POST CRT OPTIMISATION

BALAKUMARAN. J
PGIMER & DR.R.M.L
HOSPITAL-NEWDELHI.
POST CRT - OPTIMISATION

INTRODUCTION
 CRT has been firmly established as a treatment for patients with symptomatic heart failure.
Several randomised controlled trials showed improvements in exercise capacity and quality
of life.
 Despite these advances, approximately 30% of patients who meet current criteria for
implantation of such a device do not show objective evidence of clinical benefit.
 Implantation of a CRT device is expensive, time consuming and involves some risk so it is
important to accurately identify patients who are likely to respond and to optimise
pacing ,lead placement and device programming to maximise the benefit in these
selected patients.
Heart 2005;91:1000–1002

Onset of biventricular pacing results in immediate improvements in cardiac function.
 increased peak rate of rise of intraventricular pressure.
 an increase in stroke volume , and
 higher systemic arterial blood pressure .
Longer-term effects include
 improvements in clinical outcome measures including exercise capacity,
 reductions in LV volumes,
 quality of life measures and NT-pro BNP .
Whinnett et al. BMC Cardiovascular Disorders 2014

Cause of non-responders to CRT
J Am Coll Cardiol. 2009;53(9):765-773
75 patients

Non-responders- will respond still
 Non-adherence to medications
 Inappropriate medications.
 Pre-renal azotemia
 Recurrent ischemia
 Adequate Vent. rate control in AF .
 Severe MR
 Inappropriate settings
 Failure to capture(lead dislodgement)

Initial Problems
 Inability to cannulate the CS=1-5%
 CS anatomy not good in 20%
 Tortousity of CS .
 Scarred LV-problem with high threshold.

CRT –Response vs Non-response

Viability of myocardium
 When heart failure is ischaemic, viability of LV myocardium is likely to be a
crucial determinant of the response to CRT and patients with extensive LV
scarring ------ unlikely to benefit.
 Present practice does not generally include an assessment of LV viability
before CRT and further studies are required to determine the role of such
assessments in patient selection.
 Response poor to CRT when a posterolateral scar is present.

Optimal left ventricular lead position
 Varies between patients and is likely to be driven by multiple factors, such as
venous anatomy, regional and global LV mechanical function, myocardial
substrate, characterization of electrical delay, and other factors.
 The success of resynchronization depends on pacing from a site that causes a
change in the sequence of ventricular activation that translates to an
improvement in cardiac performance.
Lateral free wall –Best response (latest to be activated and stimulation at these
sites reliably restores homogenous LV activation).

Predictors of positive response to cardiac resynchronization
therapy.
 82 patients.
Smaller left ventricular end diastolic and end systolic diameters
lower serum uric acid concentration
Associated with better response to CRT.
LVEDD and non-ischemic HF etiology were the strongest independent predictors
of positive response to CRT.
Females- better response
BMC Cardiovascular Disorders. 2014; 14;55

ECG- STEPS FOR OPTIMAL LV SITES
 Positive QRS in lead V1 during LV pacing –free wall in LV (R, Rs,RS)
 Superior axis- inferior LV lead postion.
and inferior QRS axis -anterior LV lead position.
 Lead aVF differentiates between LV lead positions in the circumferential
direction.
 Lead aVF is expected to differentiate between a more inferolateral (negative
aVF) and anterolateral position (positive aVF).
 Isoelectric QRS pattern in aVF is suggestive of a true lateral LV lead position
Journal of Electrocardiology xx (2014) ARTICLE IN PRESS

Basal vs mid vs apical
 Positive precordial QRS concordance during LV pacing - a basal LV lead position.
 QRS transition pattern in V4–V6 - a mid-level LV lead position.
 QRS transition pattern earlier than V4 - an apical LV lead position
 A qR or Qr complex in lead I is present in 90% of cases of biventricular pacing

Cardiology Journal 2011, Vol. 18, No. 5
RV APEX- LEFT INFERIOR
RVOT-RIGHT INFERIOR
LV-RIGHT INFERIOR
RVA + LV –RIGHT
SUPERIOR
RVOT+ LV- RIGHT
INFERIOR

LIMITATIONS
However, several factors potentially limit the ability of the electrocardiographic QRS
pattern to identify the precise LV lead position
 Presence and location of myocardial infarction or fibrosis, shape and size of the
heart,
 Position of the heart within the thorax,
 Incorrect ECG electrode placement.

