern






  • “P” wave amplitude <0.4 mV



  • “P” wave duration <0.04 s


7.1.1 Right Atrial Enlargement Pattern


“P” wave indicates atrium depolarization and its initial half stroke signifies right atrium. Hence increase in amplitude of “P” wave is suggestive of right atrium enlargement.



  • “P” wave amplitude >0.4 mV (Fig. 7.1).



  • “P” wave duration 0.04 s or less.



  • “Ta” wave (Fig. 7.2) slight depression of base line following “P” may sometimes indicate right atrial enlargement.


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Fig. 7.1

Electrocardiogram of a dog (lead II, sensitivity 1, speed 25 mm/s) showing increased amplitude of “P” wave (0.5 mV) suggesting right atrial enlargement


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Fig. 7.2

Electrocardiogram of a Pomeranian dog (lead II, sensitivity 1, speed 25 mm/s) showing depression of baseline following P, i.e., descending arm of “P” longer than ascending arm of P wave. It is called Ta wave. Sometimes it indicates right atrium enlargement


7.1.2 Left Atrial Enlargement Pattern


Later half of the “P” wave is produced by depolarization of left atrium. Hence prolonged duration of “P” wave is suggestive of left atrium enlargement.



  • “P” wave duration >0.04 s (Fig. 7.3)



  • Notched and wide “P” wave


../images/489736_1_En_7_Chapter/489736_1_En_7_Fig3_HTML.jpg

Fig. 7.3

Electrocardiogram of a dog (lead II, sensitivity 1, speed 25 mm/s) showing broad “P” (0.08 s) suggesting left atrium enlargement


7.1.3 Biatrial Enlargement Pattern


Total “P” wave is the contribution of depolarization of both right and left atrium, therefore an increase in “P” wave’s height and duration is suggestive of biatrial enlargement.



  • “P” wave amplitude >0.4 mV and duration >0.04 s (Fig. 7.4)



  • Notching or slurring of “P” may be present


../images/489736_1_En_7_Chapter/489736_1_En_7_Fig4_HTML.jpg

Fig. 7.4

Electrocardiogram of a dog (lead II, sensitivity 1, speed 25 mm/s) showing increased amplitude (>0.4 mV) and prolonged duration of “P” (0.08 s) suggesting biatrial enlargement


7.2 Normal Ventricular Pattern (Fig. 7.5)






  • Mean electrical axis within +40° to +100°



  • No “S” wave in lead I



  • “R” wave in lead II is taller than that of lead I



  • “R” wave in lead CV6LL is larger than “S”


../images/489736_1_En_7_Chapter/489736_1_En_7_Fig5_HTML.jpg

Fig. 7.5

Electrocardiogram of a dog (lead, I, II, III, aVR, aVL, aVF, sensitivity 1, speed 25 mm/s) showing no “S” wave in lead I and “R” wave taller in lead II and III than lead I suggesting normal ventricular pattern


7.2.1 Right Ventricular Enlargement Pattern


“Q” and “S” waves represent right ventricular depolarization. Hence changes related to these waves are suggestive of right ventricle enlargement. Only one criterion is not sufficient to say right ventricle enlargement. For confirming right ventricular enlargement, at least three criteria should be present in the ECG. The following are the accepted criterion that indicates change in the size of right ventricle:



  • Deviation of mean electrical axis (>+100°) on frontal plane



  • Presence of “S” wave in lead I (more than 0.05 mV) (Fig. 7.6)



  • Presence of “S” wave in lead II (more than 0.35 mV) (Figs. 7.7 and 7.8)



  • Presence of “S” wave in lead III (Fig. 7.6)



  • Presence of “S” wave in lead aVF (Fig. 7.6)



  • Presence of “S” wave in lead CV6LL (more than 0.8 mV) (Fig. 7.6)



  • Presence of “S” wave in lead CV6LU (more than 0.7 mV)



  • Large “S” wave with normal “R” in lead CV6LU alters the R:S ratio. Ratio of <0.8 is suggestive of right ventricular enlargement



  • W-shaped “Q-S” in lead V10



  • Positive “T” wave in lead V10 in dogs (Fig. 7.9) other than Chihuahua breed is also suggestive of right ventricular enlargement



  • Large “Q” wave (amplitude more than 0.5 mV) in lead II, III, and aVF (Fig. 7.10)

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Jul 17, 2021 | Posted by in INTERNAL MEDICINE | Comments Off on and Ventricular Enlargement Patterns and Clinical Associations

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