Continuous monitoring of an endocardial index of myocardial contractility during head-up tilt test

Assessment of Myocardial Contractility by SonR Sensor in Patients Undergoing Cardiac Resynchronization Therapy

BACKGROUND

SonR sensor signal correlates well with myocardial contractility expressed in terms of left ventricular (LV) dP/dt max. The aim of our study was to evaluate the changes in myocardial contractility during isometric effort in heart failure patients undergoing cardiac resynchronization therapy (CRT) with right atrial SonR sensor.

METHODS

Thirty-one patients (19 men, 65 ± 7 years, LV ejection fraction [LVEF] 28% ± 5%, in sinus rhythm) were implanted with a CRT-defibrillator (CRT-D) device equipped with SonR sensor, which was programmed in VVI mode at 40 beats/min. Twenty-four hours after implantation, each patient underwent a noninvasive hemodynamic evaluation at rest and during isometric effort, including: (1) measurement of beat-to-beat endocavitary SonR signal; (2) echocardiographic assessment; and (3) continuous measurement of blood pressure with Nexfin method (BMEYE, Amsterdam, the Netherlands). The following contractility parameters were considered: (1) mean value of beat-to-beat SonR signal; (2) mean value of LV dP/dt by Nexfin system; and (3) fractional shortening (FS) by echocardiography.

RESULTS

At the third minute of the isometric effort, mean value of SonR signal significantly increased from baseline (P < 0.001). Similarly, mean value of both LV dP/dt by Nexfin and FS significantly increased compared to the resting condition (P < 0.001; P < 0.001). While in 27 (88%) patients SonR signal increased at the third minute of the isometric effort, in four (12%) patients SonR signal decreased. In these patients, both LV dP/dt by Nexfin and FS consensually decreased.

CONCLUSIONS

In CRT patients, SonR sensor is able to detect changes in myocardial contractility in a consensual way like noninvasive methods such as Nexfin system and echocardiography.

Myocardial Performance Index in Neurocardiogenic Syncope Patients

BACKGROUND

Many syncopes resulting from neural reflexes in various conditions are called neurocardiogenic syncope (NCS). We aimed to investigate the presence of left ventricular (LV) myocardial performance index (MPI) in patients with NCS, which was diagnosed with head-up tilt table test (HUTT), and the accurateness of the test in order to use it as a method in patients with NCS. Assuming the MPI as a potential cause of syncope, we assessed the Tei index with non-invasive tissue Doppler echocardiography method.

METHODS

Consecutive outpatients with a history of recurrent unexplained syncope underwent HUTT. Twenty-nine HUTT (+) patients (24 female and five male, mean age: 30 ± 15 years) as the study group and HUTT (-) 23 healthy patients (six female and 17 male, mean age: 34 ± 16 years) as the control group were included into the study. Conventional and tissue Doppler echocardiography was performed to both groups. The MPI was determined by using PW Doppler. Measurements of Doppler time intervals, according to Tei index ((isovolumic contraction time + isovolumic relaxation time)/ejection time) is calculated as (a - b/b), where "a" is the interval between cessation and onset of the mitral inflow, and "b" is the ejection time (ET) at the LV outflow.

RESULTS

When comparing the groups in terms of MPI and ET, there was significant difference between groups. Patients with NCS had significantly longer ET and lower MPI value than control group (284 ± 24 ms vs. 260 ± 24 ms, P < 0.001, respectively and 0.44 ± 0.7 vs. 0.52 ± 0.8, P < 0.001, respectively). There was no significant difference in ejection fraction between groups.

CONCLUSION

In the present study, LV MPI value decreases in patients with NCS.

The main determinant of hypotension in nitroglycerine tilt-induced vasovagal syncope

BACKGROUND

The aim of the study was to assess the main determinant of the fall in blood pressure (BP) responsible for the head-up tilt testing-induced syncope.

METHODS AND RESULTS

The study involved 200 patients (mean age 42 ± 3; 81 male) with syncope of unknown origin after the first evaluation. According to the response to the diagnostic tilt test, the population study was divided into four groups: Group I with mixed vasovagal syncope; Group II with cardioinhibitory syncope; Group III with vasodepressive syncope; Group IV: 40 patients with clinical syncope but no tilt-induced syncope. Finger arterial BP (Portapres, TNO, Amsterdam, the Netherlands) was recorded during tilt testing. Left ventricular stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR) were computed from the pressure pulsations (Modelflow, TNO, Amsterdam, the Netherlands). During syncopal phase, the TPR decreased significantly in Group III, and increased in Group I and in Group II. CO decreased in Group I and in Group II and did not change significantly in Group III. SV decreased significantly in all groups.

CONCLUSIONS

Our data showed that the arterial system appears to be the main determinant of the BP fall in vasodepressive vasovagal syncope; while the impaired constrictive response of the venous system, leading to reduced venous return to the heart, appears to be the main determinant of BP fall in mixed and cardioinhibitory vasovagal syncope.