AV / VA OPTIMISATION
AV interval optimization
-Adjusts contraction sequence between LA and LV to optimize LV filling
without truncating atrial contraction
VV interval optimization
– Adjusts contraction sequence between the left and right ventricles to
produce the largest stroke volume

AV/ VV OPTIMISATION
 There are multiple strategies for AV and VV optimization without a clear ‘‘gold
standard’’ for comparison, which makes interpretation of available data
challenging.
 Guidelines for CRT also do not provide recommendations for optimization of these
parameters, reflecting a lack of consensus on this issue.
 Despite these limitations, AV and VV optimization may prove useful in select
patients with CRT, and a working understanding of the methods and controversies
involved is important for all cardiologists who manage these patients.

AV Optimisation
 Optimal AV delay
Derived from dp / dt using PR and QRS.
QRS > 150ms= 0.7 x PR -55
QRS < 150 ms = 0.7 X PR

AV-delay optimization using the
biventricular-paced ECG
 Role of optimizing the AV delay and VV interval is to create the best possible
electrical resynchronization.
 The best AV delay and VV-interval programming requires knowing the onset of
intrinsic ventricular activation.
 To ensure 100% capture of LV pacing, the AV delay in CRT should preferably be
programmed to a value shorter than the onset of intrinsic ventricular activation,
since exercise fastens intrinsic AV conduction time
Journal of Electrocardiology xx (2014) ARTICLE IN PRESS

 Stepwise increase of the AV delay during simultaneous BiV pacing
starting with a short AV delay, the onset can be identified as the AV
delay where the QRS morphology changes .

VV-interval optimization using the
biventricular-paced ECG
Pre-excitation of the LV can allow fusion of the activation wave derived from the
right bundle branch with that from the LV pacing lead, which may provide more
pronounced hemodynamic improvement than simultaneous BiV pacing.
As a consequence, programming of the VV interval should be used to create a QRS
complex with adequate contribution from LV pacing containing a dominant R (R, Rs
or RS pattern) in lead V1–V2.
V1- R, Rs, RS

Guide for CRT evaluation and optimization using the 12-lead ECG in daily
clinical practice

AV Optimisation
Echocardiography
 Ritter method
 Meluzin method
 Iterative method
 Ishikawa method
 Maximal filling time -Mitral VTI
 Aortic VTI , LV dp/dt
 Myocardial performance test.
ECG
Impedance cardiography
Finger plethysmography
Device algorithms
 Peak endocardial acceleration
 AV EGM-based algorithm
Diastolic
timing
Systolic
function

Optimizing LV diastolic filling
.
Mitral inflow is dependent on timing of both left atrial and left ventricular
systole, and interatrial and interventricular conduction delays will affect optimal
timing of ventricular pacing.
AV delay optimization based on LV diastolic function utilizes the filling pattern
obtained through Doppler echocardiography of mitral inflow, and several
different methods have been used and evaluated.

RITTERS METHOD.
This method was originally proposed for patients with complete heart block .
The MIRACLE trial optimized the AV interval with this method.
.
Measure the time from onset of QRS complex to time of termination of the A-wave
(QA interval) is measured at both a long (AVlong) and a short AV delays (AVshort).
The optimal AV delay is calculated from following formula:
AVopt = AV long - (QA short – QA long).

Ritters method
The interval from the pacing spike to the end of the A wave on mitral inflow is measured at short and
long AV delays. The difference in these time intervals is then subtracted from the long AV delay to
calculate the optimal AV delay.

