© 2005 The European Society of Cardiology. Published by Elsevier Ltd. All rights reserved.
Commentary on the abstracts for Cardiostim 2005 Pacing and Haemodynamics: Art of Timing Budapest, Hungary, April 6–8, 2005
Centre Chirurgical Val D'Or, Department of Cardiology 12 rue Pasteur, 92210 Saint-Cloud, France
Tel.: +33 141120710; fax: +33 146020509. E-mail addresses: cardiostim{at}wanadoo.fr
Key Words: Cardiostim 2005, pacing, cardiac resynchronisation therapy
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Introduction |
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 Top Introduction Conventional pacingCardiac resynchronisation... |
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The Cardiostim team and Prof. Aladar Ronaszeki organised an educational meeting in Budapest from April 6 to 8 entitled "Pacing and Haemodynamics: Art of Timing".
This European congress has been an opportunity to discuss the haemodynamic effects of the various modes of pacing available, and more specifically Cardiac Resynchronisation Therapy (CRT) for heart failure patients.
The reader will find below the 101 abstracts selected among the 156 received, printed in three different sections: conventional pacing, CRT, and a small set of abstracts on ablation techniques, which will not receive comment.
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Conventional pacing |
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TopIntroductionConventional pacingCardiac resynchronisation... |
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Many investigations have demonstrated the deleterious effects of right ventricular (RV) apical pacing. Padeletti et al. (for the WHERE study) elegantly show the benefit of preserving spontaneous AV conduction in comparison with RV apical pacing, in DDD paced patients, via PEA measurements. PEA, which has been demonstrated to be closely correlated with LV dP/dt, significantly increases when patients are not RV paced, and decreases when they are RV paced. PEA variations parallel clinical outcomes and echo parameter values.
When pacing is necessary, there is still controversy about the optimal RV pacing site.
Direct His bundle pacing is feasible and safe (Catanzariti et al.), but requires normal function of the bundle branches and Purkinje system. Implantation is also difficult to perform. Long term reliability of His pacing is unknown.
For Kutarski et al., RV outflow tract (RVOT) pacing is preferable to RV apical pacing. But for van Gelder, RV apical pacing is preferred for CRT patients. In our experience, RVOT and RV apical pacing provide similar haemodynamic results on average, but may induce significant individual differences.
To help to understand individual requirements, one of the main targets for manufacturers is to propose haemodynamic sensors that could evaluate and guide the benefits of various pacing sites, such as PEA or transvalvular impedance (Chirife et al.).
In the heart failure population, the bifocal RV (BRV) configuration has been introduced as an alternative technique to CRT, especially in case of LV lead implant failure. Authors (Chudzik, Kutarski, Res, Matsushita) report on the beneficial effects of this method. However, there is no report, so far, comparing CRT including a LV lead, with bifocal RV pacing. According to personal data, a bifocal RV pacing system cannot be recommended instead of a biventricular device. Once again, some individuals benefit from a bifocal device, whereas a majority of patients benefit from a biventricular device. A practical question remains: in case of LV lead implant failure, should we go immediately to surgery for an epicardial LV lead implant, or should we implant a bifocal RV system, analyse the patient's clinical outcome, and go to surgery in case of patient's non-response? In the latter situation, the system would become an atrio-triventricular system, which does not exist for the moment!
Vogt et al. and Van Gelder et al. deal with LV pacing alone and tailoring of a CRT device. Beyond the reported results, authors insist upon careful tailoring of CRT devices. CRT is used in severe heart failure patients in whom a slight improvement in heart function may induce tremendous clinical benefits. Each additional benefit will improve further the clinical outcome of the patient. ‘All CRT devices must be carefully tailored to the patient's status!’ There is no doubt that, in the future, haemodynamic sensors will pilot devices automatically to determine the optimal configuration in the various situations that patients can meet.
