CRT
BIV PPM in the guidelines

Kindermann HOBIPACE
A prospective randomized trial published in 2006 concerning patients with LV enlargement, LVEF less than
or equal to 40%, and conventional indications for pacing showed that biventricular pacing was associated
with improved functional class, exercise capacity, LVEF, and serum brain natriuretic peptide levels
compared with RV pacing  


Baker CM, Christopher TJ, Smith PF, Langberg JJ, Delurgio DB, Leon AR. Addition of a left ventricular lead to conventional pacing systems
in patients with congestive heart failure: feasibility, safety, and early results in 60 consecutive patients. Pacing Clin Electrophysiol. 2002;
25: 1166–71.
It has also been demonstrated that LV dysfunction in the setting of chronic RV pacing, and possibly as a
result of RV pacing, can be improved with an upgrade to biventricular pacing


Doshi RN, Daoud EG, Fellows C, et al. Left ventricular-based cardiac stimulation post AV nodal ablation evaluation (the PAVE study). J
Cardiovasc Electrophysiol. 2005;16:1160 –5.
Among patients undergoing AV junction ablation for chronic AF, the PAVE (Left Ventricular-Based Cardiac
Stimulation Post AV Nodal Ablation Evaluation) trial prospectively randomized patients between RVA pacing
and biventricular pacing.


-Leon AR, Greenberg JM, Kanuru N, et al. Cardiac resynchronization in patients with congestive heart failure and chronic atrial fibrillation:
effect of upgrading to biventricular pacing after chronic right  ventricular pacing. J Am Coll Cardiol. 2002;39:1258–63.
-Valls-Bertault V, Fatemi M, Gilard M, Pennec PY, Etienne Y, Blanc JJ. Assessment of upgrading to biventricular pacing in patients with
right ventricular pacing and congestive heart failure after atrioventricular junctional ablation for chronic atrial fibrillation. Europace. 2004;6:
438–43.
The patients with RVA pacing had deterioration in LVEF that was avoided by the patients with biventricular
pacing. The group with biventricular pacing also had improved exercise capacity compared with the group
with right apical pacing. The advantages of biventricular pacing were seen predominantly among patients
with reduced LVEF or heart failure at baseline. Other studies have shown that among AF patients who
experience heart failure after AV junction ablation and RV pacing, an upgrade to biventricular pacing results
in improved symptomatology and improved LV function.


-de Cock CC, Meyer A, Kamp O, Visser CA. Hemodynamic benefits of right ventricular outflow tract pacing: comparison with right
ventricular apex pacing. Pacing Clin Electrophysiol. 1998;21:536–41.
-Tse HF, Yu C, Wong KK, et al. Functional abnormalities in patients with permanent right ventricular pacing: the effect of sites of electrical
stimulation. J Am Coll Cardiol. 2002;40:1451– 8.
patients with preserved LV function requiring ventricular pacing would benefit from initial implantation with a
biventricular device (or one with RV pacing at a site with more synchronous ventricular activation than at the
RV apex, such as pacing at the RV septum, the RV outflow tract


-Occhetta E, Bortnik M, Magnani A, et al. Prevention of ventricular desynchronization by permanent para-Hisian pacing after
atrioventricular node ablation in chronic atrial fibrillation: a crossover, blinded, randomized study versus apical right ventricular pacing. J
Am Coll Cardiol. 2006;47:1938–45
or the area of the his bundle.


-Nahlawi M, Waligora M, Spies SM, Bonow RO, Kadish AH, Goldberger JJ. Left ventricular function during and after right ventricular pacing. J Am
Coll Cardiol. 2004;44:1883– 8.
-Tantengco MV, Thomas RL, Karpawich PP. Left ventricular dysfunction after long-term right ventricular apical pacing in the young. J Am
Coll Cardiol. 2001;37:2093–100.
Some patients with normal baseline LV function experience deterioration in LVEF after chronic RV pacing


-Tantengco MV, Thomas RL, Karpawich PP. Left ventricular dysfunction after long-term right ventricular apical pacing in the young. J Am
Coll Cardiol. 2001;37:2093–100.
-Karpawich PP, Rabah R, Haas JE. Altered cardiac histology following apical right ventricular pacing in patients with congenital
atrioventricular block. Pacing Clin Electrophysiol. 1999;22:1372–7.
-Thambo JB, Bordachar P, Garrigue S, et al. Detrimental ventricular remodeling in patients with congenital complete heart block and
chronic right ventricular apical pacing. Circulation. 2004;110:3766 –72.
Studies have suggested that chronic RVA pacing in young patients, primarily those with congenital complete
heart block, can lead to adverse histological changes, LV dilation, and LV dysfunction.