ITERATIVE METHOD
 The iterative method is the most common echocardiographic optimization
technique.
 Used in the CARE-HF and the SMART-AV trials.
 More recently, the reproducibility and consistency of measurement of this
technique has been challenged despite its relative ease of use compared
with other techniques

1. Measure the intrinsic PR interval hence to program AV delay to as
shorter value.
2. PW of mitral valve. Record E and A waves.
3. Shorten the AV delay to 20 ms and record the wave forms.
4. See that A waveform is cut short-i.e truncated.
5. Once it is truncated increase delay by 10 ms.
6. AV delay- E and A wave forms are separate and no A wave cut off.

Iterative method
AV delays that are either too short (A) or too long (C) will result in truncation of the A wave of mitral inflow or E and A
wave fusion, respectively. At the optimal AV delay, E and A wave separation results in maximum diastolic filling time
without truncation of the A wave

 If patient has good underlying atrial rhythm optimise sensed AV delay.
 If requires atrial pacing, optimise paced AV interval.
 Some patients will fall in between, hence optimise both and keep sensed AV delay 30 ms
shorter than paced AV delay.

LVOT VTI METHOD
 LVOT pulsed-wave Doppler velocity time integral (VTI) correlate with LV
stroke volume .
 Using this method, LVOT VTI is measured over a range of AV delays, and the
AV delay resulting in the greatest increase in VTI is chosen as the optimal AV
delay .
 AV intervals longer when calculated using the LVOT VTI method than with
the Ritter method.
Fast sweep
Large velocity scale
Low filter

LVOT VTI METHOD
AV delay optimized to achieve the maximum stroke volume based on the aortic
outflow tract VTI. In this case, the VTI increased from 16 to 23 cm with an
increase in the AV delay from 80 to 150 ms.

 Two small, nonrandomized comparisons of LVOT VTI method vs. the
Ritter method of mitral inflow- VTI better.
 LVOT VTI vs fixed delay (40 patients)
Patients optimized using LVOT VTI experienced greater 3-month
improvement in NYHA class and quality of life. Importantly, they also
reported stable optimal AV delays over time.
Heart Rhythm 2004;1:562–7.

MITRAL FLOW VTI
 Mitral inflow VTI is another method of Doppler optimization.
 30 patients POST - CRT implantation.
Based on the maximal increase in invasively measured left ventricular dP/dt vs
Mitral flow VTI, the iterative method, aortic VTI, and Ritter formula.
 Mitral inflow VTI correlated best with the maximal increase in dP/dt (29 of 30
patients).
Am J Cardiol 2006;97:552–7

Simplified Mitral Inflow Method ( Meluzin)
 A long AV interval is programmed and the delay between the end of
the A wave and the onset of mitral regurgitation (MR) is measured
(t) of mitral regurgitation (MR) is measured (t).
 This value is then subtracted from long AV interval yielding the
optimal AV interval interval, yielding the optimal AV interval.
 This approach relies on the presence of MR, which is a significant
limitation.
Meluzin et al. PACE 2004;27:58-64

DIASTOLIC MR (ISHIKAWA METHOD)
 This method aims to minimize diastolic MR.
 A long AV delay is selected to induce diastolic MR.
 The optimal AV delay is calculated by subtracting the duration of AE time
from the initial long AV delay.

LV dp/dt
 The measurement of the LV dP/dt max provides information on LV
contractility.
 Non-invasive measurement of this parameter is performed on the
continuous-wave Doppler spectral signal of the mitral regurgitation.
 First, the time difference between two points of the spectral signal is
measured (usually between 1 and 3 m/s time points). Then, the pressure
gradient between these two points is calculated according to Bernoulli
equation.
 The optimal AV interval corresponds to the highest value of LV dP/dtmax

Myocardial performance index (MPI)
 The measurement of the myocardial performance index may be a useful
method to optimize the AV interval.
 The myocardial performance index is a comprehensive measurement of
LV function. This index is calculated as the sum of isovolumic contraction
and relaxation times divided by the ejection time .
 The optimal AV interval is defined by the lowest myocardial performance
index.

