Can a pacemaker cause shortness of breath

Pacing and Pacemaker Syndrome

The pacemaker syndrome consists of a constellation of signs and symptoms that result from the loss of AV synchrony during ventricular pacing2,121 (Table 13-5). The definition and diagnostic criteria of pacemaker syndrome vary, but symptoms include fatigue, dyspnea on exertion, paroxysmal nocturnal dyspnea, orthopnea, orthostatic hypotension, and syncope. In the MOST study, pacemaker syndrome was prospectively defined as (1) new or worsened dyspnea, orthopnea, elevated jugular venous pressure, rales, and edema, with ventriculoatrial conduction during ventricular pacing, or (2) symptoms of dizziness, weakness, presyncope or syncope, and reduced systolic blood pressure (>20 mm Hg) during VVIR pacing compared with atrial pacing or sinus rhythm.52,121 The incidence of pacemaker syndrome was 13.8% at 6 months, 16.0% at 1 year, 17.7% at 2 years, 19.0% at 3 years, and 19.7% at 4 years. Univariate predictors of pacemaker syndrome were a higher percentage of ventricular paced beats, a higher programmed lower pacemaker rate, and a slower underlying sinus heart rate. However, only a higher percentage of paced beats was an independent predictor of developing pacemaker syndrome. Quality of life (using various metrics) decreased with the diagnosis of pacemaker syndrome and improved after the pacemaker was reprogrammed to a physiologic mode.121 In the PASE study, of the 204 patients randomized to VVIR, 26% crossed over to DDDR for intolerance to ventricular pacing.49 The Danish study reported a 2% incidence of pacemaker syndrome;48 in CTOPP it was 2.7% at 3 years.50 The incidence of pacemaker syndrome was likely underestimated in these latter two trials, because treatment would have required a surgical intervention. Pacemaker syndrome possibly was overestimated in the MOST and PASE studies, because it was simple to cross patients over to the DDDR pacing mode.121

11 What is pacemaker syndrome?

Historically, pacemaker syndrome refers to progressive worsening of symptoms, particularly congestive heart failure, after single-chamber ventricular pacing. This was due to asynchronous ventricular pacing, leading to inappropriately timed atrial contractions, including those occurring during ventricular systole. Dual-chamber pacing and appropriate pacing mode selection prevent the occurance of pacemaker syndrome. Pseudopacemaker syndrome occurs when a patient without a pacemaker has PR prolongation so severe that the P waves are closer to the preceding R waves than to the following ones, leading to atrial contractions during the preceding ventricular systole.

Pacemaker Syndrome

When first described, pacemaker syndrome was attributed to ventricular pacing and recognized primarily as a problem of single-chamber ventricular pacemakers. However, with the greater use of dual-chamber pacing modes, it has become apparent that pacemaker syndrome is not unique to single-chamber pacing and may occur in different pacing modalities.287-290

Pacemaker syndrome is an array of cardiovascular and neurologic signs and symptoms resulting from disruption of appropriate AV synchrony (AV dyssynchrony) caused by suboptimal pacing, inappropriate programming of pacing parameters, or upper-limit behavior of AV synchronous pacing systems. The pathogenesis of pacemaker syndrome is complex, involving atrial and vascular reflexes and the neurohumoral system as well as the direct hemodynamic consequences of the loss of atrial systole. Patients most prone to the development of pacemaker syndrome are those with 1 : 1 retrograde ventriculoatrial (VA) conduction (Figs. 9-36 and 9-37) and those with lower stroke volume during ventricular pacing than with sinus rhythm or dual-chamber pacing. This syndrome may occur, however, with any mode of pacing that results in permanent or temporary disruption of atrial and ventricular synchronous contraction.

