JUGULAR VENOUS WAVEFORMS AND CAROTID PULSATIONS IN TACHYARRHYTHMIA DIAGNOSIS: A READILY AVAILABLE BUT OFTEN FORGOTTEN TOOL
Background
The content of this post was written by me few years ago. It builds conceptual framework on JVP and carotid wave analysis for tachyarrhythmia diagnosis. Many concepts written in this post are practical with a bit of practice and spending time with patients. The techniques written here can be used as important adjunct to 12 lead surface ECG tracing in diagnosing tachyarrythmia.
You are requested to read and understand the content and give your frank comments.
Introduction
Tachyarrhythmia diagnosis is a challenge that all of us face as daily routine. Usually it requires a good and fast analysis of surface ECG. This article discusses different aspects of using clinical examination especially jugular venous waveforms (JVW) and carotid pulsations (CP) in diagnosis of arrhythmias. Many of the techniques seem to be impractical and be of academic interest only but a lot of them fare better chances in accurate and rapid diagnoses of arrhythmias than using a 12 lead surface ECG.
JVWs and ECG correlation in sinus rhythm
ECG gives us the electrical activity of whole heart during cardiac cycle and JVWs and CPs give us mechanical activity during cardiac cycle.
Usually the mechanical activity follows the electrical activity (depolarization) by a few milliseconds. The following are the correlation of phase of cardiac cycle and the ECG waveforms:
| Cardiac cycle | ECG waveforms | Electrical cycle |
|---|---|---|
| Ventricular systole (0.3 secs) | Q – T interval (start of QRS to end of T), only approximately | Vent depolarization + vent repolarization (Stage 1, 2, 3) |
| Ventricular diastole (0.5 secs) | T – Q interval | Stage of resting membrane potential (Stage 4) |
| Atrial systole | P wave or PR interval (approximately) | Atrial depolarization |
JVWs are formed due to mechanical activities inside the atria and they may or may not be dependent on mechanical activities of ventricles. CPs are solely due to ventricular systole.
'a' wave
It is solely due to atrial contraction, irrespective the mechanical state of the ventricle. It corresponds to atrial depolarization and P wave in ECG. If atrial contraction takes place against closed AV valves, usually when the ventricle is also in systole, ‘a’ wave’s amplitude increases and is known as cannon wave. In sinus rhythm, it is recognized as positive wave appearing just before carotid pulse. In tachyarrhythmias, it is usually the only positive wave seen in the jugular veins, as v wave is submerged being the smaller wave and due to shortened ventricular systole.
'x' descent
It corresponds to the start of ventricular systole and corresponds to ventricular depolarization and QRS complex in ECG. It is not a good indicator of ventricular systole as it may get modified depending on the mechanical state of atrium, e.g. in very early atrial premature beat, when ventricle is still in systole, it may be superimposed with a very premature a wave (cannon wave).
'v' wave
It occurs in late ventricular systole and is a slow rising positive wave. It is the only positive wave seen in atrial fibrillation. In tachyarrhythmias, it is usually not appreciated because of reasons cited above.
Carotid pulsation
CP is caused solely due to ventricular contraction and therefore represents ventricular systole and QRS complex in ECG.
To summarize, ‘a’ wave can be considered to be representative of P wave and carotid pulsation of QRS complex. Other waveforms do not serve much purpose in tachyarrhythmia diagnosis as they depend on combined synchronized activity of atrium and ventricle, which usually do not take place in cases of arrhythmias.
Recognition of ‘a’ wave during tachyarrhythmia
JVWs are always appreciated in supine position with patient’s neck in neutral position. In thick, short necked individuals it becomes prominent after extending the neck. Sometimes, it is better appreciated during inspiration. It is usually differentiated from CP by the fact that JVWs are better seen then felt, unlike CPs. Other characters do not hold good (like two positive waves in a cardiac cycle) or are difficult to appreciate (like changes with respiration and posture) in cases of arrhythmias.
