Electrocardiographic changes induced by the stellate ganglion block in normal subjects

[Ultrasound-guided stellate ganglion block accelerates postoperative gastrointestinal function recovery following laparoscopic radical gastrectomy for gastric cancer]

OBJECTIVE

To explore the effects of ultrasound-guided stellate ganglion block (SGB) on perioperative stress response, gastrointestinal hormones and postoperative gastrointestinal function recovery in patients undergoing laparoscopic radical gastrectomy for gastric cancer.

METHODS

This study was conducted among 60 American Society of Anesthesiologists (ASA) class II-III patients with gastric cancer (regardless of gender, aged 35-75 years with BMI of 18.5-26 kg/m2) undergoing elective laparoscopic radical gastrectomy. The patients were randomized into experimental group (S group, n=30) and control group (NS group, n=30). In S group, SGB at the C6 level of the right cervical spine was performed under ultrasound guidance 15 min before induction of anesthesia by injection of 7 mL 0.5% ropivacaine; the patients in NS group received injections of normal saline in the same manner. Peripheral venous blood samples were collected before SGB (T1), after surgery (T2), and on the 2nd and 6th days after surgery (T3 and T4) for determination of the levels of motitin (MOT), vasoactive intestinal peptide (VIP), cortisol (COR), and blood glucose (GLU). Intraoperative usage of sufentanil, recovery rate of intestinal sounds at 36, 48, 60, 72, 84 and 96 h after operation and the time of first passage of flatus were recorded and compared between the two groups.

RESULTS

There was no significant difference in the total amount of sufentanil consumption between the two groups. Compared with those in NS group, the patients in S group had significant lower COR and VIP levels (P < 0.05) and higher MOT level (P < 0.05) at T2, T3 and T4. Glu level at T2 and T3 was also significantly lower in S group (P < 0.05). The recovery rates of intestinal sounds at 36, 48, 60, 72 and 84 h after surgery were significantly higher (P < 0.05) and the time of the first passage of flatus was earlier in S group than in NS group (P < 0.05).

CONCLUSION

In patients with gastric cancer undergoing laparoscopic radical gastrectomy, ultrasound-guided SGB can reduce postoperative stress level, promote the recovery of gastrointestinal hormone secretion, and accelerate postoperative recovery of gastrointestinal functions.

QT Prolongation in Dialysis Patients: An Epidemiological Study with a Focus on Malnutrition

BACKGROUND/AIMS

QT prolongation is a known risk factor for ventricular fibrillation and ventricular tachycardia. Therefore, more refined management is necessary to reduce sudden cardiac death secondary to such arrhythmias.

METHODS

Electrocardiographic findings were reviewed in 224 patients, and the associations of QT prolongation with various clinical parameters were examined, including the nutritional state. Correlations were also examined between QT prolongation and body composition measurements determined by multifrequency bioelectrical impedance analysis.

RESULTS

Prolongation of the corrected QT (QTc) interval over 0.44 s was seen in 140 patients (62.5%). QT prolongation was independent of age and dialysis therapy duration and was more frequent in diabetics (70.1%) than in nondiabetics (54.2%, p = 0.014) and more frequent in women (78.8%) than in men (53.5%, p < 0.001). Serum levels of albumin (p < 0.001) and Cr (p < 0.001) and the Geriatric Nutritional Risk Index (GNRI, p < 0.001) were negatively correlated with QTc interval; no significant correlation was noted with total protein, urea nitrogen, or uric acid. Negative correlations with QTc interval were found for BMI(p < 0.01), percent total body water (%TBW; p < 0.05), and percent intracellular water (%ICW; p < 0.01) but not with the percent extracellular water/TBW ratio or edema ratio. The longer the QTc interval, the lower the fat-free mass (FFM; p < 0.01) and muscle mass (MM; p < 0.01), but there was no significant correlation with percent fat.

CONCLUSION

These results suggest that QT prolongation is a common complication and is more frequent in women and diabetic patients. The decreases in serum albumin and Cr levels, GNRI, BMI, %TBW, %ICW, FFM, and MM together coincided with malnutrition and thus suggest a close relationship of QT prolongation with malnutrition. Management of QT prolongation may be achieved better in the future by understanding these biochemical and biophysical changes, particularly those regarding malnutrition.

Effects on hemodynamic variables and echocardiographic parameters after a stellate ganglion block in 15 healthy volunteers

BACKGROUND

The sympathetic nervous system has an important role in generating pain. Various pathomechanisms are involved that respond well to the application of local anesthetics (LA), for example to the stellate ganglion block (SGB).

OBJECTIVES

We wanted to know more about the effects of SGB on cardiovascular parameters.

METHODS

We included 15 healthy volunteers; another 15 healthy volunteers as a control group (sham injection of LA). In order to produce a more precise SGB, we employed only a small volume of LA (3mL), a LA with a lower permeability (procaine 1%), and a modified injection technique. Systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), and echocardiographic parameters were recorded before and after SGB. We also investigated whether there are side differences (left and right SBG).