In this respect, AV delay optimisation remains critical in all atrio-ventricular pacing configurations. Authors agree that preserving spontaneous AV conduction and mechanical ventricular contraction sequence is preferable to any kind of ventricular pacing in normal heart patients. However, Bohm et al. remind us that pacemaker syndrome can be induced by AAIR pacing during heavy exercise, when the spike A–R interval prolongs so much that atrial contraction occurs during ventricular systole of the previous cycle, at a moment when AV valves are still closed. Exercise performance falls, and atrial stretch is promoted, which may induce arrhythmias. There is still work for engineers to determine which pacing mode should be applied in this condition (12/49 patients in Bohm's abstract). Again, haemodynamic sensors might bring an automatic answer to this problem: optimal rate-responsiveness according to exercise workload, triggering of DDD mode with optimal AVD.
Babu et al. describe a method using pulse oximetry to determine the individual optimal AVD (OAVD), and show that its value remains stable over time. This confirms our own observation. When heart condition remains stable, OAVD does not change over time. As a matter of fact, its value changes in CRT patients when heart dimensions decrease: most of the time, OAVD has to be extended. Another situation where OAVD is critical is hypertrophic cardiomyopathy (HCM). Knyshov et al. propose a method for its determination in this condition. Returning to CRT, Chirife et al. remind us that CRT does not affect only ventricular contraction time intervals, but that diastolic function improvement and reduction in mitral valve regurgitation during systole are also of major importance in the clinical outcome, something that many authors exclude from their papers or lecture discussions.
The value of AVD does influence mitral regurgitation: it is probably more important to reduce MR than optimising A wave timing in relation to LV contraction to achieve the maximal response from CRT.
OAVD must be applied in all pacing situations, such as atrial sensing and pacing. Ismer et al. propose a method to determine OAVD easily and the difference in AVD to be programmed. Again this latter value is individual and depends on the location of the right atrial lead.
Braunschweig et al. report the usefulness of an implanted haemodynamic monitor to determine automatically individual OAVD, based on the estimation of pulmonary artery diastolic pressure.
Vitali et al. compare OAVD obtained from PEA measurement and OAVD by echo, and show an excellent correlation. They also demonstrate that OAVD shortens on exercise, and that this method could be implemented in an automatic function to tailor accurately AVD to the individual patient at rest and during daily life activities, thus, reducing time and cost of follow-up. Atrial contribution should be respected in patients with poor left ventricular condition.
Pacing in children is a particular topic, and position of leads and choice of the pacing mode impact haemodynamics in the long term. Bockeria et al. report results on the impact of the RV lead position and prefer the interventricular septal site. In two other abstracts, they report favourable outcomes when physiological modes are used in comparison with single ventricular modes, and that supraventricular arrhythmias are more frequent with these latter modes. However, Shalganov et al. do not reveal any decline in LV function with chronic RV pacing in their population of paediatric patients, with or without heart disease. The last abstract of this series, by Környei et al., demonstrates that CRT pacing can be applied in a very young infant with improvement in echocardiographic and clinical status. These abstracts suggest that our strategies should not change in comparison with paced adults. The main problem remains the occupation of the venous network by the pacing leads, which, without any doubt, will have to be changed during the life of these young patients.
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Cardiac resynchronisation therapy |
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TopIntroductionConventional pacingCardiac resynchronisation... |
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CRT is a novel therapy applied to patients with heart failure, dilated heart, and mechanical ventricular asynchrony. It has been shown as being efficient in ischaemic and non-ischaemic heart disease, in sinus rhythm and atrial fibrillation patients.
Chalil et al. compare cardiac magnetic resonance and echo for the estimation of LV function and show that echo-derived LV ejection fraction calculation is inadequate to obtain a precise measurement. Nevertheless, for Cozma et al., the echo technique is a reliable method to assess LV asynchrony. They compare the Global Myocardial Index (GMI) with LV mechanical delays and show that the correlation between the parameters is excellent with a high positive predictive value and acceptable negative predictive value when the GMI cut-off is >0.87. GMI, which includes isovolumetric contraction and relaxation, filling and ejection times in its calculation, is thus an excellent parameter to diagnose LV asynchrony, as suggested by Cazeau since the beginning of CRT. Karagiannis et al. explore mitral valve movements and more specifically the distance between the coaptation point of mitral leaflets and mitral annulus, and the mitral valve annulus diameter. They show an improvement in both parameters when CRT is turned on, an indirect observation of the resynchronisation of LV segmental contraction.
