Left Ventricular Impedance Research Articles

Sporadic high pacing and shock impedance on remote monitoring in hybrid implantable cardioverter-defibrillator systems: Clinical impact and management

Sporadic high impedance values without other anomalies detected by remote monitoring of hybrid cardiac implantable electronic device systems have been described recently. The clinical significance and related hazard of this phenomenon are not fully understood. The purpose of this study was to describe the prevalence, management, and outcomes associated with hybrid implantable cardioverter-defibrillator (ICD) systems. We collected data on patients with sporadic high lead impedance alert on remote monitoring who had undergone implantation with a hybrid ICD system between January 2015 and December 2019. Pacing thresholds, sensing and impedance values, and temporal pattern of impedance values were collected by remote monitoring, at implantation, and during an in-office visit. Among 92 patients receiving a hybrid ICD, 15 (16.3%) had high impedance alert on remote monitoring (14 Boston Scientific and 1 St. Jude Medical ICD canisters paired with Medtronic or Biotronik DF-1 leads). Four patients had a cardiac resynchronization therapy-defibrillator (CRT-D), 7 a dual-chamber ICD, and 4 a single-chamber ICD. Three patients presented with high atrial lead impedance, 7 high right ventricular lead impedance, 1 high left ventricular impedance, and 2 high shock impedance values. All patients underwent follow-up by remote monitoring. Sporadic high impedance values were not associated with an adverse outcome or need for revision in all but 1 patient, who had continuously increasing pacing thresholds due to lead microfracture. In the absence of clear signs of lead fracture or connection issues, sporadic high pacing and shock impedance in hybrid implantable defibrillator systems can be safely managed by close follow-up.

Heart monitoring using left ventricle impedance and ventricular electrocardiography in left ventricular assist device patients

BackgroundPatients who develop critical arrhythmia during left ventricular assist device (LVAD) perfusion have a low survival rate. For diagnosis of unexpected heart abnormalities, new heart-monitoring methods are required for patients supported by LVAD perfusion. Ventricular electrocardiography using electrodes implanted in the ventricle to detect heart contractions is unsuitable if the heart is abnormal. Left ventricular impedance (LVI) is useful for monitoring heart movement but does not show abnormal action potential in the heart muscle.ObjectivesTo detect detailed abnormal heart conditions, we obtained ventricular electrocardiograms (v-ECGs) and LVI simultaneously in porcine models connected to LVADs.MethodsIn the porcine models, electrodes were set on the heart apex and ascending aorta for real-time measurements of v-ECGs and LVI. As the carrier current frequency of the LVI was adjusted to 30 kHz, it was easily derived from the original v-ECG signal by using a high-pass filter (cutoff: 10 kHz). In addition, v-ECGs with a frequency band of 0.1 – 120 Hz were easily derived using a low-pass filter. Simultaneous v-ECG and LVI data were compared to detect heart volume changes during the Q-T period when the heart contracted. A new real-time algorithm for comparison of v-ECGs and LVI determined whether the porcine heartbeats were normal or abnormal. Several abnormal heartbeats were detected using the LVADs operating in asynchronous mode, most of which were premature ventricle contractions (PVCs). To evaluate the accuracy of the new method, the results obtained were compared to normal ECG data and cardiac output measured simultaneously using commercial devices.ResultsThe new method provided more accurate detection of abnormal heart movements. This method can be used for various heart diseases, even those in which the cardiac output is heavily affected by LVAD operation.

Analysis of Left Ventricular Impedance in Comparison With Ultrasound Images

Cardiac monitoring of ventricular assist devices (VADs) is important for detecting heart failure risks, such as critical arrhythmia and ventricular fibrillation, and for supplying data that are useful for hemodynamic control. Specifically, impedance cardiograms (ICGs) are especially beneficial because they have no effect on the tissue or organs and can monitor various parameters simultaneously, including the heart rate and heart contractions. In this article, we measured impedance changes in porcine left ventricles using electrodes placed around the inlet and outlet cannulae of the VAD. The measured left ventricular impedance (LVI) waveform changes are caused by heart movements, such as cardiac muscle contraction and changes in blood volume as a result of heart filling and emptying. In contrast to other impedance measurements, LVI is less affected by the movement of other organs. Using a porcine model, LVIs were measured and compared with blood flow data measured with an ultrasound blood flowmeter. The ICG showed the same frequency as the animal's heart rate, and their amplitudes were closely related to cardiac output (CO). However, the waveform differed from other vital signs, such as CO, electrocardiogram, and blood pressure. Ultrasound images were used to explain the impedance waveform. In the ultrasound images, we obtained the shape and size of the animal's heart and calculated the predicted impedance data. We then compared these to the actual measured data. These results show that the impedance signal contains detailed information on heart rate and CO; these results were unaffected by the cannulae or VAD perfusion.