Patients treated with CRT devices may also theoretically demonstrate a pacemaker syndrome caused by inappropriate LA and LV timing. Indeed, interatrial conduction time can be significantly prolonged in patients with dilated cardiomyopathy. During CRT, the contraction of the late-activated region (most often located in LV lateral wall) is advanced to coincide with the start of the contraction of the early-activated region (most often in interventricular septum and RV free wall) to maximize mechanical synchrony and thus efficiency.55,69 In a heart where the LA mechanical contraction has been delayed(e.g., because of combined interatrial block and atrial pacing), LA contraction might occur against a closed mitral valve, especially during BiV pacing, in which LV contraction has been advanced with respect to atrial activation (Fig. 9-38). This phenomenon has been described for patients with pacemakers, in whom the issue is less likely, because RV pacing normally delays the mechanical contraction of the left ventricle, increasing the time available for the left atrium to contract before the mitral valve is finally closed by LV contraction and subsequent pressure increase.151 In NYHA functional classes III and IV heart failure, occurrence of the LA contraction after closure of the mitral valve may trigger sudden increases in pulmonary pressures, similar to cannon A waves seen in pacemaker syndrome (usually observable in jugular veins). These increases could lead to acute decompensation and pulmonary edema in a patient with heart failure. It is also important to realize that this situation could be triggered by atrial pacing because of the increased AV delay that this mode of pacing creates.

Pacemaker syndrome can be treated with an upgrade of the implanted device or with reprogramming of the parameters to achieve the optimal synchrony of atrial and ventricular contraction. Symptoms associated with pacemaker syndrome are variable in severity and onset (Table 9-4). Although the exact incidence is unknown, moderate to severe symptoms of pacemaker syndrome occur in an estimated 5% to 7% of patients in whom the ventricle is mostly paced (Fig. 9-38). Up to 10% of patients undergoing VVI pacing present with mild symptoms.

The pathophysiology of pacemaker syndrome is rather complex, involving hemodynamic, neurohumoral, and baroreceptor changes. In addition to direct hemodynamic effect of loss of AV synchrony or 1 : 1 retrograde VA conduction, atrial and vascular reflexes initiated by atrial distention or elevated atrial pressures may also play a role. Atrial receptors and cardiopulmonary reflexes have been the subject of several in-depth reviews.291,292 Ellenbogen et al.293,294 extensively investigated the role of baroreflex activity during pacemaker syndrome provoked by VA pacing, providing evidence that inadequate systemic sympathetic response plays a key role in the onset of pacemaker syndrome (Fig. 9-39). Indeed, when patients assume an upright position, blood is pooled in the lower extremities, and the arterial baroreceptors are activated to compensate for the decrease in cardiac output and systolic blood pressure. In some patients, pacemaker syndrome results from the inability to compensate further for the upright posture and augmentation of autonomic tone. In other patients, pacemaker syndrome may result from modification of these vascular responses through the effects of drugs, such as vasodilators and diuretics. In still other patients, pacemaker syndrome may result from activation of inhibitory atrial and cardiopulmonary reflexes that counteract the protective vasoconstrictor reflex (see Fig. 9-39). These responses may be further modified by the production of catecholamines and ANF. Circulating levels of ANF are frequently elevated in patients with complete AV block and bradycardia, being reduced within minutes of programming.295,296

Pacemaker syndrome during AAI or AAIR pacing has been described and emphasizes the role of AV dyssynchrony in the pathogenesis. Patients originally undergoing pacing for sick sinus syndrome may later demonstrate AV conduction abnormalities, or AV nodal conduction may be impaired by drugs with AV node–blocking properties (e.g., digoxin, β-blockers, calcium channel blockers, antiarrhythmics), leading to prolonged and hemodynamically unfavorable atrial R-wave (AR) intervals. AV dyssynchrony may also occur in patients with dual–AV nodal pathway physiology during a shift in conduction from the fast pathway to the slow pathway with prolonged AV conduction time. Unfavorable sequencing of atrial and ventricular contractions may occur during AAIR pacing at high sensor-driven rates.288 This situation most often results when the slope determining the sensor-driven rate is programmed too aggressively and out of proportion to the exercise-induced increase in catecholamine levels. As the paced atrial rate progressively increases, the appropriate corresponding decrement in PR interval does not occur, and the interval may even lengthen, eventually resulting in a paced P wave occurring immediately after the preceding R wave (Fig. 9-40). This event most frequently occurs in the earlier stages of exercise and, in some patients, is corrected as the patient continues to exercise.

