Catheter stimulation of cardiac parasympathetic nerves in humans: a novel approach to the cardiac autonomic nervous system

BACKGROUND

Cardiac parasympathetic nerves run alongside the superior vena cava (SVC) and accumulate particularly epicardially adjacent to the orifice of the coronary sinus (CS). In animals, these nerves can be electrically stimulated inside the SVC or CS, which results in negative chronotropic/dromotropic effects and negative inotropic effects in the atria but not the ventricles. Parasympathetic nerve stimulation (PS) with 20 Hz in the CS, however, also excites the atria, thereby inducing atrial fibrillation. The present study overcomes this limitation by applying high-frequency nerve stimuli within the atrial refractory period. Using this technique, we investigated for the first time whether neurophysiological effects similar to those in animals can be obtained in humans.

METHODS AND RESULTS

In 25 patients, parasympathetic nerves were stimulated via a multipolar electrode catheter placed in the SVC (stimulation with 20 Hz; n=14) or CS (pulsed 200-Hz stimuli; n=11). A significant sinus rate decrease and prolongation of the antegrade Wenckebach period was achieved during PS in the SVC. During PS in the CS, a graded-response prolongation of the antegrade Wenckebach interval was observed with increasing PS voltage until third-degree AV block occurred in 8 of 11 patients. The negative chronotropic/dromotropic effects started and terminated immediately after the onset and termination of PS, respectively. Atropine abolished these effects (n=11).

CONCLUSIONS

Human parasympathetic efferent nerve stimulation induces reversible negative chronotropic and dromotropic effects. PS may serve as an adjunctive tool for the diagnosis/treatment of supraventricular tachycardias and may be beneficial for ventricular rate slowing during tachycardic atrial fibrillation in patients with congestive heart failure.

Influence of superior vena caval zone condition on cyclic changes in right ventricular outflow during respiratory support

BACKGROUND

Adequate fluid resuscitation in critically ill patients undergoing mechanical ventilation remains a difficult challenge, and diastolic and systolic right ventricular (RV) changes produced by positive airway pressure are important to consider in an individual patient with inadequate circulatory adaptation during respiratory support. We hypothesized that insufficient thoracic vena cava filling, predisposing to inspiratory collapse (zone 2 condition), may transiently affect RV outflow.

METHODS

We measured beat-to-beat superior vena caval diameter and Doppler RV outflow during a routine transesophageal echocardiographic examination in 22 patients undergoing mechanical ventilation, all of whom required hemodynamic monitoring, and we calculated a collapsibility index for the superior vena cava as maximal expiratory diameter minus minimal inspiratory diameter, divided by maximal expiratory diameter.

RESULTS

In 15 patients (group 1), the collapsibility index was low (17 +/- 7%) and was associated with a moderate inspiratory decrease in RV outflow (25 +/- 17%). However, in seven patients (group 2), we observed a high collapsibility index (71 +/- 7%), which was associated with a major inspiratory decrease in RV outflow (69 +/- 14%) combined with a reduced pulmonary artery flow period. A rapid volume expansion, only performed on group 2, markedly and significantly reduced both the collapsibility index (15 +/- 12%) and the inspiratory decrease in RV outflow (31 +/- 20%).

CONCLUSION

A major inspiratory decrease in RV outflow associated with a reduced pulmonary artery flow period in a patient undergoing mechanical ventilation reflected a high collapsibility index of the thoracic vena cava, suggesting a zone 2 condition, and may be corrected by blood volume expansion.

