- Email: [email protected]
A treatment option for some failing hearts
The American Journal of Medicine (2005) 118, 368-370
ECG IMAGE OF THE MONTH
A treatment option for some failing hearts Julia H. Indik, MD, PhD, ECG Image of the Month Editor University of Arizona, Sarver Heart Center. In recent years, the prognosis for patients with heart failure has improved substantially with advances in both pharmacologic treatments and the application of implantable devices. One new technology, cardiac resynchronization therapy (CRT), has emerged as an effective method for selected patients. Also known as biventricular pacing, it has been demonstrated in major trials1,2,3 and, when coupled with a defibrillator, to improve survival as well.3 For these reasons, it is important to know which patients are possible candidates for biventricular pacing and to understand its mode of action.
What it does The goal of biventricular pacing is to achieve resynchronization of left ventricular wall motion. For example, wall motion is generally dyssynchronous in the setting of left bundle branch block (LBBB). When electrical conduction can only proceed along the right bundle, the ventricular septum is stimulated from right to left with very slow activation of the remainder of the left ventricle. In particular, the lateral wall may be set in motion 100 msec or more after activation of the septum. As a result, lateral wall movement may occur so late in the cardiac cycle that is contributes little to mechanical systole. Placement of a pacing lead within a coronary sinus branch that lies along the epicardial lateral wall of the left
Requests for reprints should be addressed to Julia H. Indik, MD, PhD, University of Arizona, Sarver Heart Center, 1501 N. Campbell Avenue, Tucson, Arizona 85724. E-mail address: [email protected].
0002-9343/$ -see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.amjmed.2005.01.039
ventricle allows for simultaneous activation of the lateral wall and septum, improving the efficiency of ventricular contraction.
When it’s used CRT should be considered for patients with heart failure who have advanced left ventricular dysfunction with a QRS duration of at least 130msec, who meet the criteria of New York Heart Association functional class III or IV, and who are already receiving optimal medical therapy. In some cases, echocardiography using tissue Doppler imaging is needed to discern whether significant dyssynchrony exists. For example, a biventricular ICD has been placed in a patient with LBBB. A baseline ECG displays a sinus rhythm with a prolonged PR interval of 240msec and a very wide QRS of 220msec (Figure 1). The typical hallmarks of LBBB are evident: the voltage in V1 is negative; the QRS duration is greater than 120msec; and leads I, V5 and V6 show a wide and notched R wave with no Q wave. A normal QRS complex should display a very small Q wave in these three leads. An ECG following the procedure clearly illustrates the favorable effects of biventricular pacing (Figure 2). Note that there is a sinus rhythm of 80 bpm, and the PR interval has been shortened to 130 msec, which improves cardiac filling during diastole. The QRS complex, slightly narrower than baseline at 180msec, represents a fusion of simultaneous pacing from both the right and left ventricles. A look at data from lead V1 indicates that the paced QRS complex is now almost positive, and in fact, the presence of left ventricular pacing almost gives it the appearance of right bundle branch block. Furthermore, the paced QRS complex in lead I is now negative, indicating that voltage is traveling away from the left side of the heart. This is the opposite of what would be
Indik
Treatment Option for Failing Hearts
Figure 1
369
The patient’s initial ECG provides characteristic evidence of left bundle branch block.
seen in standard pacing of only the right ventricle. In that situation, the paced QRS complex resembles the pattern produced by LBBB—it would be negative in lead V1 and
have a large positive R wave in lead I. A chest x-ray clearly depicts the device and the positioning of the pacing wires (Figure 3).
Figure 2 With biventricular pacing, the QRS is now negative in lead I and almost positive in V1. The PR interval has been shortened to 130 msec to improve ventricular filling during diastole.
370
The American Journal of Medicine, Vol 118, No 4, April 2005
Figure 3 The black arrows highlight pacing wires in the right atrium and the right ventricle. A third pacing wire is in the coronary sinus where it enters a sinus branch that reaches the lateral wall of the left ventricle, as shown by the white arrows in the posterior-anterior view. In the lateral view, the third wire runs in a posterior position.
References 1. Cazeau S, LeClercq, Lavergne T, et al. Effects of multisite biventricular pacing in patients with heart failure and intraventricular conduction delay. New Engl J Med. 2001;344:873– 880. 2. Abraham WT, Fisher WG, Smith AL, et al., for the MIRACLE study
group. Cardiac resynchronization in chronic heart failure. N Engl J Med. 2002;346:1845–1853. 3. 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 – 2150.