The VDD pacing mode is similar to DDD mode but without the capability of atrial pacing. The VDD mode, previously out of favor, has been revived by the development of CRT.222,297

Atrioventricular dyssynchrony and pacemaker syndrome may also occur during dual-chamber pacing as a result of inappropriate programming, prolonged atrial conduction time, or normal upper rate limit behavior.289,290,298 In AV sequential pacing modes, selection of an inappropriate AV interval may result in an adverse AV sequencing and hemodynamics. Differential AV intervals for paced and sensed atrial events and rate-adaptive AV intervals are useful in some patients for maintaining AV synchrony over a wide range of heart rates at rest and during exercise.

The maximum atrial tracking rate is determined by the total atrial refractory period (TARP), which is composed of the AV interval and the postventricular atrial refractory period (PVARP). Long AV intervals or long PVARP intervals are sometimes programmed to avoid pacemaker-mediated tachycardia. When the TARP is too long, the maximal atrial tracking rate is low. Patients may experience symptoms of pacemaker syndrome during exercise when their atrial rate exceeds the maximal atrial tracking rate (MATR), resulting in 2 : 1 AV block and a sudden, marked decrease in cardiac output in patients with complete heart block, or in a lack of ventricular pacing in patients with normal AV conduction (crucial in CRT because therapy would stop). This situation may be improved with reprogramming of shorter AV intervals or PVARP intervals to allow 1 : 1 ventricular tracking at higher atrial rates.

Upgrading Techniques

An upgrading procedure is necessary in patients with the pacemaker syndrome. With the growing acceptance of dual-chamber pacing, all patients who have been implanted with VVI systems and who have intact atrial function are now being considered for a pacemaker system upgrade with the addition of an atrial lead. In addition, some patients with an existing pacemaker system need an upgrade to an automatic ICD or a biventricular system for resynchronization. Such patients also need a pacing and shocking electrode and/or a left ventricular lead. Generally, this change is deferred until the time of pulse generator power depletion, but greater awareness of the pacemaker syndrome or the need for an ICD or resynchronization has resulted in earlier pacemaker system upgrades.

The upgrade procedure requires new venous access for the introduction of one or more new leads. It may also involve the introduction of a new ventricular lead because of problems with the existing lead. Most pacemaker system upgrades require the replacement of the pulse generator, although occasionally, the existing pulse generator used in the ventricle can be used for atrial pacing. Upgrade procedures usually involve a conventional approach using one of the previously described percutaneous techniques or a venous cutdown. If the first ventricular lead was placed through the cephalic vein, the percutaneous approach is almost mandatory for the upgrade. Conversely, in patients treated with an initial percutaneous subclavian approach, the new lead can be introduced either by cutdown of the cephalic vein or through percutaneous venous access. In the case of an initial percutaneous approach, the ventricular electrode can serve as a map. Using fluoroscopy, one can use the existing ventricular lead as a target to guide the percutaneous needle. Care should be taken not to touch or damage the first lead with the needle. The lead should be used as a reference landmark for the expected location of the subclavian vein. Bognolo et al.114,115 have described a technique to reestablish venous access using the original ventricular lead. The patency of the venous structures can be assessed as previously described with the injection of radiographic contrast material.91

If access to the subclavian vein cannot be obtained by following the axioms of the safe introducer technique previously described by Byrd,76 an extrathoracic puncture of the axillary vein can be done. The puncture of the vein can be expedited with a simple technique: a guidewire or catheter is passed to the vicinity of the subclavian vein through a vein in the arm. The guidewire or catheter can be palpated or viewed fluoroscopically, thus serving as a reference for venous access. In the case of a cutdown on a previously unused cephalic vein, the Ong-Barold percutaneous sheath set technique can be used.99

Lead compatibility is important when considering a pacemaker system upgrade. To avoid embarrassment, one must be aware of the new pulse generator's compatibility with the chronic lead system.

Occasionally, ipsilateral venous access is impossible. Either the vessel is thrombosed, or some form of obstruction precludes the placement of a second (atrial) lead from the same side. In this case, contralateral venous access can be achieved, and the lead tunneled back to the original pocket (Fig. 21-52). Early injection of radiographic contrast material may expedite the decision to use this approach. The use of the contralateral subclavian (rather than cephalic) vein is recommended for this approach.116 The distance to the original pocket is less, and the new lead is not as susceptible to dislodgement. The same percutaneous techniques and precautions are used as previously described for the percutaneous approach. The only difference is the size of the skin incision, which is limited to about 1 to 1.5 cm. The incision need only be large enough to allow anchoring of the lead and securing of the suture sleeve. As in an initial implantation, the incision should be carried down to the pectoral fascia. Once the lead has been positioned and secured, it can be tunneled to the original pocket.

