US_cardio_Spotnitz.qxp 23/7/08 04:32 Page 70
The Surgeon’s Role in Resynchronization Therapy
a report by
Henry M Spotnitz, MD
and T Alexander Quinn, PhD
1. Department of Surgery; 2. Department of Biomedical Engineering, Columbia University, New York
Surgeons have contributed studies of the pathophysiology and treatment of early success of the Multicenter InSync Randomized Clinical Evaluation
arrhythmias in experimental animals and patients during thoracotomy. (MIRACLE) trial,
implantation of biventricular pacemakers and
This research has involved epicardial
pacemakers and pacemaker ICDs has expanded explosively. The worldwide market for
implantable cardioverter–defibrillators (ICDs).
Surgeons helped to define the resynchronization devices in 2007 is estimated to be in excess of 300,000
mechanisms and ablation methods for supraventricular arrhythmias (including implants annually, at a market value of more than $7 billion for devices
and for ventricular tachycardia associated alone. However, with an incidence of non-responders of 25–30%
with post-infarction, ventricular aneurysms,
and other conditions.
In in the MIRACLE trial
), roughly 90,000 of 300,000 recipients this year
congenital heart disease, techniques for mapping the conduction system were will not experience relief from symptoms of heart failure or functional
developed by surgeons and used to avoid heart block during surgical repair.
benefit. While patients may benefit from defibrillation capabilities in
Therapies for atrial fibrillation developed in the operating room include these implants, the healthcare community will pay more than $2 billion
atrioventricular node ablation
and the Cox-maze operation.
for ineffective resynchronization therapy. Why does resynchronization
Mapping and ablation technologies developed by surgeons have evolved to therapy fail, and how can surgical investigators help?
standard methods used in the electrophysiology lab.
Resynchronization therapy, developed for treatment of heart failure in dilated
However, the development of resynchronization therapy for heart failure cardiomyopathy,
partially reverses the effects of weakening and fibrosis of
has largely bypassed the surgical arena. The epicardial approach has been cardiac myocytes.
Clinical manifestations of myocyte dysfunction include a
marginalized as catheter technology has advanced and concern about left ventricular (LV) ejection fraction (EF) <35% and QRS interval above 120
the risks of general anesthesia and thoracotomy in patients with milliseconds. Left bundle branch block is common in this syndrome.
advanced heart failure has grown.
However, arguably, the minimization Segmental wall motion abnormalities and mitral regurgitation appear as heart
of surgical contributions to resynchronization therapy has left important failure progresses, reflecting the heterogeneity of electrical conduction
gaps in the understanding of how resynchronization therapy works, velocity and contractile function.
The hypothesis that simultaneous pacing of
where it should be applied, and how it can be optimized. Following the the septum and LV free wall could shorten the QRS complex, increase EF,
restore synchrony, and improve symptoms was confirmed clinically.
Resynchronization therapy has been associated with reduced mortality from
Henry M Spotnitz, MD, is the George H Humphreys, II, Professor
of Surgery at Columbia Univeristy. He has been a member of the
heart failure in some settings.
Resynchronization therapy also uniquely
Thoracic Surgery Attending Staff at New York Presbyterian since reduces myocardial oxygen consumption while improving function,
1975. He was previously a Staff Associate at the National Heart
combination previously characteristic only of mechanical assistance devices.
Institute (NHI). His R01 grants (1978–2006) involved the study
of the effects of cardiac surgery on heart function. Professor
Spotnitz’s research interests include myocardial protection in Most resynchronization therapy is performed with endocardial lead insertion
congenital heart disease, pacemaker implants in children, and
under local anesthesia using a limited choice of ventricular pacing sites.
biventricular pacing for acute heart failure. His research is
supported by grants from the American Heart Association (AHA)
Generally, the septum is paced with a conventional lead from the RV apex.
and the National Institutes of Health (NIH), among others. He The LV free wall is paced with a small cross-section lead from a ventricular
received a BA from Harvard and later gained an MD.
branch of the coronary sinus. Inability to enter the os of the coronary sinus
or to find an appropriate, stable location for coronary sinus pacing causes
T Alexander Quinn, PhD, is a Research Assistant at Columbia
failure of implant procedures in 5–10% of candidates.
University. He is experienced with response surface analysis of locations of coronary sinus branches, the tapering cross-section of those
complex data sets and hybrid computer development for the
branches, and limitations of current technology reduce the number of usable
automated pacing and detection of compliance abnormalities. He
was a Moderated Poster Presentation Award winner at the
pacing sites in any given patient.
The ability to objectively compare small
American Society for Artificial Internal Organs (ASAIO) 50th hemodynamic effects of pacing from different sites is limited by the time
Anniversary Conference and a Finalist (second place) in the PhD
required to reposition the LV lead, optimally requiring multisite electrodes.
Student Paper Competition at the American Society of Mechanical
Engineers (ASME) Summer Bioengineering Conference. Mr Quinn
Despite these difficulties, available data indicate that the location of the LV
received a BSci in physiology and physics from McGill and an MS free wall lead is an important determinant of the efficacy of resynchronization
and PhD in biomedical engineering from Columbia University.
therapy. Lateral and inferior LV lead locations have been utilized empirically.
In dilated cardiomyopathy, it has been suggested that the LV lead should be
70 © TOUCH BRIEFINGS 2008
| Page 2
| Page 3
| Page 4
| Page 5
| Page 6
| Page 7
| Page 8
| Page 9
| Page 10
| Page 11
| Page 12
| Page 13
| Page 14
| Page 15
| Page 16
| Page 17
| Page 18
| Page 19
| Page 20
| Page 21
| Page 22
| Page 23
| Page 24
| Page 25
| Page 26
| Page 27
| Page 28
| Page 29
| Page 30
| Page 31
| Page 32
| Page 33
| Page 34
| Page 35
| Page 36
| Page 37
| Page 38
| Page 39
| Page 40
| Page 41
| Page 42
| Page 43
| Page 44
| Page 45
| Page 46
| Page 47
| Page 48
| Page 49
| Page 50
| Page 51
| Page 52
| Page 53
| Page 54
| Page 55
| Page 56
| Page 57
| Page 58
| Page 59
| Page 60
| Page 61
| Page 62
| Page 63
| Page 64
| Page 65
| Page 66
| Page 67
| Page 68
| Page 69
| Page 70
| Page 71
| Page 72
| Page 73
| Page 74
| Page 75
| Page 76
| Page 77
| Page 78
| Page 79
| Page 80
| Page 81
| Page 82
| Page 83
| Page 84