ECG IMAGE OF THE MONTH
A treatment option for some failing hearts Julia H. Indik, MD, PhD, ECG Image of the Month Editor University of Arizona, Sarver Heart Center. In recent years, the prognosis for patients with heart failure has improved substantially with advances in both pharmacologic treatments and the application of implantable devices. One new technology, cardiac resynchronization therapy (CRT), has emerged as an effective method for selected patients. Also known as biventricular pacing, it has been demonstrated in major trials1,2,3 and, when coupled with a defibrillator, to improve survival as well.3 For these reasons, it is important to know which patients are possible candidates for biventricular pacing and to understand its mode of action.
What it does The goal of biventricular pacing is to achieve resynchronization of left ventricular wall motion. For example, wall motion is generally dyssynchronous in the setting of left bundle branch block (LBBB). When electrical conduction can only proceed along the right bundle, the ventricular septum is stimulated from right to left with very slow activation of the remainder of the left ventricle. In particular, the lateral wall may be set in motion 100 msec or more after activation of the septum. As a result, lateral wall movement may occur so late in the cardiac cycle that is contributes little to mechanical systole. Placement of a pacing lead within a coronary sinus branch that lies along the epicardial lateral wall of the left
Requests for reprints should be addressed to Julia H. Indik, MD, PhD, University of Arizona, Sarver Heart Center, 1501 N. Campbell Avenue, Tucson, Arizona 85724. E-mail address: [email protected].
0002-9343/$ -see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.amjmed.2005.01.039
ventricle allows for simultaneous activation of the lateral wall and septum, improving the efficiency of ventricular contraction.
When it’s used CRT should be considered for patients with heart failure who have advanced left ventricular dysfunction with a QRS duration of at least 130msec, who meet the criteria of New York Heart Association functional class III or IV, and who are already receiving optimal medical therapy. In some cases, echocardiography using tissue Doppler imaging is needed to discern whether significant dyssynchrony exists. For example, a biventricular ICD has been placed in a patient with LBBB. A baseline ECG displays a sinus rhythm with a prolonged PR interval of 240msec and a very wide QRS of 220msec (Figure 1). The typical hallmarks of LBBB are evident: the voltage in V1 is negative; the QRS duration is greater than 120msec; and leads I, V5 and V6 show a wide and notched R wave with no Q wave. A normal QRS complex should display a very small Q wave in these three leads. An ECG following the procedure clearly illustrates the favorable effects of biventricular pacing (Figure 2). Note that there is a sinus rhythm of 80 bpm, and the PR interval has been shortened to 130 msec, which improves cardiac filling during diastole. The QRS complex, slightly narrower than baseline at 180msec, represents a fusion of simultaneous pacing from both the right and left ventricles. A look at data from lead V1 indicates that the paced QRS complex is now almost positive, and in fact, the presence of left ventricular pacing almost gives it the appearance of right bundle branch block. Furthermore, the paced QRS complex in lead I is now negative, indicating that voltage is traveling away from the left side of the heart. This is the opposite of what would be
Indik
Treatment Option for Failing Hearts
Figure 1
369
The patient’s initial ECG provides characteristic evidence of left bundle branch block.
seen in standard pacing of only the right ventricle. In that situation, the paced QRS complex resembles the pattern produced by LBBB—it would be negative in lead V1 and
have a large positive R wave in lead I. A chest x-ray clearly depicts the device and the positioning of the pacing wires (Figure 3).
Figure 2 With biventricular pacing, the QRS is now negative in lead I and almost positive in V1. The PR interval has been shortened to 130 msec to improve ventricular filling during diastole.
370
The American Journal of Medicine, Vol 118, No 4, April 2005
Figure 3 The black arrows highlight pacing wires in the right atrium and the right ventricle. A third pacing wire is in the coronary sinus where it enters a sinus branch that reaches the lateral wall of the left ventricle, as shown by the white arrows in the posterior-anterior view. In the lateral view, the third wire runs in a posterior position.
References 1. Cazeau S, LeClercq, Lavergne T, et al. Effects of multisite biventricular pacing in patients with heart failure and intraventricular conduction delay. New Engl J Med. 2001;344:873– 880. 2. Abraham WT, Fisher WG, Smith AL, et al., for the MIRACLE study
group. Cardiac resynchronization in chronic heart failure. N Engl J Med. 2002;346:1845–1853. 3. 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 – 2150.