-Bristow MR, Saxon LA, Boehmer J, et al. Cardiac-resynchronization therapy with or without an implantable defibrillator in advanced
chronic heart failure. N Engl J Med. 2004;350:2140 –50.
-Cleland JG, Daubert JC, Erdmann E, et al. The effect of cardiac resynchronization on morbidity and mortality in heart failure. N Engl J Med.
2005;352:1539–49.
There is a role for CRT-P in some patients, especially those who wish to enhance their QOL without
defibrillation backup. Elderly patients with important comorbidities are such individuals. Notably, there is an
important survival benefit from CRT-P alone.


PACE (pacing to Avoid Cardiac Enlargement) - Chinese University of Hong Kong - Cheuk Man Yu -
NEJM 2009; 3-61
RV apical pacing decreases EF in patients with normal LV function (45%) and standard indications for
pacing (SND, Brady 2/2 AVB), regardless of diastolic function.
Randomized 177 patients to RVP vs BIV P, starting at a normal EF
At 12 months EF was lower in RVP group than BIV group (54.8%±9.1% vs 62.2±7%, p<0.001)

MADIT CRT Apical vs Basal - Arthur moss, Circulation 2011
To analyze the impact of the LV lead position in 799 patients followed for 29±11 months. Only the apical
lead position was associated to higher rates of heart failure (HR 1.72, 1.09 to 2.71, p=0.019) and death (HR
2.91, 1.42 to 5.97, p=0.004)

LV lead placement in CRT: where and how? Fakhar Khan Europace 2009 (LR)
Up to 30% of patients do not attain clinical benefit for CRT. This is a review of 58 references on the best site
to implant he LV lead, goes through the speckle literature, echo, MRI, and the impact of scar burden by
going through the major studies. In conclusion, the relationship between localized scar, LV dyssynchrony,
and LV lead tip position with respect to underlying scar and region of maximal delay is not
fully understood.

Early results of the QUAD lead - HR 2011 - Giovanni Forleo, Milan
22 patients were implanted either with the Quad lead vs 23 patients implanted with thre conventional bipolar
lead. Primary outcome was LV lead failure as defined by the need for lead revision or reprogramming for the
first 3 months after implantation. 2 lead dislodgements and 4 PNS were reported in the bipolar group vs.
only 1 PNS managed non invasively in the Quad group.

Clinical and procedural outcomes of patients implanted with a QUAD - Giovanni Forleo, Milan - HR
2012
Over the longer term, CRT with the quadripolar LV lead is associated with excellent pacing thresholds, low
rates of dislocations, and PNS.

LV pacing from the site fo late electrical activation improves HD in the QUAD - Carlo Pappone  -
APHRS 2012
BIV Pacing with LV Pacing at teh site of late electrical activation significantly improves hemodynamic
response in CRT, demonstrated using a pressure volume loop  during LVP with either the distal or the
proximal site of the QUAD SJM lead.

Substudy of the SMART AV trial. The relationship between electrical delay and LV remodelling with
CRT - Michael Gold - European Heart Journal 2011 (MUSC)
Multicenter prospectively designed study (MUSC, Cleveland Clinic OH, MGH, Viriginia Commonwealth MC
Richmond) looking at electrical delay QLV as the interval from the onset of the QRS from the surface ECG
to the first large peak of the LV EGM. Reverse remodeling response rates (>15% reduction in LVESV)
increased from 50 to 72%. Patients in the highest quartile of QLV had a 3.21 fold increase (1.58 to 6.50,
p<0.001) in their odds of a reverse remodelling response. Electrical dyssynchrony, as measured by QLV,
was strongly and independently associated with reverse remodelling and QOL with CR (QLV > 95 ms, The
QLV interval measured for every patient was reduced by 30 ms to account for the average variable latency
(or noise) between the alignment of surface ECG and the EGM channels in device programmers).