Other methods of AV optimization
The above methods for AV delay optimization all rely on echocardiography.
While this has been the ‘‘gold standard’’ for AV delay optimization, it
requires significant training, skill, time, and healthcare resources. As a result,
noninvasive tools have been developed.
1. Noninvasive measures of hemodynamic optimization
2. Device-based intracardiac electrogram (IEGM) algorithms.

IMPEDENCE CARDIOGRAPHY
 Impedance cardiography (IC) uses changes in transthoracic impedance to estimate stroke
volume.
 A low amplitude (1mA) high frequency (100KHz) current is delivered via three surface
electrodes placed behind the neck and bilaterally on the lower chest while the resistance to
this current flow is measured by four other electrodes placed on each side of the sternum and
on the abdomen.
 The rationale is that changes in thoracic impedance are caused by the systolic aortic flow and
on this basis the system calculates stroke volume and CO on a beat-to-beat basis from the
TIC signal.
J Interv Card Electrophysiol 2005;13:223–9

FINGER PLETHYSMOGRAPHY
 FFPG allows measurement of changes in peripheral pulse pressure- correlate
reasonably with measured central aortic pressure.
 Optimal AV delay, defined as that producing the greatest change in pulse
pressure, was identical using either FFPG or central aortic pressure. Similarly,
the Finometer® (Finapres Medical Systems, Amsterdam, Holland) is a device
that provides continuous, noninvasive measurement of arterial pressure
through a finger cuff photoelectric plethysomgraph.
Europace2006;8:358–66.

BMC Cardiovascular Disorders 2014, 14:42

Peak endocardial acceleration (PEA)
Peak endocardial acceleration (PEA) is a device-based algorithm makes use of an
accelerometer incorporated into a pacing lead behind the pacing electrode.
It has been shown to correlate well with the optimal AV delay by the Ritter method.
The CLEAR trial randomized 238 patients with CRT to PEA optimized AV/VV
intervals or to “usual” optimization methods. At one-year follow-up, response to CRT
was significantly higher in the group optimized by PEA (76 vs. 62%), although this
benefit was largely restricted to improvements in subjective endpoints
Europace 2012;14:1324–33.

Automatic Optimization of Cardiac Resynchronization Therapy Using SonR—Rationale and
Design of the Clinical Trial of the SonRtip Lead and Automatic AV-VV Optimization Algorithm
in the Paradym RF SonR CRT-D (RESPOND CRT) Trial
 The SonR system uses an accelerometer sealed in a right atrial lead (the SonRtip
lead, Sorin Group Italia, Saluggia, Italy) to measure the SonR signal. The SonR
sensor is based on the measurement of vibrations generated by the heart cycle.
 The peak-to-peak amplitude of the myocardial vibrations generated during the
isovolumetric contraction phase (SonR signal) is correlated to the first heart sound
amplitude, itself correlated to cardiac contractility. Previous studies demonstrated
that changes in the SonR signal amplitude correlate closely with changes in
invasive LV dP/dtmax..
Am Heart J. 2014 Apr ;167(4):429-36

Acoustic cardiography
 Acoustic cardiography is another relatively new technique for AV optimization.
This technology integrates the surface electrocardiogram and heart sound data to
measure the intensity of S3, the electromechanical activation time (EMAT,
representing the time from the QRS onset to S1), and LV systolic time (LVST, the
time interval from S1 to S2).
 Changes in each parameter can indicate worsening heart failure: an increase in S3
suggestive of increased left ventricular filling pressure, prolongation of EMAT
indicative of reduced LV contractility, and a reduced LVST suggestive of reduced
systolic function. This was comparable to the mitral inflow method.
Congest Heart Fail 2006;12(Suppl 1):25–31.