[Investigation of fetal arrhythmias by simultaneous recording of ascending aortic and superior vena caval blood flow]

In a period of 18 consecutive months, all the foetus referred to our Foetal Cardiology Unit for investigation of arrhythmia were systematically assessed by M mode echocardiography and simultaneous recording of blood flow in the superior vena cava and the aorta (SVC/Ao). This study was undertaken to compare the performance of these two approaches. The foetus were classified into three groups according to the arrhythmia diagnosed: Group 1: irregular arrhythmias, Group 2: bradycardias, Group 3: tachycardias. A surface ECG was recorded in all the neonates in whom the arrhythmias persisted. In Group 1, including 50 cases of extrasystoles (49 atrial and 1 ventricular), M mode echo and the Doppler provided the diagnosis in 42 and 47 cases respectively. This difference was not statistically significant. Group 2 comprised four cases of bradycardia (2 blocked atrial bigeminy, 2 complete atrioventricular blocks); the two methods provided the diagnosis in all 4 cases. Group 3 comprised 11 cases including 7 supraventricular tachycardias (SVT), 2 flutter, 1 chaotic atrial rhythm and 1 ectopic junctional rhythm. Complete analysis of these arrhythmias was possible by M mode in 4 cases and by Doppler in all cases. This difference was significant. The distribution of the 7 cases of SVT with respect to the duration of the ventriculoatrial interval was possible by M mode in 2 cases and in all cases by Doppler. This was a decisive factor in the choice of antiarrhythmic therapy. The authors conclude that Doppler and M mode are two echocardiographic approaches which are equally effective in the investigation of foetal atrial extrasystoles and probably of sustained foetal bradycardia. However, Doppler recording of SVC/Ao gives a more detailed and precise diagnosis of more complex foetal arrhythmias.

[Persistent left-sided superior vena cava diagnosed after flow-directed pulmonary artery catheterization; report of a case]

We describe a case of persistent left-sided superior vena cava discovered after insertion of a pulmonary artery (PA) catheter. The diagnosis was suggested by chest X-ray after PA catheter placement and was subsequently confirmed by an echocardiograph. A 68-year-old man was admitted to our ICU because of septic shock induced by MRSA enterocolitis. In order to monitor the hemodynamic state of the patient, a PA catheter was inserted through the left subclavian vein after placement of a central venous and flexible double lumen catheters through the right internal jugular and subclavian veins, respectively. A chest X-ray showed the PA catheter passing along the left border of the heart. An echocardiograph showed the PA catheter passing through the coronary sinus into the pulmonary artery. Anesthesiologists and intensivists should be aware of the occurrence of left-sided superior vena cava in order not to mistake catheters placed in it as being in the arterial circulation or malpositioned outside of the venous circulation.

Patent foramen ovale causing position-dependent shunting in a patient, when laying down her corset

A 75-yr-old female presented with platypnoea and orthodeoxia, shortly after laying down an old and pinching corset. The injection of activated Haemaccel in the right cubital vene during transoesophageal echocardiography, in the upright position, revealed a direct blood flow from the superior caval vein at a patent foremen ovale, consequently opening it and causing a large right-to-left shunt which was calculated at 28.5%. In the supine position there was only a minimal opening of the patent foremen ovale with a calculated right-to-left shunt of 9.5%. The patent foremen ovale was successfully closed percutaneously with a CardioSEAL.

Congenital aortocaval fistula to the superior vena cava

Aortocaval fistula is a rare cause of left-to-right shunt. Common causes are congenital, traumatic, and dissecting aneurysm. We report a case of congenital aortocaval fistula to the superior vena cava, the proximal end of which was in close relation to the ostium of the right coronary artery.

Doppler velocimetry in superior vena cava provides useful information on the right circulatory function in patients with congestive heart failure

BACKGROUND

Although flow velocities curves recorded with pulsed-wave Doppler in systemic vein are known to provide functional data on the right circulatory function, little information is available on the relationship between right heart filling dynamics and right ventricular function.

METHODS

Consecutive patients with chronic heart failure due to severe systolic left ventricular dysfunction and in sinus rhythm underwent echocardiography and right heart catheterization. In the initial part of the study, the hemodynamic correlates of different flow velocity patterns recorded into the superior vena cava were evaluated in 120 patients. The accuracy of the prediction of different right heart hemodynamic profiles by means of the different venous flow patterns was then prospectively tested in a subsequent series of 86 patients.