SMART-AV trial.
Stein KM. SmartDelay determined AV optimization: a comparison of AV delay methods used in cardiac resynchronization therapy (SMART-AV):
rationale and design. Pacing Clin Electrophysiol 2010;33:54–63.
Ellenbogen KA. Primary results from the SmartDelay determined AV optimization: a comparison to other AV delay methods used in Cardiac
Resynchronization Therapy (SMART-AV) trial. Circulation 2010;122:2660–2668
This was a multicentre, randomized trial of atrioventricular (AV) optimization techniques among patients with
advanced HF undergoing CRT defibrillator implantation.

DAVID trial (Dual chamber And Vvi Implanted Defibrillator)
The unexpected increased rates of death and hospital admission for heart failure among patients who were
randomly assigned to the DDDR mode were purportedly due to the adverse effect of RV apical pacing on LV
remodeling.

Frias PA. Evaluation of myocardial performance with conventional single-site ventricular pacing and
biventricular pacing in a canine model of atrioventricular block. J Cardiovasc Electrophysiol 2003;14:
996-1000.
Preclinical data suggested that biventricular pacing might preserve myocardial performance better than right
ventricular apical pacing in patients with atrioventricular block and normal systolic function.

Kindermann M. Biventricular versus conventional right ventricular stimulation for patients with
standard pacing indication and left ventricular dysfunction: the Homburg Biventricular Pacing
Evaluation (HOBIPACE). J Am Coll Cardiol 2006;47:1927-37.
patients with preexisting left ventricular dysfunction and an indication for standard pacing have improved left
ventricular systolic function, exercise capacity, and quality of life after biventricular pacing as compared with
right ventricular apical pacing

In normal subjects RV depolarization precedes LV by a few ms.
2008 ACC AHA guidelines on device based therapy

2013 ESC guidelines on device based therapy

2012 ACC AHA focused update on device based therapy
Regardless of the duration of the native QRS complex, patients with LV dysfunction who have a
conventional indication for pacing and in whom ventricular pacing is expected to predominate may
benefit from biventricular pacing.
LVOT VI for VVD
This technique has been validated in patients with advanced heart failure against the Fick ocygen
reference standard.
Gola A, Pozzoli M, Capomolla S, Traversi E, Sanarico M, Cobelli F, Tavazzi L. Comparison of Doppler
echocardiography with thermodilution for assessing cardiac output in advanced congestive heart failure. Am J Cardiol 1996;78: 708–712.
Some authors have substituted maximal aortic valve VTI using continuous wave Doppler.35 – 38 This
approach is inadvisable as both cardiac output and aortic valve morphology contribute to the signal.
Multiple large randomized trials including InSync IIi and RHYTHM II ICD failed to demonstrate benefit of
VV  optimization using LVOT VTI on the long run.

AVD
The goal of optimizing AVD is twofold. First, to maximize Diastolic Filling Time (E and A separation)
and second to allow complete end diastolic filling (marked by the end of the A wave) before the onset
of LV contraction.

ITERATIVE METHOD
MV PW Doppler. Diastolic Filling Time is measured from the beginning of the E wave to the end of the
A wave.
A long AV delay is programmed and reduced in 20 ms steps until the A-wave truncates. The
interval is then increased in 10 ms increments. The shortest AV delay without A-wave truncation is
selected to maximize DFT.
Over 23 months NYHA and LVEF improved significantly but there were no
control groups. This method was compared against no optimization in a non-randomized
observational cohort study of 100 patients. No significant improvement occurred in any clinical
endpoint, including NYHA class, QOL score, change in 6MWT, death, or cardiac transplantation.
Although Doppler-derived cardiac output increased at 6-month follow-up, LV dimensions and EF were
unchanged.


RITTER'S METHOD
Two extreme AV delays are programmed. A short interval (AV short) with clear A-wave truncation and
a long interval (AV long) without A-wave attenuation (e.g. 30 ms and 200 ms). For each, the time
between QRS onset and completion of the A-wave is measured. The optimal AV delay is calculated
using the formula:
AVopt = AVshort + [(AVlong + QAlong) - (AVshort + QAshort)]
Essentially, this calculates the longest DFT without interruption of the A-wave. Only one small study (n
= 10) validated Ritter’s method in patients with LVSD requiring DDD pacing.
Regardless of the duration of the native QRS complex, patients with LV dysfunction who have a conventional
indication for pacing and in whom ventricular pacing is expected to predominate may benefit from BIV pacing.
A prospective randomized trial published in 2006 concerning patients with LV enlargement, LVEF less than or
equal to 40%, and conventional indications for pacing showed that biventricular pacing was associated with
improved functional class, exercise capacity, LVEF, and serum brain natriuretic peptide levels compared with
RV pacing (298). It has also been demonstrated that LV dysfunction in the setting of chronic RV pacing, and
possibly as a result of RV pacing, can be improved with an upgrade to biventricular pacing (299).