Anatomical factors involved in difficult cardiac resynchronization therapy procedure: a non-invasive study using dual-source 64-multi-slice computed tomography

In cardiac resynchronization therapy (CRT) procedure, left ventricular (LV) lead implantation is time consuming. In this clinical setting, no study has investigated the impact of right atrium anatomical parameters on both CRT implantation procedure duration and X-ray exposure. Additionally, only few studies have examined the coronary sinus (CS) using dual-source 64-multi-slice computed tomography (DS 64-MSCT), and its impact on CRT procedure parameters has not yet been investigated. The aim of this prospective study was to identify local anatomical predictive factors of difficult CRT implantation procedure using DS 64-MSCT. Between January and July 2010, 50 consecutive patients underwent primo CRT implantation. The patient population had a mean age of 70 ± 10 years, and was 34% female, with New York Heart Association Class 3.2 ± 0.3 heart failure, left ventricle ejection fraction 30 ± 4%, and QRS width 157 ± 30 ms. Cardiac resynchronization therapy implantation was attempted in 50 patients, and first LV lead implantation was obtained in 49 of 50 patients (98% primary success). One implantation failed (2%) due to unsuccessful LV lead implant. Procedure parameters were as follows: LV threshold, 1.4 ± 0.8 V; LV wave amplitude, 17 ± 8 mV; LV impedance, 830 ± 240 Ω; median procedure time (skin to skin), 51 min (38 min); median fluoroscopy procedure time, 11.9 min (22 min); and median LV fluoroscopic time, 10.3 min (22 min). In 10 patients (20%), procedures were difficult requiring an implantation lasting ≥ 85 min. The only predictive factor for difficult CRT implantation was the insertion level of the CS ostium (CSO), evaluated by the distance between the CSO and the bottom floor of the right atrium (14.8 ± 4 vs. 9.5 ± 4; P= 0.01). Neither the right atrium dilation nor right ventricular dysfunction was associated with difficult CRT implantation procedures. Today, despite improvements in the materials used, problems still remain in the CRT procedure. In this clinical setting, the only predictive factor for very long CRT procedures is the CSO-level insertion (located high). This anatomical anomaly identified by DS 64-MSCT prior to surgery is responsible for 20% of difficult CRT device implantation procedures.

184 Predictive factors of difficult implantation procedure in cardiac resynchronization therapy

No studies have been published regarding factors related to difficult CRT implantation procedure and primary left ventricular (LV) lead implant failure. The aim of this prospective study was twofold: (1) to evaluate the prevalence and predictive factors of prolonged CRT implantation procedure; (2) to identify the predictive factors of primary LV lead implantation failure. Between November 2008 and September 2009, 106 pts underwent primo CRT implantation. Population characteristics were a mean age of 69 ± 10 years; 28.3% female; NYHA class 3.2 ± 0.3; LVEF (29 ± 6%); QRS width 146 ± 23 ms. Primo CRT implantation was obtained in 96/106 pts (90.5% primary success). A second procedure was successfully attempted in 6/10 pts with a second more experienced operator (5.7%). Among the remaining 4 pts, 1 pt required an epicardial LV lead implantation, and the implantation was not reattempted in the other 3 pts. The overall success rate of CRT implantation was 96.2% (102/106 pts). Procedure parameters were as follows: LV threshold (1.4 ± 0.9V); LV wave amplitude (15 ± 8 mV); LV impedance (874 ± 215 Ohms); median procedure time (skin to skin), 55 min. [45–80] and median of procedure fluoroscopy time, 11 min. [6.2–29]. In 24 patients (22.6%), difficult procedures requiring 85 min of implantation duration occurred. By univariate analysis, predictive factors of difficult implantation were LV ejection fraction (25.6 ± 6 vs. 30.2 ± 8%; p = 0.02), LVEDD (72.4 ± 11 vs. 66 ± 11 mm; p = 0.01), LVESD (62 ± 12 vs. 56 ± 12 mm; p = 0.04) and the operator's experience (very experienced operator vs. less experienced operator; p = 0.006). By multivariate analysis, only primary LV lead implantation failure, LVESD and operator's experience were independently associated with difficult procedures. In this patient subset with primary LV lead implant failure (n = 10), the only independent predictive factor was the LVESV (p = 0.03). In this study, the rate of difficult CRT device implantation procedures approached 25%. Both the degree of LV dysfunction and the operator's experience were independent predictors of surgical difficulties.