RESULTS

The venous flow pattern was closely related to right heart hemodynamics. A normal Doppler pattern identified patients with normal right heart hemodynamics (sensitivity 86%, specificity 78%); a "predominant systolic wave" pattern identified patients with a reduced thermodilution-derived right ventricular ejection fraction (< 30%) and normal or slightly elevated right atrial pressure (< or = 8 mmHg) (sensitivity 69%, specificity 81%); a "predominant diastolic wave" pattern identified patients with a reduced right ventricular ejection fraction (< 3 0%) and elevated right atrial pressure (> 8 mmHg) (sensitivity 52%, specificity 95%). The observed and the predicted hemodynamic profiles turned out to be concordant in 80% of patients.

CONCLUSIONS

The analysis of the flow velocity pattern into the superior vena cava is a useful tool to estimate the extent of the right circulatory impairment in patients with congestive heart failure.

Transcatheter closure of large persistent left superior vena cava causing cyanosis in two patients post-Fontan operation utilizing the Gianturco Grifka vascular occlusion device

We report the successful transcatheter closure of a large persistent left superior vena cava draining into the pulmonary venous circulation causing cyanosis in two patients who had previously undergone the Fontan operation utilizing the Gianturco Grifka vascular occlusion device. Cathet Cardiovasc Intervent 2001;53:398-404.

Two- and three-dimensional echocardiographic unroofed coronary sinus

We present the 2-dimensional findings and 3-dimensional reconstruction of images from an 18-year-old patient with unroofed coronary sinus, persistent left superior vena cava, a common atrium with levoisomerism, ventricular septal defect, and double-outlet right ventricle. The left superior vena cava showed continuity with the floor of the coronary sinus. Diagnosis of the constellation of anomalies established by transesophageal reconstruction clarified the continuity of the coronary sinus with left superior vena cava and atrial wall.

Bilateral absence of the superior vena cava

Congenital anomalies of the superior vena cava are rare and often coexist with other cardiac abnormalities. In this report, we present a case of absent bilateral superior vena cava with no associated cardiac anomaly. Blood from the arms, head, and upper torso returned to the right atrium through the azygos vein and the inferior vena cava, mimicking chronic superior vena cava obstruction.

Radiologic placement of implantable chest ports in pediatric patients

OBJECTIVE

We evaluated the technical success and complications associated with radiologic placement of implantable chest ports in children for long-term central venous access.

MATERIALS AND METHODS

Between May 1, 1996 and January 11, 2000, 29 chest ports were placed in 28 children (15 girls, 13 boys; age range, 2-17 years; mean, 11.7 years). The patient's right internal jugular vein was used for access in 93% (27/29) of the procedures, and a collateral neck vein was used as a conduit to recanalize the central veins in two procedures because of bilateral jugular and subclavian vein occlusion. All procedures were performed in interventional radiology suites. Both real-time sonography and fluoroscopy were used to guide venipuncture and port insertion. Follow-up data were obtained through the clinical examination and electronic review of charts.

RESULTS

Technical success was 100%. Fourteen percent of the catheters were removed prematurely, including one catheter removed 17 days after placement because the patient's blood cultures were positive for Candida albicans. No patients experienced hematoma, symptomatic air embolism, symptomatic central venous thrombosis, catheter malposition, or pneumothorax. The median number of days for catheter use by patients was 280 days (total, 9043 days; range, 17-869 days). The rate of confirmed catheter-related infection was 14% or 0.04 per 100 venous access days. One catheter occluded after 132 days.

CONCLUSION

In pediatric patients, radiologists can insert implantable chest ports using real-time sonographic and fluoroscopic guidance with high rates of technical success and low rates of complication.

CT-guided transfemoral portocaval shunt creation

A patient with superior vena cava (SVC) occlusion presented with severe ascites and urgent transjugular intrahepatic portosystemic shunt (TIPS) was requested. The patient had a chronically occluded SVC. An alternative to classic TIPS was employed using CT guidance to traverse the left portal vein to the inferior vena cava with a small gauge needle. Fluoroscopic guidance was then used to snare a wire placed through the needle and then work from the femoral vein to create a portocaval shunt that passed through the caudate lobe. This procedure was a technical success and improved the patient's ascites.

