Symphony to Leadless pacing – An Ode to Joy
Hassan Khan1, Larry A Chinitz1*
1Leon H. Charney Division of Cardiology. New York
University Langone Health. New York, NY, USA
*Larry A Chinitz MD, FACC, FACP
Benjamin and Coyle Family
Professor of Medicine and Cardiac Electrophysiology
Director, Cardiac Electrophysiology and the NYU Heart Rhythm Center
Clinical Director, Leon H Charney Division of Cardiology
NYU School of Medicine
212-263-7149 (O)
larry.chinitz@nyumc.org
Word count, text: 1222 (excluding references)
Number of tables/figures: 1
COI; L.Chinitz- Speakers Honoraria; Medtronic,Abbott
Coi; H. Khan- None
Ludwig van Beethoven’s 9th Symphony is regarded by many musicologists as
one of the finest works in the history of music. It is notable for
several reasons, particularly being the first example of a composer
using voices, with words sung by a chorus and vocal soloist in the final
movement. These words were adapted from the poem
”Ode to Joy”, written
by Friedrich
Schiller, and to date symbolize the celebration of music, making all
who hear it feel better about life.
Leadless pacing has also made a transformational effect on the lives of
patients with bradyarrhythmias. Introduced to overcome the complications
and adverse effects associated with conventional transvenous pacemakers,
leadless pacing is observed to be safe, with a low risk of both short
and long-term adverse events and high rates of successful
implantation1, 2. To further the role of leadless
pacing, the MARVEL (Micra Atrial TRacking Using a Ventricular
AccELerometer) 23 prospective non-randomized
multicenter clinical trial, tested the ability of an enhanced AV
synchronous pacing algorithm utilizing the device’s three axis
accelerometer, to attain mechanical sensing of atrial contractility. The
MICRA AV TPS (Medtronic, MN) was released in 2020 with a ventricular
pacing and atrial tracking mode (VDD), and achieved mechanical atrial
sensing resulting in AV-synchronous pacing of >70% at rest
in 95% participants (38 of the 40 with complete heart block) within the
trial. Significant benefits to AV synchrony include avoidance of
pacemaker syndrome, improvement of quality of life and as seen in these
patients, improvement in left ventricle stroke volume and
function3-5.
The study observed that AV synchrony varied with physical activity and
posture, with best results achieved at rest. Patient selection is
crucial for optimal use of this algorithm as it is difficult to track
atrial rates >105 bpm. At higher sinus rates, i.e. during
exercise, the A3 and A4 signals fuse, along with encroachment of A4 on
PVAB as the sinus rate increases further. Patient characteristics remain
crucial and as seen in a subsidiary analysis of the MARVEL 2,
individuals with markers of diastolic dysfunction (higher E/A ratios)
and /or atrial myopathy (atrial strain) were found to be at higher risk
of reduced mechanical atrial sensing of A46. Moreover,
those with weak atrial contractions may not provide adequate A4 signals
to the accelerometer. Therefore, performances of the algorithm in a
real-world setting may not mirror those seen in the clinical trial
arena. Further complicating the issue remains the ideal threshold for AV
synchrony, which is assigned to >70% in research studies.
In practice however, the AV synchrony cut-off required to achieve
meaningful clinical benefit, avoid pacemaker syndrome and improve
quality of life remains uncertain, though is certainly not 100%
Recognizing that optimal AV synchrony in routine clinical practice may
be challenging, Kowgli et al. in this issue of the Journal
of Cardiovascular Electrophysiology , describe their multicenter
institutional experience of outpatient programming optimization of the
AV-synchronous MICRA leadless pacing system7. They
included 43 patients with MICRA AV following exclusion of those with
persistent atrial fibrillation or reduced follow-up. They describe the
frequency of AV synchrony (defined as the ratio of atrial mechanically
sensed (AM)-ventricular pacing to total ventricular paced percentage) at
device interrogation done at 3 months of follow up. They report an
overall mean AV synchronous pacing (AsVP) of 62.9%. In 65% of the
patients adequate AV synchrony with AsVP >70% was found.
Those with inadequate AsVP (<70%) had a higher body mass
index, higher prevalence of congestive heart failure and prior history
of cardiac surgery. Authors note that a small A4-wave amplitude, high
ventricular pacing burden, and inadequate device reprogramming (over-use
of auto A4 threshold, or lack of initiation of VDD mode at
initialization) were main considerations for suboptimal AV synchronous
pacing.
Most importantly, their data confirms and is in line with recent
reports,8, 9 that the success in achieving AV
synchrony in a real-world setting may be lower than the MARVEL 2
clinical trial. The results also emphasize the importance of active
programming changes which can significantly improve AV synchrony
following an optimization post implantation. As identified in this
report, MICRA AV optimization may require a learning curve, noted by an
improvement in AsVP from 55% earlier, to 68% later in the study.
Critical programming changes made by performing a manual atrial
mechanical (MAM) test while disabling the features that automatically
affect these, include adjusting the post ventricular atrial blanking
(PVAB), A3/A4 windows and A3/A4 thresholds, and turning off the AV
conduction mode (VVI +) in those with complete heart block and escape
>40 bpm. The authors and others8, 9 have
identified helpful examples of troubleshooting these interval timings
and thresholds for optimizing AV synchrony, which an implanter must be
familiar with in order to successfully manage patients with leadless AV
synchronous devices. Critically, while performing a MAM test, a key
prerequisite for successful interpretation of device tracings is the
inclusion of an optimal ECG tracing. In cases where standard leads do
not show a discernable P wave, the Lewis lead method can be
helpful10. Several key steps towards successful
optimization of AV synchrony are summarized in Figure 1.
Kowgli et al. evaluated AV synchrony at device interrogation 3 months
post implant whereas MARVEL 2 limited the analysis duration to about 30
minutes immediately after pacemaker optimization. This is a somewhat
artificial setting and would be expected to be different from
observations made at 3 months and longer periods of follow-up. Real
world settings are also associated with changes in heart rate, patient
movement, atrial or ventricular arrhythmias, as well as changes in
lifestyle and medications. Therefore, an optimization session both at
post-op (prior to discharge) and in the clinic at follow-up, with prior
Holter monitoring and exercise testing in younger patients, may help
detect AV dysynchrony earlier and allow recognition and correction of
atrial mechanical under or oversensing.
The current study acknowledges the complexity of leadless pacing and the
need for optimization at follow-up to achieve higher levels of AV
synchrony. It also reflects on patient selection being crucial to reap
the full benefits of leadless technology. In patients with fast baseline
sinus rates, in younger and physically active patients, or those who may
have a greater reliance on AV synchrony at peak heart rates, this device
may not be optimal. In addition, P wave amplitude, frequent atrial and
ventricular arrhythmias, and sinus bradycardia will adversely affect the
ability to achieve AV Synchrony. With appropriate patient selection,
monitoring and best practices of device programming, leadless pacemakers
will undoubtedly achieve clinically relevant AV synchrony. The true
marvel of leadless technology can be seen as an impressive reduction in
complication rates and better patient satisfaction compared to current
transvenous devices. Further improvements in design, technology and best
practices will deliver symphony to pacing and afford those who use it an
experience that is safe and reminiscent of normal cardiovascular
physiology.