Intracardiac electrogram-based AV optimization
 IEGM-based AV delay algorithms are clearly desirable given the potential
for incorporation into device software for rapid optimization and
potentially continuous modification.
 Such technology could reduce costs, time, and the possibility of user error
introduced with more complex methods such as echocardiography.
St.Jude- QUICK OPT
Boston-SMART DELAY.
Medtronic-ADAPTIVE

Areas of uncertainty in AV optimization
 It is evident that many issues regarding AV delay optimization remain unresolved.
 While the majority of the landmark trials of CRT incorporated some form of AV delay
optimization at the time of implantation, definitive data supporting their superiority over an
empiric, fixed AV delay are lacking.
 Most available data involve hemodynamic studies demonstrating an acute improvement with
optimization.
 The majority of studies report the acute hemodynamic effects of the optimal AV delay at implant
or shortly thereafter, with few evaluating the long-term stability of the optimized AV delay.
J Am Coll Cardiol 2009;53:765–73.

VV optimization
 AV delay optimisation to ensure optimal LV diastolic filling and systolic
function is complex.
 These issues are even more apparent in studies of VV optimization.
 The landmark trials of CRT in heart failure demonstrated a benefit of CRT
using simultaneous Bi V pacing in conjunction with AV delay optimization
.

 VV Interval Optimization
Electrocardiogaphy
Echocardiography
– M mode
– LV outflow VTI
–Dyssynchrony assessment
– 3D echocardiography
LV dp/dt
Finger plethysmography
Device algorithms

LVOT VTI
 The echocardiographic method based on the assessment of LV systolic
performance (LVOT VTI) has been discussed in the AV interval optimization
section. Similarly, the largest LVOT VTI defines the optimal VV interval.
 The product of the LVOT cross-sectional area and VTI measured on the pulsed- or
continuous wave Doppler recordings of the LVOT or aortic valve yields the stroke
volume.
 The optimal AV interval is defined by the largest stroke volume.

 Optimize the sensed and paced AV delays. Measure the VTI while adjusting the
interventricular settings.
 Do LV first and measure VTI values for 20, 40, 60 and 80ms.
 Record the off set value that produces the greatest VTI value.
 Repeat with the RV but this time, adjust the AV delay.
 To adjust the A Vdelay, subtract the interventricular delay from the AVdelay.
 Record the VTI scores.
 Optimal VV timing delay is the one that produces the greatest VTI value.

Invasive left ventricular dP/dtmax
 A pressure sensor-tipped wire is inserted into the LV through a cardiac
catheter. The maximal pressure change per unit of time (dP/dtmax) is
considered a reliable method of assessing LV systolic function.
 Disadvantages include the invasive nature of the procedure, limited
repeatability, time required, and cost of equipment.
 No long-term follow-up or clinical outcomes
were included

Dyssynchrony assessment
 Interventricular dyssynchrony (difference between aortic and pulmonary pre-
ejection times)
 Time to peak systolic velocity at TDI (time difference between two or four
opposing walls, standard deviation of 12 LV segments)
 Speckle-tracking echocardiography (radial, longitudinal and circumferential
dyssynchrony)
 Real time 3D echocardiography (systolic dyssynchrony index)

Dyssynchrony assessment
 VV dyssynchrony is assessed by the difference between the left and right pre-ejection time
measured with pulsed-wave Doppler echocardiography at LVOT and right ventricular
outflow tract, respectively.
 Intra-LV dyssynchrony mainly measured with TDI is also used as effective means of
guiding VV interval optimization.
 The time difference between peak systolic velocity of two or four opposing walls or the
standard deviation of time to peak systolic velocity of 12 LV segments are the most common
methods to measure intra-LV dyssynchrony.
 In addition, speckle tracking echocardiography and real time 3-dimensional
echocardiography are valuable novel techniques for intra-LV dyssynchrony assessment but
so far no studies investigated the role of these techniques for VV interval optimization.

 VV optimization using echocardiographically derived markers of
dyssynchrony is significantly limited by the time and expertise
required.
 Thus, the applicability of dyssynchrony optimization in a “real-
world” clinical setting is questionable.