The maneuver of passing an electrode or catheter through tissue from one location to another is referred to as tunneling. It always involves the passage of a catheter from one wound through tissue to a second wound remote from the first. An example is the placement of a pacemaker lead through the internal jugular vein. The lead is passed from the jugular incision through the tissue over (or under) the clavicle to the pacemaker pocket in the pectoral area. With the development of implantable defibrillator lead and patch systems that do not require thoracotomy, tunneling has become popular and necessary.

A number of techniques are available for tunneling. They differ in level of trauma to the tissue and lead. As a rule, the least traumatic technique is desirable. A popular technique is to place the proximal end of the lead or leads to be tunneled in a 14-inch Penrose drain (Fig. 21-53, A). A gentle, nonconstricting tie is applied around the drain just distal to the lead connector (see Fig. 21-52, B). The track of the tunnel, from the satellite wound to the pocket, is infiltrated with local anesthesia by means of an 18-gauge spinal needle. The free end of the Penrose drain is then brought to the receiving wound from the satellite wound in the subcutaneous tissue. This can be accomplished with several techniques. The first technique involves the use of a Kelly clamp or uterine packing forceps. The tip of the clamp is pushed bluntly in the subcutaneous tissue from the receiving wound directly to the satellite wound. Care is taken to keep the tunnel as deep as possible, usually on the surface of the muscle. The free end of the Penrose drain is grasped and pulled back from the satellite wound to the receiving wound. The remainder of the Penrose drain containing the electrode connector pin is pulled through the track to the receiving wound. The tie is released, and the Penrose drain is removed.

A second technique delivers the Penrose drain to the receiving wound by use of a “passer,” usually a knitting needle or dilator. In this technique, the free end of the Penrose drain is fixed to the back end of the passer with a tie. The pointed tip of the passer is inserted into the satellite wound and pushed to the receiving wound. The tip of the passer is grasped and pulled into the receiving wound with the Penrose drain attached. The remainder of the Penrose drain with the lead is then pulled into the receiving wound.

A variation of this technique uses the percutaneous technique to establish the tunnel. After the track of the tunnel is infiltrated with an 18-gauge spinal needle, the needle is passed from the wound of origin to the receiving wound. A guidewire is passed through the needle into the receiving wound. A standard peel-away introducer is then passed over the guidewire from the satellite incision to the receiving wound. The sheath can then be used to pass the lead, and the sheath is eventually removed and peeled.

Another variation uses the dilator of the sheath set to tunnel and the guidewire to pull the Penrose drain from wound to wound. After the dilator is used to create the tunnel from one wound to the other, the guidewire is passed through the dilator. The dilator is removed, and the guidewire is attached to the loose end of the Penrose drain. The implanter then brings the Penrose drain to the receiving wound by pulling the guidewire.

A technique that is similar in principle to the use of the Penrose drain, but that may be more traumatic, involves the use of a small chest tube and a Pean clamp. The size of the chest tube is determined by the size and number of leads to be tunneled at one time. The length is determined by the distance from the initial wound to the receiving wound. The tube may be cut to size and the end beveled to a point. The leads at the wound of origin are placed in the back end of the chest tube. The Pean clamp is bluntly passed from the receiving wound to the wound containing the leads. The pointed end of the chest tube is grasped by the Pean clamp and is pulled into and through the receiving wound. Although more traumatic to tissue, this technique is protective of the electrodes.

Another related technique involving the use of a chest tube requires blunt passage of the chest tube, with the trocar in place, through the subcutaneous tissue from the site of origin to the receiving wound with the lead or leads placed in the “back end” of the tube after removal of the trocar. The tube can then be pulled through into the receiving wound.

Lastly, new tunneling tools have been developed for use with implantable defibrillators. These tools may be used for pacemaker lead tunneling as well.

The preceding techniques and principles are used whenever tunneling is required. Tunneling with a clamp and directly grasping the lead should always be avoided because of the risk of damage to the lead.

