Oct 02 2026 This Week in Cardiology

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John Mandrola (0:41)

Hi, everyone. This is John Mandrola from the heart.org Medscape Cardiology. And this is This Week in Cardiology for October 2nd, 2026 This week, an incredibly important listener feedback on the Danish-Crt trial and device therapy of heart failure. The POET-2 trial, one of the most erroneous trial interpretations I have seen. A mechanistic study in obesity and atrial fib, the DanCode trial of slowing corner artery calcium progression, and more on GLP-1 agonist drugs. So first, I've received excellent feedback on my coverage of the data CRT study, which found that during CRT device implantation by V pacing, targeting the latest QLV made no difference compared to simply placing the lead, the CS lead, in the easiest, most available posterior lateral non-apical branch. The trial found no difference in the primary outcome of death or heart failure admission, and I commented that the study showed that simple was better than complex.

Now, to briefly review, QLV is an important general cardiology concept in that it measures the delay in left ventricular activation. This delay is A, the reason that left bundle branch block or anything that causes delay of the left ventricular contraction causes mechanical dyssynchrony, and B, it's the actual target of bi-V pacing. Recall that bi-V pacing is simply electrical heart fire therapy. It is, in my belief, the number one interventional heart failure technique. It's far better and more evidence-based than say, transcatheter edge-to-edge repair or cardiac contractility modulation, for instance. So this week, doctors Jacqueline Joseph from McGill and Kevin Vernewey from Maastricht, wrote me a superb comment, and here's what they wrote about Danish-Crt.

They wrote, Investigator-initialated randomized trials like this are incredibly important, and Professor Nielsen and colleagues should be congratulated for conducting such a rigorous study, including detailed electrical mapping during CRT implantation. But we wanted to re-emphasize one point that could perhaps be lost in the discussion, the absence of a difference between an anatomically guided posterior lateral lead and strategy targeting the latest measured activation should not be interpreted as meaning that the QLV is no longer important. Danish CRT showed that specifically targeting the latest measured site did not improve outcomes over a simple stable posterior lateral position, but 22 percent, one in five patients could not ultimately be implanted at the targeted latest site because of the usual anatomic constraints, namely that a vein didn't go there. It is also unclear how often the final lead position selected by electrical mapping differed meaningfully from the position that would have been chosen anatomically. And I just want to interject that I would emphasize this point because the mean difference in QLV was only nine milliseconds longer in the intervention group. So pragmatic placement in the easiest vein is not that much worse than targeting the latest QLV.

Now, back to the writers, most of the outcome difference in CRT are from patient selection. Indeed, that's correct as well. They continue that we worry that this part of CRT implantation may gradually be lost. And we were recently disappointed to find that several EP fellows could not explain what the QLV represents. The QLV is one of the few measurements available during implantation that tells us whether the LV lead is reaching electrically delayed myocardium. Now even if we no longer need to map every coronary sinus branch searching for the latest site, we should still continue to understand and measure the electrical delay at the site where we ultimately pace. Perhaps the more relevant target is identifying the longest posterior lateral electrical delay available in an individual patient. The challenge is knowing what that delay actually is. And now here they cite that they recently described a simple non-invasive method to estimate it. And I'll cite the study. It's Joseph van Kool from EuroPace 2025 And I'll cite that reference. Because the precordial ECG leads are actually unipolar recordings, which I had kind of forgot, but they are, the steepest negative downslope of the QRS can be used to estimate local activation at that lead by moving Lead V5 to the V8 position at the inferior border of the left scapula on the back. That's over the posterior lateral LV wall. The negative derivative activation time in V8 was found to closely approximate the invasively measured posterior lateral QLV. Very high correlation and it was better than Lead V6. And it was present in patients with bundle branch block, left bundle branch block, and even in right bundle branch block, which they wrote in a research letter. So this provides a patient-specific reference before the lead is implanted. During implantation, the QLV from each pole of the quadrupole lead can be compared with this negative derivative activation in V8. And if that QLV approaches the measurement in Lead V8, then we know that we have reached the patient's posterior lateral electrical delay. And if it falls substantially short, we have not.