Presence of two positive waves in jugular vein per cardiac cycle with regular CPs suggests sinus rhythm and recognition of the waveforms are as already described. In tachyarrhythmias (fast CPs), the only positive waves seen are a waves, v waves being submerged.
Clinical classification of arrhythmias
The following are the common clinical types of tachyarrhythmias:
Premature beats in midst of regular CPs (Aim: to differentiate between atrial, nodal and ventricular premature beats)
Irregularly irregular CPs of varying volumes (Aim: to differentiate between atrial fibrillation, multiple premature beats, atrial flutter with variable conduction and multifocal tachycardia)
Regular fast CPs [Aim: to differentiate between supranodal, nodal and infranodal (AV dissociation present) tachycardia]
Clinical recognition of AV dissociation (AVD)
AVD signifies regular and independent electrical, so mechanical, activity of atrium and ventricle. It usually occurs due to physiological or pathological blockage of conduction through AV node. Atrial systole can occur during any of the phases of ventricular cycle. Each ventricular systole is preceded by ventricular diastole with variable filling due to variable state of atrium resulting in a beat to beat variability of carotid volume and systolic blood pressure. Although ‘a’ waves are regularly placed, their volume also vary and when atrial and ventricular systole occur simultaneously, cannon waves are produced which occur irregularly by chance.
Clinical recognition of retrograde conduction (RC)
Retrograde conduction denotes electrical activation of atrium retrogradely following activation of AV node (nodal rhythm) or ventricle (infranodal rhythm). It usually occur in conditions where (infra) nodal rate is faster than the sinus rate, due to which the retrograde impulse has got a receptive AV node more often. Once the distal impulse gets conducted retrogradely through AV node discharging sinus node, sinus node does not get chances to take over resulting in regular occurrence of retrograde conduction. If the (infra) nodal rate is slower than the sinus rate, chances that the distal impulse will get receptive AV node is much less and even if it finds one, it is not sustained as sinus impulse takes over eventually. In conditions involving the first mechanism, atrial systole occurs during ventricular systole (after a few milliseconds) regularly, generating regular cannon waves, whose rate is same as that of CPs. In conditions involving second mechanism, ‘a’ waves are irregular (due to occasional premature discharge of sinus node) with irregular cannon waves (c.f. AVD where irregular cannon waves are associated with regular ‘a’ waves).
Approach to diagnosis of tachyarrhythmias
The first step is to analyze CPs for regularity and amplitude. Next step is to sub-classify rhythm as under mentioned and proceed:
Premature beats in midst of regular CPs
Conditions to be differentiated are atrial, nodal or ventricular premature beats. Usually differentiating between all these conditions are difficult as premature beats are occasional (resulting in failure to anticipate it and the findings) and in between we have got both ‘a’ and ‘v’ waves. Atrial premature beat (APB) is characterized by premature ‘a’ wave, which if very premature can occur while ventricle is still in systole (P’ occurring on preceding T wave) resulting in premature cannon wave. The corresponding CP is low in volume or absent (if APB finds AVN in state of refractoriness). The same findings will also be there in nodal or ventricular premature beats if there is retrograde conduction to atrium (except that in these cases the premature ‘a’ wave will always be a cannon wave). But in classic nodal and ventricular premature beats, the premature impulse finds a refractory AVN. This results in regularly placed ‘a’ wave, which usually is a cannon wave as atrial systole occurs at the time when ventricle is in systole.
Irregularly irregular CPs
The diseases can be further subdivided into two categories depending on the CP rate:
CP rate < 100/min: Main differentials are atrial fibrillation, atrial flutter with variable conduction and multiple premature beats. Since the CP rate is less than 100/min, we can distinguish the JVWs with relative ease. If there is only one positive wave per cardiac cycle (between two CPs), the diagnosis is atrial fibrillation. If we appreciate two positive waves in a cardiac cycle, the diagnosis is premature beats. If there is occasional cannon wave, the diagnosis is nodal/ventricular premature beat. In atrial flutter, we can appreciate multiple regular, positive waves (multiple ‘a’ waves rate of which will be same as atrial rate in ECG), some of which will be cannon waves. 2:1 conduction, where there will be only two positive waves per cardiac cycle, will not be considered in this subgroup as CP rate is more than 100/min.
