A basic query in LV function measurement

Which point in ECG is taken as reference for End systolic dimension for LV function assessment?

Marking the end diastolic point in ECG is quiet straight forward. Peak of R wave.(or Q)*

But, what about the reference point for end systole.

1. Descending slope of T wave
2. Peak of T wave
3. End of T wave
4. If T is absent or not clear , I will be confused
5. To be realistic, ECG has no reliable reference point for end systole.

Answer: If I say the answer is 5, no one is going to agree. Please note, the relationship between the T wave and the peak systolic phase in echocardiography is weak. Is there any relation at all ? Then, how to measure LV function in echocardiography? There is a electro-mechanical delay in every segment and sequence of cardiac contraction and relaxation, with former piping the later (electricity beats).

Surprisingly (illogically as well), we take the point of maximum thickness in M-mode as end-systolic, which, in fact, corresponds to peak mechanical systole. This point has no consistent relationship with any part of the T wave. We must realize, the clinical cardiac cycle is defined based on sounds, i.e. S1 and S2, while the biomechanical cardiac cycle is different. Similarly, echocardiographic systole is not the same as clinical systole. 2D echo eliminates this uncertainty to a large extent. This is one of the reasons , we are advised and encouraged, not to measure LV dimensions in M mode.(A very tough advice to follow though)

Final message

We are not completely clear yet, in the “ECG vs Echo” time correlation of hemodynamic events. The errors may be in only milli-seconds, still, when planning for Interventions like re-synchronisations, and in the follow up of DCM patients this could matter much.

Reference

1.Mada RO, Lysyansky P, Daraban AM, Duchenne J, Voigt JU. How to define end-diastole and end-systole?: Impact of timing on strain measurements. JACC Cardiovasc Imaging. 2015 Feb;8(2):148-57. doi: 10.1016/j.jcmg.2014.10.010. Epub 2015 Jan 7. PMID: 25577447.

2.Gill H, Hoffmann A. The timing of onset of mechanical systole and diastole in reference to the QRS-T complex: a study to determine performance criteria for a non-invasive diastolic timed vibration massage system in treatment of potentially unstable cardiac disorders. Cardiovasc Eng. 2010 Dec;10(4):235-45. doi: 10.1007/s10558-010-9108-x. PMID: 21113800.