Other methods of VV optimization
Despite limited data demonstrating improved outcomes with
echocardiography-guided VV optimization, several other approaches
have been developed.
These include real-time intracardiac echocardiography during CRT
implantation , electroanatomic mapping , radionuclide angiography ,
the Finometer, peak endocardial acceleration , and optimization using
the surface QRS and . Several device-based IEGM algorithms for VV
optimization have also been developed and evaluated.

VV Optimisation - Limitations
 The methods used for VV optimization may be suboptimal to achieve
adequate inter- and intra-ventricular resynchronization. In almost all
studies of VV optimization, AV delay optimization was performed first
followed by VV optimization.
 Magnitude of hemodynamic improvement with optimized VV pacing may
be too small to be clinically meaningful.
 It is has been repeatedly shown that the optimal VV delay, like the AV
delay, varies over time.

Which interval is first?
 A recurrent question that was never completely addressed in the various studies, is
whether AV optimization should be followed by VV optimization or vice versa (or
even simultaneously).
 Indeed, performing this procedure in different order not necessarily produces the
same results.
 The common clinical practice is to optimize the AV interval first, followed by VV
optimization; in all studies, AV and VV intervals were optimized separately. It
could be possible, however, that a method that permits simultaneous optimization
of the AV and VV intervals may provide additional haemodynamic benefits.

DEVICE BASED ALGORITHMS
 QuickOpt™ is an intracardiac electrogram (IEGM)-guided timing cycle optimization
algorithm incorporated in St Jude Medical CRT is a quick (can be performed in 2 min)
and easy to use technique that aims to determine optimal AV and VV intervals automatically.
 The optimal sensed AV interval is calculated based on the atrial IEGM. The atrial IEGM (P-
wave duration) represents the sum of right and left atrial activation (atrial conduction time).
 The algorithm measures the width of the atrial intrinsic depolarization (atrial IEGM) and
adds an off-set factor ( 30 or 60 ms) which enables delivery of ventricular pacing after the
completion of atrial electrical activation and atrial mechanical contraction, thus ensuring
complete mitral valve closure and maximizing preload.

Paced AV delay = sensed + 50 ms

 The VV offset determination is more complex.
 The optimal VV interval is calculated based on the intrinsic and paced conduction
properties of the ventricles, which are characterized by performing sensed and
paced (RV and LV) tests.
 The time interval between sensed local activation between the RV and
LV leads is first measured (DELTA). The difference in conduction delay
to the RV lead during LV pacing and LV lead during RV pacing is then
calculated (e).
 The estimated optimal VV offset is then given VV = 0.5 X (DELTA + e), with
positive values indicating left ventricular preactivation and negative values
indicating right ventricular preactivation.
Freedom trial-no benefit

QUICK OPT vs ECHO opt- inferior

AV Optimization – SmartDelayTM (BOSTON)
Developed through intraoperative measurements and validated with invasively measured LV
dP/Dt. Uses intrinsic AV intervals and the duration of native VV conduction time to calculate the
optimal delay.
Adjusted for LV lead location
Separate calculations for sensed and paced AV delays
Keeps the AV delay to between 50 ms and 70% of the intrinsic AV interval
The optimal VV delay is estimated using the formula VV=0.33×(RV−LV electrical delay)-20 ms

SMART-AV TRIAL
Fixed AV delay vs Iterative vs Smart delay algorithm
980 patients.
Intrinsic intervals (As-Vs,Ap-Vs )
Interventricular timing(RVs-LVs interval)
LV lead location
No difference .

ADAPTIVE (MEDTRONIC)
 A third IEGM-based algorithm developed by Medtronic (Medtronic, Inc.,
Minneapolis, Minnesota, USA) was recently evaluated in the Adaptive
CRT trial.
 The algorithm provides continuous adjustment of the AV and VV intervals
based on periodic measurement of the intrinsic AV interval (as measured
from the RA and RV electrodes), the interval from the sensed atrial EGM
to the end of a far-field P wave, and the interval from sensed RV EGM to
the end of a far-field QRS complex.
Am Heart J 2012;163(747-52):e1.