Among patients undergoing
AV junction ablation for chronic AF, the PAVE (Left Ventricular-Based Cardiac
Stimulation Post AV Nodal Ablation Evaluation) trial prospectively randomized patients between RVA pacing
and biventricular pacing (300). The patients with RVA pacing had deterioration in LVEF that was avoided by
the patients with biventricular pacing. The group with biventricular pacing also had improved exercise
capacity compared with the group with right apical pacing. The advantages of biventricular pacing were seen
predominantly among patients with reduced LVEF or heart failure at baseline. Other studies have shown
that among AF patients who experience heart failure after AV junction ablation and RV pacing, an upgrade
to biventricular pacing results in improved symptomatology and improved LV function (301,302).
CRT

Several changes in recommendations for CRT, compared with the 2008 document. The most significant
changes are
1) limitation of the Class I indication to patients with QRS duration >150 ms; The prevalence of mechanical
dyssynchrony has been documented in >40% of patients with dilated cardiomyopathy and QRS duration >120 ms, and is as high as 70% among
patients with QRS duration >150 ms and intraventricular mechanical delay, as identified by several echocardiographic techniques. In a
metaanalysis of 5 trials involving 6501 patients, CRT significantly decreased the primary endpoint of death or hospitalization for HF in patients
with QRS duration !150 ms (HR: 0.58; 95% CI: 0.50 to 0.68; p<0.00001) but not in patients with QRS duration <150 ms (HR: 0.95; 95% CI: 0.83 to
1.10; p=0.51) (569). In addition, subgroup analyses from several studies have suggested that a QRS duration <150 ms is a risk factor for failure to
respond to CRT therapy (570,571). The observed differential benefit of CRT was seen across patients in NYHA classes I through IV. It has not
been possible to reliably identify those with shorter QRS durations who may benefit. Patients with shorter QRS durations who otherwise qualify for
CRT are afforded Class II recommendations in these guidelines.
2) limitation of the Class I indication to patients with left bundle-branch block (LBBB) pattern;
Nevertheless, other studies have shown that CRT is more likely to be effective in patients with advanced HF and non-LBBB morphologies if they
have a markedly prolonged QRS duration  (547,557) (see RAFT [Resynchronization-Defibrillation for Ambulatory Heart Failure Trial].
Furthermore, patients with QRS prolongation due to frequent right ventricular apical pacing may benefit from CRT when other criteria for CRT
are met
3) expansion of Class I indication to New York Heart Association (NYHA) class II (and with LBBB with QRS
duration >150 ms); and
4) the addition of a Class IIb recommendation for patients who have LVEF < 30%, ischemic etiology of heart
failure (HF), sinus
rhythm, LBBB with a QRS duration !150 ms, and NYHA class I symptoms.

Recommendations 3 and 4 are based on 4 studies in which CRT was evaluated in patients with minimal or
mild symptoms of HF in the setting of low LVEF. These include MADIT-CRT, RAFT, REVERSE
(Resynchronization Reverses Remodeling in Systolic Left Ventricular
Dysfunction), and MIRACLE ICD II (Multicenter InSync ICD Randomized Clinical Evaluation II)

MADIT CRT Randomized patients with NYHA class I or II ICM and NYHA class II NICM, LVEF <30%, and
QRS duration >130 ms
on GDMT to CRT-D or ICD alone. Of note, only 15% of the total cohort of patients
were NYHA class I. The primary endpoint, a c
omposite of death or HF event, was reduced by 34% by
CRT-D (HR: 0.66), with comparable benefit for both ischemic and  nonischemic etiology of HF.
HF events
were reduced by 41%
, without significant reduction in mortality rate. CRT-D therapy was
demonstrated to be of more benefit in women than in men (HR: 0.37 and 0.76, respectively) and in patients
with QRS duration >150 ms than in patients with QRS duration <150 ms (HR: 0.48 and 1.06, respectively)
(546). Patients with LBBB had a significant reduction in ventricular tachycardia, ventricular fibrillation, and
death compared to non-LBBB patients, who derived no benefit (HR: 0.47 and 1.24, respectively) (540).