Ventricular resynchronisation is the goal to achieve in CRT, whereas pacing-induced ventricular asynchrony is mandatory in HCOM patients to reduce intra-LV systolic pressure gradient and mitral regurgitation. Knyshov et al. demonstrate that the benefit of dual chamber pacing in HCM is related to the degree of the LV asynchrony induced by pacing between LV apex and papillary muscle activation, and the hypertrophied interventricular septum activation. This expected effect can only be obtained when ventricular capture is applied at the cost of short AV delays, but respecting the completion of the active phase of ventricular filling.
Müller et al. report a very interesting experimental observation on the modulation of collagen synthesis of cardiomyocytes by the application of micro-current. Modulation of collagen type I, which impacts the stiffness and degree of cardiac dilatation, could be a new means to alter heart function.
CRT offers long term benefits as reported by Baracca et al., in a large unselected population of 174 patients, during a long term follow-up of 25 months. Reverse remodelling of the left ventricle, assessed by echo, is observed in one third of patients in a cohort of 39 subjects from Guyomar et al. They also report a clinical fact: this remodelling can be very quick or delayed, a quite variable and individual response.
Azizi et al. report on the morbidity of CRT in 234 patients. Coronary sinus dissection, lead dislodgement, phrenic nerve stimulation, and ventricular fibrillation are the most common complications. Anterior coronary sinus lead positions do not provide good outcomes. At our institutions, we consider these positions as failures of the implant procedure!
Implemented haemodynamic sensors are new tools to evaluate the clinical outcome. Nagele et al. report on the Optivol® system, which measures thoracic impedance, thus estimating the presence and amount of fluid in lungs. The provided information correlates well with the clinical data. In the same way, Plicchi et al. use PEA to evaluate the CRT response and to guide reprogramming of the implanted system. These examples demonstrate the clinical usefulness of such sensors to evaluate the patient's outcome, and thus, could be useful tools to adjust the therapy according to the various needs of the patient.
Chalil et al. evaluate the percentage of scar volume by gadolinium DPTA-enhanced magnetic resonance and show that myocardial viability evaluation prior to CRT implant is a good predictor of the response to CRT. This type of technology will develop rapidly and it is probable that the way we select patients for CRT will be totally different in the future to ensure the clinical benefit that we expect from the technique.
CRT can provide good results in various cardiac conditions.
De Cock et al. show that angina remains stable when CRT is used in patients in whom revascularisation is not indicated. Furthermore, they demonstrate an improvement in exercise capacity whereas angina attacks/week remain the same. It is probable that the presence of the implanted device allows improvement in the medical therapy to achieve these results, something that we experienced at our centres.
Sredniawa et al. confirm the reduction in sleep apnoea parameters in their study population.
We should not give up when patients present with unstable heart failure, as Chalil et al. demonstrate a favourable clinical outcome with CRT for these patients, a result confirmed by Stockburger's study. This issue is of major importance. We know that Class III (and even Class II) patients are good candidates for CRT, which improves the functional capacity and decreases the number of hospitalisations. Even if we all started CRT with Class IV patients, we know that the prognosis is much worse in this population. Patients in Class IV at the moment of CRT implant respond less to the therapy, and die more. However, we also have good individual results in this population. One of the major issues for the future of this therapy is to determine the moment when it must be applied to prevent deterioration of the patients, when they are still at an early stage of heart failure, and the moment when it is too late to expect any benefit because the status of the patients is too poor. In our experience, prognosis is bad when the patient presents with right heart failure in addition to left heart failure.