RESULTS

At baseline all parameters were within the normal range. After performing right and left SGB DBP significantly increased (on the right side from 68.73±8.61 to 73.53±11.10, p=0.015; on the left side from 70.66±13.01 to 77.93±10.40, p=0.003). In the control group no increase in DBP was observed. No side-specific differences were found, except a significant reduction in the maximum velocity of myocardial contraction during the systole with left-sided SGB.

CONCLUSIONS

Even with our methods we could not prevent the simultaneous occurrence of a partial parasympatholytic effect. For this reason, the SGB has only minor hemodynamic effects, which is desirable as it enhances the safety of the SGB.

QTc prolongation as a useful prognostic factor in acute paraquat poisoning

BACKGROUND

Acute paraquat poisoning has a high mortality rate. Several prognostic factors have been proposed to predict the mortality risk of paraquat-poisoned patients. However, these prognostic factors are complex and some require a laboratory. Corrected QT (QTc) has been used as a prognostic factor in several clinical conditions, such as acute organophosphate poisoning. In addition, the measurement can be obtained in a reasonable amount of time.

STUDY OBJECTIVES

This study's objective was to investigate whether QTc can predict mortality in paraquat-poisoned patients.

METHODS

This was a retrospective study. Potential prognostic factors such as QTc, vital signs at admission, and certain biochemistry variables were analyzed with Cox regression analyses for their ability to predict a patient's survival from paraquat poisoning.

RESULTS

Sixty acute paraquat-poisoned patients were admitted to the emergency department during the study period. The QTc of the survival group ranged from 0.35 to 0.48 s, whereas the nonsurvivor group ranged from 0.32 to 0.63 s. The nonsurvivor group contained a higher percentage of patients with QTc prolongation (≥0.45 s) compared with the survivor group (p = 0.04). The hazard ratio of QTc prolongation for a patient's death was found to be 2.47 (95% confidence interval [CI] 1.68-5.67) in patients with a lower potassium level (<3.2 mEq/L) and 3.71 (95% CI 1.53-8.97) in patients with a higher potassium level (≥3.2 mEq/L). In addition, hyperdynamic circulation was observed upon admission of these poisoned patients.

CONCLUSION

QTc prolongation is a useful prognostic factor for predicting death in acute paraquat-poisoned patients. Cardiovascular collapse may occur in some paraquat-poisoned patients. Physicians can use QTc as an indicator of a patient's severity of poisoning and mortality risk.

Effect of interscalene brachial plexus block on heart rate variability

Background

Interscalene brachial plexus block (ISB) may be followed by cardiovascular instability. Until date, there is no clear picture available about the underlying mechanisms of ISB. In this study, we aimed to determine the changes in heart rate variability (HRV) parameters after ISB and the differences between right- and left-sided ISBs.

Methods

We prospectively studied 24 patients operated for shoulder surgery in sitting position and divided them into two respective groups: R (right-sided block = 14 pts) and L (left-sided block = 10 pts). HRV data were taken before and 30 min after the block. Ropivacaine without ephedrine was used for the ISB through an insulated block needle connected to a nerve stimulator. Statistical analysis implemented chi-square, Student's and t-paired tests. Skewed distributions were analyzed after logarithmic transformation.

Results

All the studied patients had successful blocks. Horner's syndrome signs were observed in 33.3% of the patients (R = 5/14, L = 3/10; [P = 0.769]). There were no significant differences in pre-block HRV between the groups. The application of ISB had differential effect on HRV variables: R-blocks increased QRS and QTc durations and InPNN50, while a statistical decrease was seen in InLF. L-blocks did not show any significant changes. These changes indicate a reduced sympathetic and an increased parasympathetic influence on the heart's autonomic flow after R-block.

Conclusions

Based on the obtained results we conclude that ISB, possibly through extension of block to the ipsilateral stellate ganglion, alters the autonomic outflow to the central circulatory system in a way depending on the block's side.

Stellate ganglion block: a therapeutic alternative for patients with medically refractory inappropriate sinus tachycardia?

Inappropriate sinus tachycardia (IST) is a clinical syndrome characterized by presence of non-paroxysmal tachyarrhythmia manifesting with increased resting heart rate and exaggerated or persistent response to exercise or position. When IST is intolerable and medically refractory, invasive therapies such as sinus node modification or atrioventricular node ablation with placement of permanent pacemaker are tried to control symptoms. We present a 34 year old patient with symptomatic IST unresponsive to medical therapy who underwent anesthetic block of the right and left stellate ganglia. At four month follow up the patient demonstrated sustained improvement in heart rate and reported freedom from previous symptoms.

Rationale for minimally invasive pulmonary vein isolation and partial autonomic denervation for surgical treatment of atrial fibrillation

We seek to demonstrate the rationale of a minimally invasive surgical approach to the treatment of atrial fibrillation which combines pulmonary vein antral isolation with targeted partial autonomic denervation. The literature supporting the rationale of this approach is reviewed. There is evidence-based literature that supports both pulmonary vein electrical isolation and targeted partial autonomic denervation in the treatment of atrial fibrillation. These techniques can be combined in a minimally invasive surgical approach.