 If the intrinsic AV interval is <200 ms and the heart rate is <100 bpm,
LV-only pacing is provided at an AV delay prior to intrinsic
conduction by >40 ms.
 If the intrinsic AV interval is >200 ms or the heart rate >100 bpm, BiV
pacing is provided at an AV delay such that >50 ms prior to the
intrinsic RV sensed EGM.
 The VV offset is then determined based on the intrinsic AV delay and
interval from the sensed RV EGM to the end of the QRS complex

 LV only pacing is preferred over BiV pacing when A-to-RV conduction is
normal
 Results in similar or superior LV function and is also associated with
improved RV function vs. BiV pacing.
 Timing of LV pace critical to achieving benefit.
 Higher % BiV pacing if AV delay is adjusted to pace in advance of
intrinsic QRS
 Better LV hemodynamics if VV delay is adjusted to promote intrinsic RV
activation when it is sufficiently preserved
Journal of Arrhythmia 29 (2013) 153–161

 For patients with normal AV conduction, Adaptive CRT showed an increase in
CRT response rate of 12 % at six months.
 21 % reduction in heart failure hospitalizations as compared to historical CRT
trials.
 46 % reduced risk of AF, and a 61 percent lower risk of AF-related problems.
 47 % reduction in 30-day hospital readmissions for heart failure.
Heart Rhythm. September 2013;10(9):1368-1374.

SUMMARY – AV/VV OPTIMISATION

TRIALS IN OPTIMISATION
MORE-CRT trial-ST.jude using quadripolar leads (quartet)-decreased intraop and post.op
lead related compl.

CONCLUSION
 Many different methods for AV and VV delay optimization have been developed, and all
have demonstrated that optimized delays, regardless of the method, result in acute
improvements in LV diastolic and systolic function.
 These functional improvements have unfortunately not consistently translated into
improvements in clinical outcomes or response rates to CRT. As routine AV delay
optimization was performed in most trials demonstrating efficacy of CRT, it is a reasonable
strategy that does not appear to be harmful.
 At the present time, the benefit of routine use of AV and VV interval optimization is unclear
and may be most useful in the population of CRT ‘‘non-responders,’’although the benefit of
this strategy also requires further study. (In our setting, Echo optimisation can be done-
once in 3months)

Rate adaptive AV delay ?
 Rate-adaptive AV delay shortening algorithms are a universal feature in modern dual
chamber pacing systems due to improvements in exercise capacity with their use , although
the utility of such an algorithm in CRT devices is controversial.
 One study of 36 patients determined the optimal AV delay during rapid atrial pacing and
following exercise using the aortic VTI method. The optimal AV delay by VTI was
paradoxically longer at faster heart rates .
 Rafie et al. found that the optimal AV delay was shorter at higher atrial pacing rates –hence
better.
 Shanmugam et al. Performed using the iterative method in 52 patients at rest and with
exercise and found that the optimal AV delay was shorter at higher heart rates-better-
resulted in significantly longer exercise times and higher peak oxygen consumption.

CRT (Future)
 Left ventricular lead placement can have inherent difficulties based on coronary venous anatomy and thus may
limit optimum placement. Utilisation of a single intramyocardial lead at the atrioventricular septum does not
require access of the coronary sinus, nor does the lead invade the left ventricle
(Noheria A et al, J Cardiovasc Electrophysiol 2013; 24:1–6).
 Investigational studies have shown that the atrioventricular septum is an ideal target to electrically stimulate a
synchronised contraction of the left ventricle
(Konecny T et al, Cardiovascular Revascularization Medicine 2013;14:137–138).
 Reiterations of this novel and patented lead design by altering the co-axial, parallel, and longitudinal designs of
the bi-helical inner and outer electrodes surrounding an insulated central pin have shown improved performance.
More recently, this novel lead has shown safety, durability, and efficacy in pacing from the atrioventricular
septum in chronic canine studies.

POST CRT OPTIMISATION

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