Doppler assessment of the fetal venous system

This article describes the achievements in Doppler measurements of the fetal venous circulation with emphasis on the clinical impact of these techniques. In rhesus isoimmunization, fetal venous flow assessment gives useful information on the fetal haematologic condition and on the impact of blood transfusion. In first trimester fetuses, Doppler evaluation of the ductus venosus and umbilical vein could attribute to the detection of cardiac defects and/or chromosomal abnormalities. The inferior vena cava flow velocity waveform could be studied in cases of fetal arrhythmias to be able to diagnose the type of fetal heart rhythm disturbances. One of the more important applications of venous Doppler assessment is its use in the evaluation of the intrauterine growth retarded fetus, who is suffering from placental insufficiency. Decrease of the late diastolic flow component in the ductus venosus waveform and the presence of umbilical venous pulsations are distinct alterations, which have been detected before cardiotocogram deterioration occurs. The clinical possibilities of venous Doppler measurements are limited, and the use of the techniques requires intensive training.

Epicardial electrode insertion by means of video-assisted thoracic surgery technique

BACKGROUND

The number of patients who depend on pacemaker (PM) insertion is steadily increasing. Slovenia has two centers for PM insertion, in which 250 such procedures are performed every year. Thus, with regard to the number of procedures per year per million inhabitants, Slovenia holds a middle position in the list of countries.

METHOD

We report a patient with cardiomyopathy, complete A-V block (A-V block III) and permanent transvenous pacing lead replacements. The resulting thrombosis of the superior vena cava compelled us to insert an epicardial permanent pacing lead. Video-assisted thoracic surgery (VATS) technique was selected.

RESULTS

Surgery was safe for the patient, of 40 minutes' duration, and with minimum blood loss. The postoperative course was devoid of complications, the patient's circulation was stable, and he was able to leave the hospital one week later.

CONCLUSIONS

We believe that the choice of the thoracoscopic method of epicardial permanent pacing lead insertion is appropriate, and that the method is safe and promising as it broadens the indications for the VATS technique.

[Unusual course of a pulmonary artery catheter through a persistent superior vena cava]

We report the unusual course of a pulmonary artery catheter through a persistent left-sided superior vena cava. After left subclavian vein cannulation and downward left-sided paramediastinum course, the Swan-Ganz catheter enters the right pulmonary artery. Haemodynamic monitoring was consistent with the diagnosis of septic shock developed by this 56-year-old woman, after cephalic duodenopancreatectomy. Persistent left-sided superior vena cava occurs in 0.5% of the population and 5-10% of patients with congenital heart diseases. It drains into the right atrium through the coronary sinus in 92% of cases and is associated with an absent right superior vena cava in 20% of cases. The left-sided superior vena cava persists when the caudal part of the left anterior cardinal vein does not degenerate. A persistent left superior vena cava may be medically relevant during implantation of pacemaker leads or radiofrequency ablation, during cardiac surgery for placement of a retrograde coronary sinus cardioplegia catheter and during transjugular intrahepatic portosystemic shunt placement.

Ultrasonographic detection of very thin percutaneous central venous catheter in neonates

To assess the ability of ultrasonography to detect the tip of a very thin (0.4 mm outer diameter) percutaneous central venous catheter (PCVC) in neonates, the PCVC tip location was assessed by ultrasonography (US) and compared to the location estimated by standard radiography for 57 PCVCs in 44 neonates. Of 57 occasions, the examiner could not find the PCVC tip in three cases (5%). In the remaining 54 instances, in 87% of cases, the PCVC tip position was consistent with the location implied by skeletal landmarks on standard radiographs. On 24 occasions we also assessed catheter tip dislodgement according to flexion and extension of the infant's arm. US could detect 78% of cases of catheter tip dislodgement. The PCVC tip was sometimes visualized as a dot and parallel lines as well as mere parallel lines. In a large population of cases, US is a reliable method for detection of a thin PCVC tip. US provides precise information about the PCVC tip position in relation to vascular structure and contributes to safer positioning of the PCVC than traditional radiography alone.