Recently, venoplasty has been introduced as an alternative approach to venous access in situations of subtotal or total venous obstruction. This alternate approach is intended to avoid tunneling techniques or lead extraction as a means of gaining repeat venous access. The tools and techniques of venoplasty are described in Chapter 22.

Mode Selection Trial in Sinus Node Dysfunction (MOST)

The group of investigators of PASE followed their observation that differences in outcome parameters between VVIR and DDDR were (if present at all) more pronounced in sinus node disease, performing a pacing mode comparison in SND patients.67 A total of 2010 patients were randomized to dual-chamber (1014) or ventricular pacing (996) and followed for 33 months. The incidence of the primary endpoint (all-cause mortality or nonfatal stroke) did not differ significantly (21.5% in DDDR, 23.0% in VVIR). Adjusted analyses revealed that in patients assigned to DDDR pacing, the risk of AF was 23% lower (21% vs. 27%) and HF scores were better. Heart failure hospitalization was reduced by 27%, the composite endpoint death, stroke, or HF hospitalization was reduced by 15% (Table 10-9). Dual-chamber pacing resulted in significantly better QOL for six of the eight SF-36 subscales during the 4 years of follow-up. The authors concluded that in SND patients, dual-chamber pacing does not increase stroke-free survival compared to ventricular single-chamber pacing, but DDDR significantly reduces AF risk and HF symptoms and improves QOL.

Pacemaker Upgrades, Revisions, and Generator Replacements

On occasion, it may be necessary to upgrade an existing pacemaker system. This is most commonly encountered in patients with single-chamber ventricular systems who experience pacemaker syndrome, which may be overt or subclinical; this would warrant a switch to a dual-chamber system. Increasingly, patients with congestive heart failure are requiring an upgrade to a biventricular system. Considerable operator experience is required for this upgrading procedure; initial reports of these procedures were associated with a remarkably high complication rate, but it is hoped that it has been reduced over time. Obtaining previous operative notes is extremely useful to ascertain which vein was previously used. If the original route was subclavian, was it because there was no identifiable cephalic vein, or was it the implanter's preference? If the latter, an accessible cephalic vein may well be available to accommodate the new atrial lead, which would require the cutdown technique as previously described. If no cephalic vein is available, the subclavian vein must be used. In case of any doubt as to the viability of the vein vis-à-vis the risk of thrombosis, dye injection of the ipsilateral brachial or axillary vein is helpful. Otherwise, percutaneous subclavian vein entry through the skin or from within the wound is undertaken, with great care to avoid needling or cutting the insulation of the previously implanted lead. Radiographic visualization of the searching needle trajectory is particularly useful in this situation.

If subclavian vein thrombosis is present or the infraclavicular space is too tight to accommodate a second lead (even the smallest unipolar available), then access may be attempted via the contralateral chest with tunneling of the new lead under the skin to the original pacer site (Figure 32-16). The alternative would be to abandon the original site altogether and place a new dual-chamber system via the contralateral chest. If the new lead is to be implanted and tunneled back, a smaller incision can be used; once again, anchoring is of vital importance. For tunneling, a Kelly clamp can be advanced bluntly in the subcutaneous tissue from the receiving (original) site to the satellite (contralateral) site. The free terminal end of the new atrial lead may be placed through a Penrose drain with a gentle tie applied around the drain just distal to the lead connector. The free end of the Penrose drain is then grasped and pulled through the tunnel, back to the original implantation site; the tie is released and the drain is then removed. Alternative approaches include the use of a guidewire and the peel-away introducer technique (introduced from the original site to the satellite location), with passage of the terminal end of the new lead back through the sheath to the original site; a chest tube may also serve as the tunneling conduit. Great care must be taken to strive for a tunnel that is deep (as close as possible to the overlying muscle) and to avoid traumatizing the lead during the tunneling process.

Less commonly, the contralateral site may be used for the new lead, as well as for the creation of a new pacemaker pocket with placement of the new generator. Under these circumstances, the original lead is then tunneled under the skin, by using the same procedure described above, to the new (satellite) location. Depending on the available remaining length of the original lead, a lead extender may be required to traverse the distance to the new site.