Carotid artery pulse wave time characteristics to quantify ventriculoarterial responses to orthostatic challenge

Central blood pressure waveforms contain specific features related to cardiac and arterial function. We investigated posture-related changes in ventriculoarterial hemodynamics by means of carotid artery (CA) pulse wave analysis. ECG, brachial cuff pressure, and common CA diameter waveforms (by M-mode ultrasound) were obtained in 21 healthy volunteers (19–30 yr of age, 10 men and 11 women) in supine and sitting positions. Pulse wave analysis was based on a timing extraction algorithm that automatically detects acceleration maxima in the second derivative of the CA pulse waveform. The algorithm enabled determination of isovolumic contraction period (ICP) and ejection period (EP): ICP = 43 ± 8 (SD) ms (4-ms precision), and EP = 302 ± 16 (SD) ms (5-ms precision). Compared with the supine position, in the sitting position diastolic blood pressure (DBP) increased by 7 ± 4 mmHg ( P < 0.001) and R-R interval decreased by 49 ± 82 ms ( P = 0.013), reflecting normal baroreflex response, whereas EP decreased to 267 ± 19 ms ( P < 0.001). Shortening of EP was significantly correlated to earlier arrival of the lower body peripheral reflection wave ( r2 = 0.46, P < 0.001). ICP increased by 7 ± 7 ms ( P < 0.001), the ICP-to-EP ratio increased from 14 ± 3% (supine) to 19 ± 3% ( P < 0.001) and the DBP-to-ICP ratio decreased by 7% ( P = 0.023). These results suggest that orthostasis decreases left ventricular output as a result of arterial wave reflections and, presumably, reduced cardiac preload. We conclude that CA ultrasound and pulse wave analysis enable noninvasive quantification of ventriculoarterial responses to changes in posture.

The venous system is the main determinant of hypotension in patients with vasovagal syncope

AIMS

In patients with vasovagal syncope (VVS), a neural reflex appears the main determinant of hypotension leading to loss of consciousness; whether hypotension is mainly due to involvement of the arterial system or the venous system remains a debated issue. The aim of the present study was to assess which of these two systems is responsible for the fall in blood pressure (BP) in patients with VVS; to this end, a haemodynamic study was carried out not only before and during loss of consciousness but also during the recovery phase.

METHODS AND RESULTS

Beat-to-beat recordings of heart rate (HR), BP (volume-clamp method) and stroke volume (SV) (modelflow method), cardiac output (CO), and total peripheral resistance (TPR) were made at rest, during unmedicated tilt testing (TT) and recovery from loss of consciousness in 18 patients with a history of syncope (age 45+/-23 years) and positive response to TT. Blood pressure showed a significant fall during prodromal symptoms and a further fall at the beginning of loss of consciousness, together with a fall in SV, CO, and HR, and a slight, but significant, increase in TPR. At the beginning of recovery, BP showed a significant increase and a further increase 5 min later, together with an increase in SV, CO, and HR without significant changes in TPR.

CONCLUSION

These results suggest that in VVS the fall in BP is mainly caused by reduced venous return to the heart. The arterial system does not appear to be the main determinant of the fall of BP; however, the system appears unable to make the appropriate compensatory changes.

An implantable loop recorder study of highly symptomatic vasovagal patients: the heart rhythm observed during a spontaneous syncope is identical to the recurrent syncope but not correlated with the head-up tilt test or adenosine triphosphate test

OBJECTIVES

The aim of this study was to analyze the heart rhythm during spontaneous vasovagal syncope (VVS) in highly symptomatic patients with implantable loop recorders (ILR) and to correlate this rhythm with the heart rhythm observed during head-up tilt test (HUT).

BACKGROUND

Heart rhythm obtained during provocative condition is often used to guide therapy in VVS. To date there is no conclusive evidence that the heart rhythm observed during a positive HUT can predict heart rhythm during VVS or that the heart rhythm observed during a spontaneous syncope will be identical to the recurrent syncope.

METHODS

Twenty-five consecutive VVS patients (age 60.2 +/- 17.1 years; 14 women,) presenting with frequent syncopes (6.9 +/- 4.6 episodes/year) and a positive HUT (cardioinhibitory in 8 patients) were implanted with an ILR. Seven of them also had a positive adenosine triphosphate (ATP) test.

RESULTS

Follow-up was 17.0 +/- 3.6 months. Thirty VVS were observed in 12 patients. Nine episodes showed bradycardia of <40 beats/min or asystole; progressive sinus bradycardia preceding sinus arrest was the most frequent electrocardiographic finding. Twenty-one syncopes occurred without severe bradycardia. The heart rhythm observed during the first syncope was identical to the recurrence. No correlation was found between slow heart rate at the ILR interrogation and a cardioinhibitory HUT response (p = 1.0) or a positive ATP test (p = 1.0).

CONCLUSIONS

In highly symptomatic patients with VVS, the heart rhythm observed during spontaneous syncope does not correlate with the HUT. The heart rhythm during the first spontaneous syncope is identical to the recurrent syncope.

