As some pregnant patients have pacemakers due to congenital heart defects, preconception counseling to discuss fetal risks for cardiac anomalies may need to be employed. It is well established that fetal risk for cardiac anomaly is 2-5 times greater if the affected patient is the mother (Table 2) [21] . Of note, the cardiac anomalies are not always the same as those of the parent. Additionally, some cardiac lesions may be a part of a larger syndromic diagnosis in the parents, and therefore genetic counseling may need to be expanded beyond cardiac concerns [22] . Importantly, several of these conditions have specific genetic markers that can be tested using either chorionic villus or amniocentesis-derived samples. Preconception counseling also allows for a thorough evaluation of the maternal cardiac status, with the opportunity to optimize her condition, preemptively modify pharmacologic agents appropriate for pregnancy, and deal with other comorbidities that may have an effect on pregnancy [23] .

Usually patients with pacemakers tolerate the pregnancy well. The few reported maternal complications appeared to be isolated to patients with underlying structural heart disease [24] . Thaman et al. [24] reported their experience with 11 pregnant patients with pacemakers. Three of these patients, who had underlying structural heart disease, developed maternal complications. One patient developed cardiac decompensation in the third trimester and was induced at 38 weeks. The other developed recurrent palpitations secondary to a short run of atrial fibrillation. Both these patients had uneventful deliveries and postpartum courses. The third patient developed progressive right ventricular failure and had an intrauterine fetal death at 20 weeks gestation. Although these data suggest the need for more careful surveillance when a structural heart defect is associated with pacemaker usage, given the very limited nature of these reported events, a firm recommendation cannot be established.

With regard to routine care, co-management with the cardiology service is required. Either before the pregnancy or early in the first trimester, an EKG, echocardiogram and baseline pacemaker interrogation should be done. Device interrogation can provide information about pacemaker dependency. Pacemaker dependent patients may have no or very slow escape rhythms and require extra precautions during surgery. Throughout the pregnancy, attention should be paid to any new onset of symptoms such as palpitations, shortness of breath, syncope, seizure-like activity, dizziness, confusion, and exercise intolerance [25] . It may be difficult to distinguish between normal common pregnancy symptoms and mild degrees of cardiac dysfunction, requiring further evaluation and adjustments in pacing rate. Our patient began experiencing light-headedness and breathlessness with exertion, in the early second trimester. After cardiac evaluation the rate settings of the pacemaker were in creased with resolution of the patient’s symptoms.

Pregnancy is considered a pro-thrombotic state due to the increase in coagulation factors. Levels of fibrinogen (Factor I), factors VII, VIII, IX, and X all increase by 50% during pregnancy. In addition, activated protein C and S, inhibitors of coagulation, decrease during pregnancy [26] . Despite these recognized physiologic changes in pregnancy, routine anticoagulation is not typically recommended in patients with pacemakers, unless additional risk factors are identified. There have been a few cases of recurrent pulmonary emboli secondary to large thrombi formed along the pacemaker lead reported in the literature [27] [28] . Most of these cases responded well to anticoagulation with heparin when the symptoms presented. There is one reported case where the thrombi did not resolve with anticoagulation treatment, which required interventional cardiac surgery after an uncomplicated delivery [29] . Adequate data are lacking to firmly establish absolute clinical guidelines in the management of the patient with a pacemaker in place. Despite the absence of pharmacologic recommendations, prophylactic measures such as the use of pregnancy-specific support hose and avoiding situations that lead to lower extremity venous stasis should be empirically employed.

In cases where anticoagulation is required, heparin derivatives are preferred over warfarin as these former agents do not cross the placenta [30] . An exception may be in the patient with mechanical valves, where heparin use was associated with a higher incidence of valve thrombosis compared to warfarin [31] . This remains a controversy, and multiple empiric regimens have been suggested in these specific circumstances [32] . In one report, a patient on warfarin with an implanted pacemaker secondary to Ebstein’s anomaly had an intrauterine fetal demise at 20 weeks [24] . The fetal autopsy showed evidence of warfarin embryopathy [4] . Warfarin use beyond 36 weeks of gestation might also be associated with an increased risk of both maternal and fetal hemorrhage [33] .

In terms of choosing a vaginal delivery versus a caesarean section for these patients, both methods have been advocated for in case reports [34] [35] . Generally speaking, delivering with a pre-existing pacemaker is a low risk event and not a contraindication for vaginal delivery. The decision regarding route of delivery should be based on the obstetric indications or other co-morbidities associated with the pregnancy [19] [26] .