Not infrequently, existing lead(s) may deteriorate because of insulation breach or conductor fracture. Placement of a new lead is then required, either through the original site or via the contralateral chest. The same techniques apply, as discussed above, with an upgrade from a single-chamber system to a dual-chamber system. The implanter may decide to abandon the original site altogether and place a new system via the contralateral chest, leaving the original system intact, removing only the old generator (with capping and anchoring of the old lead[s]) or removing of all of the previous hardware (generator and leads). Provided no evidence of infection or erosion is present, old leads may be retained, that is, without mandating extraction.

Generator replacement has been an increasingly important procedure, whether to meet elective replacement indicators or because of device advisories; this undoubtedly reflects the enhanced longevity of patients with pacemakers. It is a commonly undertaken procedure but its importance is often minimized; in fact, it requires a lot of advance thinking. This is particularly the case for the patient with pacer dependence. It is important to establish whether any escape rhythm is present by slowly lowering the programmed rate. If no spontaneous rhythm emerges, consideration must be given to how to maintain perfusion when the old generator is disconnected from the chronic leads. Temporary transvenous pacing or noninvasive external (Zoll) pacing are alternative solutions to quickly changing from the old generator to the new generator (provided that the implanter has nimble hands!). For unipolar systems, as soon as the generator is lifted out of the pocket, capture will be lost; to facilitate conversion to a new generator, a “money clip” may be externally attached to the generator with its associated alligator clip connected to the skin retractor at the pocket site. The new generator must be compatible, either primarily or through adapters, with the existing leads; knowledge of the previous system is therefore critical—with regard to lead manufacturer, nature of the terminal pin, and polarity. Visual inspection of the leads and determination of thresholds and impedances—at baseline as well as with gentle traction on the leads—are all important maneuvers that must be undertaken to make sure that lead replacement is not required (in addition to generator replacement). Rarely, repair of a conductor fracture may be undertaken using splicing techniques; occasionally, a terminal pin modification may be made with splicing techniques if an otherwise-needed adapter is unavailable. Not uncommonly, an anchoring sleeve may be applied with sterile silicone adhesive to repair an insulation breach in the lead. One note of caution that applies to generator changeovers is as follows: An alarmingly higher incidence of infections is noted compared with primary implants because insufficient attention is paid to meticulous aseptic technique during these more ambulatory procedures.

2. Pacemaker Syndrome

Some patients with or without normal ventricular function may experience symptoms with ventricular pacing. These symptoms include exercise intolerance, dyspnea, cough, chest discomfort, abdominal distention, nausea, fatigue and tiredness, dizziness, syncope or presyncope, and hypotension. This constellation of symptoms is referred to as “pacemaker syndrome” and is a result of loss of AV synchrony. The diagnosis of pacemaker syndrome should always be considered when persistent or new symptoms suggestive of low cardiac output or heart failure occur after satisfactory implantation of a permanent ventricular pacemaker. Symptoms may be directly induced or exacerbated by pacing.

A dual-chamber pacemaker is the treatment of choice in patients with pacemaker syndrome. Maintenance of AV synchrony is important in these patients as VAconduction causes hemodynamic derangements that raise atrial pressures and decrease cardiac output with associated symptoms.

Mode Selection Trial in Sinus Node Dysfunction

As previously described, MOST was a randomized study of 2010 patients with sinus node dysfunction who were programmed to ventricular or dual-chamber pacing.35,38 All patients had rate-adaptive pacing. At the last follow-up visit, 31.4% of patients assigned to the ventricular mode had been reprogrammed to dual-chamber pacing, 48.9% of whom were crossed over because of pacemaker syndrome. The diagnostic criteria for the pacemaker syndrome were clearly defined in advance and required “signs and symptoms of elevated right-sided or left-sided filling pressures or hypotension with ventricular pacing.”35 Also, objective measures of QOL improved after reprogramming to dual-chamber pacing, further supporting the diagnosis of pacemaker syndrome.38

There was also a suggestion, albeit inconsistent, of an improvement in overall health-related QOL in patients receiving dual-chamber pacemakers. Three months after device implantation, both the dual-chamber pacing and ventricular pacing groups had significant improvements in SF-36 scores for physical role and physical function. Over 4 years, dual-chamber pacing resulted in greater improvements than ventricular pacing in six of the eight subscales of the SF-36, but not in the Specific Activity Scale.35