CP rate >= 100/min: Main differentials are atrial fibrillation, multifocal atrial tachycardia and atrial flutter with fast conduction. Differentiating conditions in this group is difficult because of fast ventricular as well as atrial rate, which results in difficulty in appreciating number of positive waves per CP cycle. Otherwise, the logic behind differentiating the abovementioned conditions are same as for conditions where CP rate is less than 100/min.
Regular fast CPs
This group consists of diseases that are life threatening, and for those proper diagnosis is required before initiating treatment. Proper clinical examination, in this sub group, can sometimes yield more information than ECG analysis.
Main differentials in this subgroup are:
Without AVD (supraventricular tachycardia)
a. Sinus/atrial tachycardia, atrial flutter with regular fast conduction
b. AVNRT/AVRT
c. Ventricular tachycardia with RC
With AVD (ventricular tachycardia)
a. Typical ventricular tachycardia
The main differentiating feature between ventricular versus supraventricular tachycardia is the presence of AVD in former and absence in later conditions. When wide QRS complex tachycardia is analyzed to differentiate between two sub groups using ECG, AVD is not usually appreciated as P waves get merged within rapidly occurring widened QRS complexes or T waves. So, we concentrate on the morphological characteristics of QRS complex, which are less accurate. In clinical method, AVD can easily be appreciated and so emphasis is placed on detection of the same.
As was earlier noted, AVD is characterized by regular ‘a’ waves, rate of which is different from rate of CP, whose amplitude keeps on varying depending on the state in which the ventricle is in and sometimes (irregularly) as cannon waves when ventricle is in systole. In ventricular tachycardia, for one atrial cycle (time period between two consequent atrial systoles or ‘a’ waves) ventricle undergoes more than one cycles (usually 2 – 3). Each ventricular cycle will produce separate ‘x’, ‘v’ and ‘y’ descent whose amplitude will differ depending on the atrial state. The JVP is characterized by multiple positive waves of variable amplitudes per atrial cycle (ventricular cycle is too fast to be appreciated). Only waves that can be easily appreciated are the cannon waves, which are irregular. CP amplitudes are appreciated as equal as their rate is fast and atrial state is more or less same for each ventricular filling phase. So, in the presence of rapid CPs, the only easily discernable clinical evidence of AVD and thus, ventricular tachycardia is presence of irregular cannon waves.
Second subgroup of tachycardia, which include AVNRT/AVRT and ventricular tachycardia with retrograde conduction is characterized by almost simultaneous, rapid atrial and ventricular systole. This is appreciated in jugular veins as regular, rapid cannon waves (frog sign). All other waveforms are not appreciated.
Third subgroup, which include atrial and sinus tachycardia, do not produce any cannon waves. These conditions are difficult to differentiate from atrial flutter with fast conduction (2:1), which will also have two positive waves per cardiac cycle. In atrial flutter, however, few of ‘a’ waves will be cannon waves (regularly occurring).
The clinical methods described above are quite effective in differentiating different tachycardias, especially between supraventricular and ventricular tachycardia. It however cannot differentiate between ventricular tachycardia with retrograde conduction and AV (N) RT which obviously have different treatment strategies.
Conclusion
This article describe in brief the approach to differentiate different tachyarrhythmias by observing patient’s JVWs and CPs without aid of surface 12 lead ECG. The methods described above can lead to pretty accurate and rapid diagnoses and can sometimes supplement ECG tracing in reaching accurate diagnosis. The advantage with clinical method is that we observe JVWs (atrial activity) and CPs (ventricular activity) as two separate tracings (more like tracings during electrophysiological study) unlike in surface ECG, where both atrial and ventricular activity is merged in a single tracing leading to some important information getting missed.
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