Pacemakers do not interfere with antepartum or intrapartum external fetal heart rate monitoring. This is because these are ultrasonographic modalities that do not compete electronically with the pacemaker device. During labor, internal fetal scalp electrodes are most commonly used to record fetal electrocardiographic signals. The typical fetal scalp electrode has notch filters that eliminate power line interference frequencies above 60 Hz and band-pass filters that omit frequencies <30 Hz and >100 Hz, thus allowing only frequencies between 30 - 50 Hz to be picked [36] [37] . The maternal ECG signals are below 30 Hz [38] and are therefore selectively filtered out by these device features. However, there are some reports where the scalp electrode recorded the pulse from the maternal pacemaker rather than the fetal R wave during intrapartum monitoring. This happens when the maternal pacing artifact has higher voltage than the fetal R wave, as a result, maternal ECG signals instead of fetal R waves are detected by fetal scalp electrode. For this reason, manufacturers of fetal heart rate monitors specifically note that use of their instruments require extra caution during monitoring.

The anesthetic management of a pregnant patient with a pacemaker is also important to consider for delivery management. Anesthesia consultation early during the pregnancy is advised [1] . During the first stage of labor, cardiac output can increase by 12% from the baseline value and increases even further as labor continue. At full cervical dilation cardiac output increases by an average value of 34% [39] . These changes in cardiac output can be attenuated with the use of epidural anesthesia [19] [40] . Further, performing the delivery in the lateral decubitus position is also recommended, as this position reduces rapid hemodynamic fluctuations during bearing down [41] .

In patients undergoing cesarean delivery, the anesthesiologist must be aware of mode of pacing, date of implantation and durability of the pacemaker batteries [42] . He should be able to recognize early signs of reduced cardiac output and any pacemaker dysfunction on ECG. Additionally, any electrolyte imbalance must be corrected before anesthesia as both hypokalemia or hyperkalemia can alter the pacing threshold [43] . While selecting the type of anesthesia for surgery, it is best to avoid any maternal hypotension as it can compromise uteroplacental blood flow [44] . For this reason epidural anesthesia is preferred over spinal anesthesia as latter is more often associated with maternal hypotension and subsequent fetal bradycardia [40] . This especially important in patients with pacemakers who may not generate a tachycardic response to hypotension associated with conduction anesthesia [45] . Baron et al. [46] did not find any difference in maternal heart rate before and after the epidural anesthesia. Further, adequate prior hydration and vasopressors should be used to minimize hemodynamic changes associated with regional anesthesia [42] .

During cesarean delivery, only bipolar electrocautery should be used, and in very short bursts, to avoid interference pacemaker output and inappropriate resetting of the device [47] . Inhibition of output due to interference from electrocautry may lead to asystole in a pacemaker dependent patient. Reprogramming of the pacemaker to an asynchronous mode is protective against electromagnetic interference and is generally only done for pacemaker dependent patients. If changes in pacemaker programming are made before surgery, it is important to program the device back to initial settings after surgery. As a routine precaution, the grounding plate for the cautery system should be placed as close as possible to the operating site, and as far as possible away from the pacemaker [48] [49] . If even after these measures are in place, the pacemaker is still affected by the surgical instrumentation then the pacemaker can be converted to a continuous asynchronous pacing mode (VOO) by programming or by placement of a magnet over the device. The magnet must remain in place over the device to maintain asynchronous mode of pacing.

Again, there is limited clinical information regarding adverse pregnancy outcomes associated with pacemaker usage. In one small study [19] , only one patient developed the complication of preeclampsia during the pregnancy. In another case report, a preterm birth at 30 weeks gestation occurred with neonatal acidemia [4] . Lastly, “fetal distress” was reported in a paced gravid patient of unclear etiology, with the subsequent delivery of a healthy infant via cesarean section [34] . None of these cases had similar events, or biologically plausible connections to the pacemakers themselves, suggesting a lack of direct association.

The most common non-obstetrical complication seen with the pacemaker is skin irritation and ulceration at the implantation site due to breast hypertrophy [4] [40] . Therefore, it is important to place the pacemaker in women of reproductive age at a site such as the sub-pectoral region rather then the abdomen or breast areas, which undergo skin changes during pregnancy or may be involved in procedures like cesarean sections. Being mindful of the site of pacemaker placement would also decrease the chance of pacemaker lead dislodgement or fracture, known as Twiddler’s syndrome [19] . Other recognized complications, not specifically linked to pregnancy, include chronic pain, battery failure and extra systole [50] -[52] .