Patients who are already implanted with a conventional pacemaker benefit substantially from an upgrade to biventricular pacing, as shown by Hoijer et al., a result that is similar to the RD-CHF trial. The model of ventricular asynchrony induced by RV pacing is probably different from the one that results from cardiac disease. It can be totally suppressed by the addition of a LV lead. LV asynchrony induced by RV pacing may be responsible per se for the heart failure status of some patients, as we experienced the return to a normal heart condition in some of our paced patients after upgrading their pacing system, patients in whom no heart disease, except heart dilatation, was found. The RV pacing-induced heart failure should be described as a separate entity in these patients.
De Fabrizio et al. show the combined benefit of AV node ablation and CRT in patients with chronic AF with fast ventricular response. In our experience, this strategy is systematically used in this population with consistent results.
Kutarski et al. show how to tailor the VV interval value to the individual, using the transthoracic bioimpedance method, which offers a simple and global assessment of heart function.
Should we use more sophisticated but more precise methods to perform this work? This issue remains complex, and is not easily applicable in clinical practice. Van Gelder et al. use the LV dP/dt measurements to programme the individual parameters. The optimal VV interval may be quite different from one patient to another, and may even vary at different pacing rates, and in various directions individually. Again, these results demonstrate that this task remains quite difficult, especially in some configurations, when pacing from the anode of the right ventricular lead can be observed (as suggested by van Gelder). This observation will probably be reported on the left ventricular lead as well in the near future, as LV bipolar leads are now available! What is the best method to determine the optimal pacing configuration during CRT? LV dP/dt, a parameter influenced by ventricular filling and contractility, is probably the most interesting and is the basic parameter used in all invasive work in the field. Could it be the echo evaluation, as suggested by Stahlberg et al. In our experience, echo is difficult to use in practice, because the procedure may be quite long for the optimal VV programming, so that the stability of haemodynamics cannot be ascertained throughout the echo investigation. Again, implemented haemodynamic sensors could be the answer, as demonstrated by Marcelli et al., who use the PEA measurements made by the pacing system itself, values well correlated with LV dP/dt. The advantage of this would be the automatic adaptation of the system to the variations in the haemodynamic status of the patient.
To obtain correct results, the quality of implantation of the CRT system is critical, a task that is frequently a challenge. I am convinced that visualisation of the coronary sinus and its tributaries is mandatory before the implant procedure to determine the type of leads and strategies to be used to achieve the goal. In this respect, Giraldi et al. performed computed tomography to estimate better the position of the coronary sinus within the right atrium, its diameter, and diameter and angulation of the CS tributaries. Authors show that CRT implantation can be achieved quicker, and consequently with less radiation exposure.
D'Ivernois et al. report on the use of VDD leads for CRT, in order to reduce the number of leads and implant time. The problem remains to ensure 100% atrial sensing to allow permanent atrio-ventricular synchrony.
Concerning the LV pacing site, Kowalski et al. confirm that lateral and postero-lateral positions offer the same results. In our group, we have established the following rule: a LV lead implant failure is a lead that cannot be implanted for any reason (no LV pacing because of very high thresholds, phrenic nerve stimulation, instability of the lead), but also a lead that cannot be implanted at a lateral site (antero-lateral, lateral, or postero-lateral). With this definition of LV lead implant failure, our failure rate is more than 10%.
Gadler et al. demonstrate that the Autocapture® feature can be applied on LV pacing, regardless of the stimulation "ignition", or the programmed VV interval. This method is thus important to ensure 100% biventricular pacing.
All manufacturers produce specific leads for a transvenous approach to the coronary sinus, and as mentioned above, we still experience a too high failure rate although this technique was introduced in 1994. Consequently, many colleagues propose a surgical epicardial approach, which remains dangerous in these fragile patients. To solve this problem, other proposals were made in the recent past such as the atrial transseptal approach. Mickelsen et al. offer another technique: the transvenous catheter-based approach to epicardial lead implantation. This technique was tested in pigs with success at the cost of limited pericardial effusion. Will it become a procedure transposed to humans? This concept is very interesting and may undergo further development.
One of the main issues remains the determination of the predictive factors of the outcome of heart failure patients. For Hatzinikolaou-Kotsakou et al., the preimplant CRP plasma level is an independent predictor of ICD shock in patients with cardiomyopathies, as increased levels of NT-proBNP are in the ICD population observed by Mavrakis et al.