RAFT CRT-D in patients with NYHA class II or class III ICM or NICM, LVEF <30%, and QRS duration
>120 ms
, as compared to those treated with an ICD alone. The primary outcome of death or
hospitalization for HF occurred in 33% of patients receiving CRT-D and in 40% of patients
receiving ICD only
. RAFT not only showed a significant reduction in hospitalization for HF (HR: 0.68; 95%
CI: 0.56 to 0.83; p<0.001) but also was the first study to show a statistically significant reduction in death
(HR: 0.75; 95% CI: 0.62 to 0.91; p<0.003) in mildly symptomatic patients with NYHA class II symptoms.

REVERSE consisted of 610 patients. This study assessed CRT-D therapy in patients with NYHA class I or
II HF symptoms on maximum medical therapy, LVEF <40%, and QRS duration >120 ms followed for
12 months and showed  that 16% of patients receiving CRT and 21% without CRT worsened
(p<0.
10). The time to first HF hospitalization was delayed in patients receiving CRT therapy (HR: 0.47). The
primary echocardiographic endpoint of ventricular remodeling assessed by LV end-systolic volume index
was significantly improved (reduction in end-systolic volume index) in patients treated with CRT therapy (p<0.
0001). REVERSE did not report a mortality rate benefit of CRT-D therapy (548). The lack of reported
mortality rate benefit may be related to the higher ejection fraction enrollment criterion (LVEF "40%) and the
relatively short-term follow-up (12 months) (548).

MIRACLE ICD II included patients with NYHA class II HF on GDMT with LVEF <35% and QRS duration >130
ms who were undergoing implantation of an otherwise indicated ICD (585). In these patients, CRT did not
alter exercise capacity but did result in significant improvement in cardiac structure and function and
composite clinical response over 6 months.

CRT can improve ventricular systolic function, reduce metabolic costs, ameliorate functional mitral
regurgitation, and, in some patients, induce favorable remodeling with reduction of cardiac chamber
dimensions. Functional improvement has been demonstrated for exercise
capacity, with peak oxygen consumption in the range of 1 to 2 mL/kg/min and a 50- to 70-meter increase in
6-minute walking distance, as well as a 10-point or greater reduction of HF symptoms on the 105-point
Minnesota Living with Heart Failure scale.

Trials of CRT confirmed an approximately 30% decrease in hospitalizations and a mortality rate benefit of
24% to 36%.

COMPANION (Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure) trial (NYHA class
III/IV HF, QRS duration "120 ms, and LVEF <35% on GDMT), GDMT was compared to CRT pacing therapy
without backup defibrillation (CRT Pacemaker) and to CRT therapy with defibrillation backup (CRT-D) (543).
Both CRT-Pacemaker and CRT-D reduced the risk of the primary composite endpoint by approximately 20%
as compared with GDMT alone. CRT-D reduced the mortality rate by 36% compared with medical therapy,
but there was insufficient evidence to conclude that CRT Pacemaker was inferior to CRT-D.

CARE-HF (Cardiac Resynchronization in Heart Failure) trial (544) limited subjects to a QRS duration >150
ms (89% of patients) or QRS
duration 120 to 150 ms with echocardiographic evidence of dyssynchrony (11% of patients). It was the first
study to show a significant (36%) reduction in death rate for resynchronization therapy unaccompanied by
backup defibrillation compared with GDMT.

A subanalysis of MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial with Cardiac
Resynchronization Therapy) (546) showed that an
apical LV lead position, as compared with a basal or
midventricular position, resulted in a significant increased risk for HF or
death (578).

The trials showing benefit in NYHA class III and IV patients typically included those with
LVEF <35% (548,585). For patients with NYHA class II, trials showing mortality rate benefit
included those with LVEF <30%. A mortality rate benefit with CRT has not been shown for
patients who are NYHA class I (547).

CRT implantation should be performed only when the LVEF meets guideline criteria for
patients with nonischemic cardiomyopathy who have received >3 months of GDMT, or for
patients with ischemic cardiomyopathy >40 days after myocardial infarction receiving
GDMT when there was no intervening revascularization, or >3 months if revascularization
was performed.