Predictive factors of difficult implantation procedure in cardiac resynchronization therapy

The usefulness of cardiac resynchronization therapy (CRT) in patients with congestive heart failure is offset by its long, user-dependent, and technical procedure. No studies have been published regarding factors related to CRT implantation procedure duration and X-ray exposure. Additionally, only a few studies have investigated the predictive factors of primary left ventricular (LV) lead implant failure. The aim of this prospective study was two-fold: (i) to evaluate the prevalence and predictive factors of prolonged CRT implantation procedure and (ii) to identify the predictive factors of primary LV lead implantation failure. Between November 2008 and September 2009, 128 consecutive patients underwent CRT implantation; of these, 22 patients (17.2%) were excluded because of CRT generator replacement. Population characteristics were a mean age of 69 +/- 10 years, 28.3% female, New York Heart Association class 3.2 +/- 0.3, LV ejection fraction (LVEF; 29 +/- 6%), and QRS width 146 +/- 23 ms. Cardiac resynchronization therapy implantation was attempted in 106 patients, and first LV lead implantation was obtained in 96 of 106 patients (90.5% primary success). Ten primary implantations failed (9.5%), due to unsuccessful LV lead implants. A second procedure was successfully attempted in six patients with a second more experienced operator (5.7%). Among the remaining four patients, one patient required a surgical epicardial LV lead implantation, and the implantation was not reattempted in the other three patients. The overall success rate of CRT system implantation was 96.2% (102 of 106 patients). Procedure parameters were as follows: LV threshold (1.4 +/- 0.9 V); LV wave amplitude (15 +/- 8 mV); LV impedance (874 +/- 215 ohm); median procedure time (skin to skin), 55 min (45-80); and median of procedure fluoroscopy time, 11 min (6.2-29). In 24 patients (22.6%), difficult procedures requiring >or=85 min of implantation duration occurred. By univariate analysis, predictive factors of difficult implantation were LV ejection fraction (25.6 +/- 6 vs. 30.2 +/- 8%; P = 0.02), LV end-diastolic diameter (72.4 +/- 11 vs. 66 +/- 11 mm; P = 0.01), LV end-systolic diameter (LVESD; 62 +/- 12 vs. 56 +/- 12 mm, P = 0.04), and the operator's experience (very experienced operator vs. less experienced operator, P = 0.006). By multivariate analysis, only primary LV lead implantation failure, LVESD, and operator's experience were independently associated with difficult procedures. In this patient subset with primary LV lead implant failure (n = 10), the only independent predictive factor was the LV end-systolic volume (P = 0.03). In this study, the rate of difficult CRT device implantation procedures approached 25%. Both the degree of LV dysfunction and the operator's experience were independent predictors of surgical difficulties. Left ventricular end-systolic volume was the only independent predictor of primary LV lead implant failure.