Myocardial Contractility and Cardiac Filling Measured by Impedance Cardiography in Patients with Nitroglycerine-Induced Vasovagal Syncope

OBJECTIVE

Increased myocardial contractility and inadequate cardiac filling leading to activation of the Bezold-Jarisch reflex were proposed as possible triggering mechanisms of vasovagal syncope (VVS). In the present study noninvasive hemodynamic measurements were performed in order to examine the role of myocardial contractility and cardiac filling in pathogenesis of VVS.

METHODS

Hemodynamic parameters were measured during head-up tilt test (HUT) by impedance cardiography in 46 patients with unexplained syncope. Myocardial contractility was measured as index of contractility (IC), acceleration index (ACI), and ejection fraction (EF). Afterload was measured as systemic vascular resistance index (SVRI) and preload was expressed as end-diastolic index (EDI). Serial measurements were done 1 minute before HUT, during HUT at 1-minute intervals, and 1 minute after completion of HUT.

RESULTS

HUT was positive in 30 patients (10 men, 20 women, mean age 36 +/- 16 years) and negative in 16 patients (8 men, 8 women, mean age 31 +/- 14 years). No significant differences were observed between HUT(+) and HUT(-) groups in hemodynamic parameters at supine rest and during HUT until the development of syncope. SVRI was lower in HUT(+) than in HUT(-) group at syncope (122.7 + 66.3 vs 185.6 + 51.4 dyn sec cm(-5)/m2, P = 0.002) and after syncope (117.0 + 61.1 vs 198.0 + 95.7 dyn sec cm(-5)/m2, P = 0.007). ACI, IC, EF, and EDI did not differ between groups at syncope. After syncope EF was higher in HUT(+) group compared to HUT(-) group (59.2 + 6.1 vs 52.7 + 9.4%, P = 0.02).

CONCLUSION

The role of increased myocardial contractility and decreased cardiac filling is not confirmed in the present study.

Direct Comparison of a Contractility and Activity Pacemaker Sensor During Treadmill Exercise Testing

There are limited data about the chronotropic capacity of the peak endocardial acceleration (PEA) sensor. This study directly compared the chronotropic function from the PEA and the activity (ACT) sensor. The study included 18 patients (age 73 +/- 7 years) with > or = 75% pacemaker-driven heart rate (HR) and a PEA sensor and 11 healthy controls (age 67 +/- 7 years) underwent a chronotropic assessment exercise protocol (CAEP) exercise test with the pacemaker patients in VVIR mode after programming the sensors in the default setting with adjustment of the upper sensor rate as an age related maximum value (220-age). The ACT sensor was externally strapped on the thorax. Achieved exercise duration for the patients and controls was, respectively, 9.2 +/- 3 vs 18.4 +/- 4 minutes (P <0.001). The maximal achieved HR with the PEA sensor was 124 +/- 25 beats/min, versus the ACT with 140 +/- 23, versus the controls with 153 +/- 26 beats/min (P <0.001 between the groups). For the PEA, ACT, and controls, the time to peak HR was, respectively, 11 +/- 3, 7 +/- 3.6, and 18 +/- 4 (P <0.001 between groups) and HR after 10 minutes recovery was, respectively, 80 +/- 20, 65 +/- 15, and 82 +/- 4 beats/min (P <0.001 between groups). The PEA sensor functions hypochonotroop during exercise programmed as a single sensor system. It is, therefore, preferable to combine the PEA sensor with an activity-based sensor in a dual sensor system. Although both groups had normal left ventricular functions, the exercise capacity of pacemaker patients is significantly lower than in the controls.

DDDR pacing driven by contractility versus DDI pacing in vasovagal syncope: a multicenter, randomized study

Recent clinical trials have shown that selected patients with recurrent vasovagal syncope (VVS) may benefit from permanent cardiac pacing. In a previous study using head-up tilt testing (HUT) the authors demonstrated that the increase in sympathetic activity preceding syncope could be sensed by a microaccelerometer located in the tip of a ventricular pacing lead and used to drive a rate adaptive pacer. They compared in a single blind randomized crossover study, DDDR pacing driven by this system, with conventional DDI pacing in patients with recurrent VVS. Twenty-three patients (age 61.8 +/- 15.2 years, 19 men) with recurrent VVS were enrolled at seven European centers and underwent implantation of a "MiniLivingD/Best" pacing system. Inclusion criteria were (1) > 6 cumulative syncopal episodes or > or = 1 syncope within 6 months of a positive HUT, and (2) a positive HUT with bradycardia. Using a crossover study design, the pacemakers were randomly programmed for two successive periods of 6 months to DDDR or DDI mode. The numbers of episodes of syncope and presyncope, and quality-of-life (QOL), were assessed at the end of each period. During the 6 months before implant, the mean number of syncopal episodes per patient was 3.2 +/- 9. During pacing in the DDDR mode, 0.09 +/- 0.29 syncope/presyncope per patient was observed, while during the DDI period 0.48 +/- 0.73 episodes per patient were reported (P < 0.05). QOL scores were 77.40 +/- 11.32 in the DDDR mode versus 74.45 +/- 14.59 in the DDI mode (NS). In patients with recurrent VVS, symptomatic recurrences were less frequent during contractility-driven DDDR pacing, than during DDI pacing. QOL was similar in the two pacing modes.