INDICATION FOR CRT-P

CLASS I
1. CRT is indicated for patients who have LVEF less than or equal to 35%, sinus rhythm, LBBB
with a QRS duration greater than or equal to 150 ms, and NYHA class II, (546,547) III, or
ambulatory IV
(542–545); symptoms on GDMT. (Level of
Evidence: A for NYHA class III/IV; Level of Evidence: B for NYHA class II)

CLASS IIa
1. CRT can be useful for patients who have LVEF less than or equal to 35%, sinus rhythm, LBBB
with a QRS duration 120 to
149 ms, and NYHA class II, III, or ambulatory IV symptoms GDMT. (Level of Evidence: B)

2. CRT can be useful for patients who have LVEF less than or equal to
35%, sinus rhythm, a non-
LBBB
pattern with a QRS duration greater than or equal to 150 ms, and NYHA class III/
ambulatory class IV
symptoms on GDMT. (Level of Evidence: A)

3. CRT can be useful in patients with
AF and LVEF less than or equal to 35% on GDMT if
a) the patient requires ventricular pacing or otherwise meets CRT criteria and
b) AV nodal ablation or pharmacologic rate control will allow near 100% ventricular pacing with
CRT (Level of Evidence: B)

4. CRT can be useful for patients on GDMT who have LVEF less than or equal to
35% and are
undergoing new or replacement
device placement with anticipate
d requirement for significant (>40%) ventricular pacing\ (Level
of Evidence: C)

CLASS IIb
1. CRT may be considered for patients who have LVEF less than or equal to 30%, ischemic etiology of
heart failure, sinus rhythm,
LBBB with a QRS duration of greater than or equal to 150 ms, and NYHA class I symptoms on GDMT
(546,547). (Level of Evidence: C)

2. CRT may be considered for patients who have LVEF less than or equal to
35%, sinus rhythm, a non-
LBBB
pattern with QRS duration 120 to 149 ms, and NYHA class III/ambulatory class IV on GDMT
(547,557). (Level of Evidence: B)

3. CRT may be considered for patients who have LVEF less than or equal to
35%, sinus rhythm, a non-
LBBB
pattern with a QRS
duration greater than or equal to
150 ms, and NYHA class II symptoms on GDMT (546,547). (Level of
Evidence: B)

CLASS III: NO BENEFIT
1. CRT is not recommended for patients with NYHA class I or II symptoms and non-LBBB pattern with QRS
duration less than
150 ms (546,547,557). (Level of Evidence: B)

2. CRT is not indicated for patients whose comorbidities and/or frailty limit survival with good functional
capacity to less than
1 year (545). (Level of Evidence: C)
C - vagal. trigger in history nausea. slowing of P-P.
Image is link to article by Ellenbogen in Circulation 2010
In this article, there has been some
speculations about better CRT response in
RBBB with LAD, otherwise known as LBBB
limb leads and RBBB precordials or
LBBB
Masquerading as RBBB,
but this
retrospective analysis of 15k patients in the
Iowa registry shows bad response adn
increased mortality in RBBB patients
despite a median QRS of 15 ms. The
article by Bilchik probably contains data
about the axis. It also identified other
adverse clinical predictors to take into
consideration whenever considering CRT
in a RBBB patient and also associated with
higher mortality.
MADIT-RIT

Inclusion Criteria
Primary prevention patients with no Hx of VT/VF
Sinus rhythm at enrollment; Hx PAF ok
Pt. on stable, optimal pharmacologic therapy
Age >21 yrs; informed consent
Exclusion Criteria
Pt. with pacemaker, ICD or CRT-D device
CABG or PTCA in past 3 months
MI (enzyme +) or AF in past 3 months
2nd or 3rd degree heart block
NYHA IV
Chronic AF
Renal disease: BUN>50mg/dlor Creatinine>2.5mg/dL

Primary end-point
First episode of inappropriate therapy (defined as shock or ATP)
Secondary end-point
All-cause mortality
Syncope

Improved ICD programming to high-rate (>200 bpm) or 60sec duration-delay is associated
with:

~75% reduction in 1st inappropriate therapy;
~50% reduction in all-cause mortality


Dr. Moss and his co-authors speculated that the decrease in mortality in this trial could
have been related to the reduction in inappropriate shock and ATP therapies