Using a Human Cardiopulmonary Model to Study and Predict Normal and Diseased Ventricular Mechanics, Septal Interaction, and Atrio-Ventricular Blood Flow Patterns

We upgraded our human cardiopulmonary (CP) model with additional data that enables it to more accurately simulate normal physiology. We then tested its ability to explain human disease by changing two parameter values that decrease ventricular compliance, and found that it could predict many of the hemodynamic, gas exchange, and autonomic abnormalities found in patients with left ventricular diastolic dysfunction (LVDD). The newly incorporated information includes high-fidelity pressure tracings simultaneously recorded from the RV and LV of a normal human in a cardiac catheterization laboratory, Doppler echocardiographic inlet flow velocity patterns, measures of right and left ventricular impedance, and atrial volumes. The revised cardiovascular section details the hemodynamics of a normal subject to the extent that it can now explain the effects of septal compliance on ventricular interaction, the differences in left and right ventricular pressure development, and venous blood gas mixing in the right atrium. The model can isolate the highly interrelated features of normal and abnormal physiology, and simultaneously demonstrate their interaction in a manner that would be very difficult or impossible using an intact organism. It may therefore help physicians and scientists understand, diagnose, and improve their treatment of complicated cardiovascular and pulmonary diseases. It could also simulate the hemodynamic and respiratory effects of ventricular and pulmonary assist devices, and thus help with their development.

Simplified cardiac resynchronization implantation technique involving right access and a triple-guide/single introducer approach

Biventricular pacing is useful for patients with congestive heart failure but has the disadvantage of being a long, user-dependent, highly technical procedure. The purpose of this study was to simplify the procedure. The simplified technique consists of sinus (CS) venography prior to implantation, direct coronary access for the left ventricular (LV) lead without use of a left-heart delivery system, and triple-guide/one introducer cephalic vein access as the first approach in patients presenting in sinus rhythm. A cephalic cutdown was performed, and a steerable hydrophilic guidewire was introduced in the cephalic vein. A 9Fr introducer was advanced over the guidewire, and two other guides were inserted through the introducer. This technique allowed for insertion of a right ventricular lead, an LV lead, and an atrial lead. One hundred three patients were evaluated from January 2002 to September 2004. Four implants failed (3.9%). The 7Fr LV lead was successfully placed in 99 of 103 patients (96.1%) directly via the 9Fr introducer, without use of a dedicated left-heart delivery system. The final position was lateral in 59 patients, posterolateral in 33, posterior in 4, and anterolateral in 3. Sixty patients were in sinus rhythm, 13 were in atrial fibrillation, and 26 had a previous pacemaker (n = 21) or defibrillator (n = 5). Triple cephalic vein access was possible in 48 of the patients in sinus rhythm (80%). Procedure parameters were as follows: LV threshold 0.9 +/- 0.7 V, LV wave amplitude 15 +/- 8 mV, LV impedance 790 +/- 232 Omega, skin-to-skin procedure time 76 +/- 33 minutes, and fluoroscopy time 23 +/- 19 minutes. Ten complications (10.1%) occurred: 7 lead dislodgments (3 within 48 hours and 4 within 6 months) requiring repositioning (7.1%), 1 subacute local infection requiring explantation (1%), 1 phrenic nerve stimulation (1%), and 1 pneumothorax (1%). The long-term success of biventricular pacing was 93.1%. This study demonstrates that cardiac resynchronization therapy implantation can be simplified with the combined use of a steerable hydrophilic guidewire, three guides, and one introducer via a right cephalic vein, without use of a left-heart delivery system. The triple cephalic vein approach yields an 80% implant success rate for patients in sinus rhythm. The long-term success of biventricular pacing was 93.1%.