For Giraldi et al. and Sredniawa et al., CRT markedly improves heart rate variability, which thus could be a predictive marker of a favourable outcome in CRT patients, whereas Chalil et al. report increased QT dispersion in patients dying from sudden cardiac death during follow-up after CRT implantation. Risk factors for sudden cardiac death in candidates for CRT implant should be investigated more. After MADIT II, SCD-Heft and COMPANION trials, colleagues of various Nations no longer discuss the type of device to be implanted for CRT: pacemakers or ICDs. As an example, nowadays, American and German colleagues only implant CRT-D devices. In many other countries, where resources are quite limited, the decision making is much more difficult as colleagues have to treat the maximal number of patients with a given minimal budget! Then, the choice between CRT-P and CRT-D becomes critical, and determination of the population most at risk for sudden cardiac death is a prerequisite before implanting a CRT-D device. In France, a new law has been published recently that allows selected centres to implant ICDs and CRTs, and thus the rate of implant of these devices should increase in this country. However, the official National recommendations have not been revisited in the light of the most recent trials, and those included in the law cannot use primary prevention indications. As a matter of fact, for the moment, the indication for CRT-D remains based on the combined indication of CRT and ICD. Determination of risk factors is thus an important argument in selection of the implantation of CRT-D, when economic restrictions are facing the local medical community.
In the last part of this second section on CRT, the reader will find below the abstracts that were selected for poster presentations.
Goscinska-Bis et al. demonstrate the benefit of an atrio-triple ventricular pacing configuration after failure of the atrio-RV bifocal pacing system, with huge reduction in LV asynchrony and in mitral regurgitation. We have started to experiment with atrio-triple ventricular pacing at our institutions, in patients who were first implanted with a biventricular system, with good initial results. Then, those patients deteriorated again in long term follow-up with reoccurrence of LV asynchrony. After addition of a RV lead, distant from the first RV lead previously implanted, all patients recovered with stable cardiac condition in the long term.
The same team reports three patients implanted with a CRT device during a CABG procedure, with excellent clinical improvement. All patients were desynchronised before heart surgery. This strategy is probably underused in patients with dilated hearts, LV asynchrony and candidates for any cardiac surgery. In our experience, all patients who are referred to us for CRT implant with LV asynchrony undergo a coronary artery angiogram with venous return for assessment of heart vascularisation, and visualisation of coronary sinus tributaries prior to implant. In some cases, serious coronary artery stenoses are diagnosed which are amenable to angioplasty and stenting, or CABG. In all patients with such an initial profile, who did not improve their LV function and were still symptomatic after heart intervention, we had to proceed to CRT implantation some weeks after revascularisation, because LV asynchrony was still present. Consequently, simultaneous CRT implantation and heart surgery does not appear to be a foolish strategy in patients with huge LV dilatation and cardiac asynchrony.
Various abstracts describe the beneficial effects of CRT: reduction in systolic time intervals analysed by PEA measurements correlated with echo findings (Ritter et al.), restoration of synchronous contraction of basal LV segments with reduction in mitral regurgitation (Dalamanga et al.).
Again, some authors confirm that it becomes possible to analyse the evolution of the heart condition via implemented haemodynamic sensors, again with PEA for Plicchi et al., and with analysis of ventilatory and exercise parameters for Jauvert et al.
All those submitted abstracts provide a useful update of the state of the art in CRT. The common trend is to evaluate the patients through a mechanistic approach rather than from the calculation of the QRS duration on ECG. Most authors use sophisticated echo software or new imaging technologies to assess precisely the baseline mechanical profile of the heart, understand the mechanical alterations imposed by CRT, and perform the long term follow-up. These investigations require high standard equipment, long procedures, and lots of energy from the medical staff. In the future, devices will do the job for us, in a quicker and more reliable way, because manufacturers implement haemodynamic sensors in devices, which will facilitate and accelerate evaluation processes. There is no doubt that the next decade will be the witness of the expected advantages of these new technological advances.
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