Congenital heart disease and acquired valvular lesions in pregnancy

Hintergrund: Die jahrliche Zahl schwangerer Herzfehlerpatientinnen betragt in Deutschland etwa 6 000 (jede 130. Schwangerschaft). Die voraussehbaren hamodynamischen Veranderungen in der Schwangerschaft erlauben in der Mehrzahl der Falle eine recht zuverlassige Vorhersage des Schwangerschaftsverlaufs fur Mutter und Kind. Folgende funf Aspekte sind von betrachtlicher klinischer Bedeutung. Unkorrigierte angeborene Herzfehler: Patientinnen mit nicht korrigierbaren komplexen Herzfehlern, einer nach Palliationsoperation persistierenden myokardialen Insuffizienz oder betrachtlichen pulmonalvaskularen Widerstandserhohungen sollte von einer Schwangerschaft abgeraten werden. Pratrikuspidale Kurzschlussverbindungen werden in der Schwangerschaft in aller Regel gut toleriert. In den seltenen Fallen einer deutlichen symptomatischen Verschlechterung ist der katheterinterventive Shuntverschluss heute Therapie der Wahl. Bei Patientinnen mit Ventrikelseptumdefekt oder persistierendem Ductus Botalli liegt in aller Regel ein flussbegrenzender Defekt vor, der sich im Verlauf einer Schwangerschaft meist nicht negativ auswirkt. Bei unbehandelten Aortenisthmusstenosen sind in 2,3% der Falle schwere Hypertonien, myokardiale Dekompensationen, Aortendissektionen und zerebrale Blutungen berichtet worden, deren Pravention spezifische Beratung und Therapie erfordert. Korrigierte angeborene Herzfehler: Die Gefahrdung von Mutter und Kind ist nach Korrekturoperationen einer Fallot'schen Tetralogie vom Korrekturergebnis abhangig. Das Risiko erscheint gut abschatzbar. Bei komplexen zyanotischen Vitien besteht ein deutlich erhohtes maternales Risiko bezuglich myokardialen Pumpversagens, thromboembolischer Komplikationen, komplexer Arrhythmien und Endokarditiden. Die Inzidenz fetaler Aborte, Fruhgeburten, Unreife bei der Geburt sowie kongenitaler Fehlbildungen betragt > 50%. Erworbene Herzklappenfehler: Aufgrund der Schwangerschaftsphysiologie verschlechtert sich die hamodynamische Situation bei Mitralstenosen regelhaft. Patientinnen mit Klappenoffnungsflachen < 1,5 cm2 tolerieren diese Schwangerschaftsbedingungen haufig nicht. Sind die begrenzten Moglichkeiten einer medikamentosen Therapie erschopft, ist die perkutane Ballonvalvulotomie heute Therapie der Wahl. Die in Kompetenzzentren erzielten Behandlungsergebnisse sind auserordentlich gunstig. Die schwangerschaftstypische periphere Vasodilatation und Frequenzerhohung fuhren dazu, dass die hamodynamischen Auswirkungen einer Mitral- und Aorteninsuffizienz wahrend der Schwangerschaft in aller Regel nicht aggraviert werden. Aortenklappenstenosen sind bei Schwangeren auserordentlich selten. Der transaortale Blutfluss und Gradient nehmen im Verlauf der Schwangerschaft aufgrund der relativ verlangerten Systolendauer ab. Die linksventrikulare Wandspannung nimmt dagegen zu, so dass trotz Abnahme des Gradienten eine myokardiale Dekompensation resultieren kann. Hypertrophe Kardiomyopathie: Der Verlauf gestaltet sich meist gunstig. Eine praexistente Herzinsuffizienz wird bei etwa 20% der Patientinnen in der Schwangerschaft aggraviert. Besonders schlecht toleriert werden Vorhofflimmerepisoden und supraventrikulare Tachykardien. Beide konnen Mutter und Fetus gefahrden. Orale Antikoagulation: Die moglichen Antikoagulationsstrategien sind mit einem unterschiedlich hohen maternalen und fetalen Risiko verbunden. Bei gegebener Indikation ist die ununterbrochene orale Antikoagulation mit Phenprocoumon mit dem geringsten Risiko fur die Mutter, die Beendigung jeglicher Antikoagulation mit dem geringsten Risiko fur das ungeborene Kind verbunden. Einzelentscheidungen sind schwierig und sollten in die Hand eines erfahrenen Kompetenzzentrums gegeben werden.

Improved cardiac assistance with an aortic arch balloon.

The haemodynamic effects of intra-aortic counterpulsation with normally used cylindrical and newly designed aortic arch balloons on the coronary blood flow and the performance of the normal dog heart were compared. Both balloon types resulted in a decrease of left ventricular systolic and end-diastolic pressure, systolic arterial and end-diastolic arterial pressure. The amplitude of diastolic augmentation was significantly larger with the aortic arch balloon. The carotid artery flow increased significantly more with the aortic arch balloon (36%) than with the cylindrical balloon. Pulsation in the aortic arch effected a significant decrease in left ventricular impedance (33%), which was inversely correlated with a marked increment of the stroke volume (36%). In addition, mean coronary blood flow increased during aortic arch balloon pulsation (37%). From these data, it is concluded that optimal intra-aortic balloon pulsation should be performed with large balloons close to the aortic valve. The newly designed aortic arch balloon fulfils this condition.