Comparison of 2% mepivacaine, clipping, and radiofrequency thermocoagulation for duration and magnitude of action in peripheral arterial blood flow induced by sympathetic block in anesthetized dogs

BACKGROUND AND OBJECTIVES

Thoracic sympathetic block has recently been performed by placement of the clips on the sympathetic chain to interrupt nerve conduction. The aim of this study was to compare clipping with 2% mepivacaine and radiofrequency thermocoagulation for the potency of sympathetic block from the results of the duration and magnitude of the vasodilation effect induced by thoracic sympathetic block in dogs.

METHODS

We measured mean arterial pressure, heart rate, and right and left brachial artery blood flow (BABF) before and after thoracic sympathetic block in 24 dogs. The experimental protocol was designed as follows: (1) left thoracic sympathetic block by 1.0 mL of 2% mepivacaine (n = 8), (2) left thoracic sympathetic block by clipping (n = 8), and (3) left thoracic sympathetic block by radiofrequency thermocoagulation (n = 8).

RESULTS

Mean arterial pressure and heart rate did not change significantly throughout the study in either group. Left thoracic sympathetic block by 2% mepivacaine increased left BABF significantly from 5 to 70 mins after the block (baseline, 100%; peak at 10 mins after the block, 179% ± 33%; P < 0.01). Left thoracic sympathetic block by clipping increased left BABF significantly from 5 to 120 mins after the block (baseline, 100%; peak at 30 mins after the block, 156% ± 31%; P < 0.01). Left thoracic sympathetic block by radiofrequency thermocoagulation increased left BABF significantly from 5 to 120 mins after the block (baseline, 100%; peak at 10 mins after the block, 206% ± 31%; P < 0.01).

CONCLUSIONS

Clipping may have a same potency compared with 2% mepivacaine and a less potency compared with radiofrequency thermocoagulation in thoracic sympathetic block in dogs.

Comparison of bupivacaine, ropivacaine, and levobupivacaine in an equal dose and concentration for sympathetic block in dogs

BACKGROUND AND OBJECTIVES

The aim of this study was to compare the potency of bupivacaine, ropivacaine, and levobupivacaine in an equal dose and concentration for sympathetic block.

METHODS

We measured mean arterial pressure, heart rate (HR), and right and left brachial artery blood flow (BABF) before and after cervicothoracic sympathetic block in 24 dogs. The experimental protocol was designed as follows: (1) left cervicothoracic sympathetic block with 1.0 mL of 0.25% bupivacaine (n = 8), (2) left cervicothoracic sympathetic block with 1.0 mL of 0.25% ropivacaine (n = 8), and (3) left cervicothoracic sympathetic block with 1.0 mL of 0.25% levobupivacaine (n = 8).

RESULTS

Mean arterial pressure and heart rate did not change significantly throughout the study in either group. Left cervicothoracic sympathetic block with 0.25% bupivacaine increased left BABF significantly from 5 to 100 mins after the block (baseline, 100%; peak at 20 mins after the block, 218% +/- 48%; P < 0.01). Left cervicothoracic sympathetic block with 0.25% ropivacaine increased left BABF significantly from 5 to 100 mins after the block (baseline, 100%; peak at 10 mins after the block, 254 +/- 38%; P < 0.01). Left cervicothoracic sympathetic block with 0.25% levobupivacaine increased left BABF significantly from 5 to 80 mins after the block (baseline, 100%; peak at 20 mins after the block, 183% +/- 38%; P < 0.01).

CONCLUSIONS

Ropivacaine may induce a greater increase in vasodilation than bupivacaine and levobupivacaine at the same dose and concentration for sympathetic block in dogs.

The changes of heart rate variability after unilateral stellate ganglion block

Background

The effect of the unilateral stellate ganglion block (SGB) on cardiovascular regulation remains controversial. We wished to evaluate the changes in heart rate variability (HRV) after a unilateral stellate ganglion block in patients with head and neck pain in the present study.

Methods

Patients with head and neck pain (n = 89) were studied. HRV was determined before and after a C6 unilateral stellate ganglion block (right-sided SGB, 40; left-sided SGB, 49) using a paratracheal technique with 1% mepivacaine (6 ml).

Results

There were no significant differences in HRV indices before and after right-sided SGB. The log scale of power in the high frequency range (lnHF) was increased and ratio of power in the low frequency range (LF) to power in the high frequency range (HF) ratio was decreased after left-sided SGB.

Conclusions

These results demonstrated that left-sided SGB increased parasympathetic activities in patients with head and neck pain.

Effects of bilateral stellate ganglion block on autonomic cardiovascular regulation

BACKGROUND

Stellate ganglion block (SGB) is performed for the diagnosis and treatment of sympathetic dependent pain in the head, neck and upper limbs. However, the effects of bilateral SGB on cardiovascular and autonomic regulation remain unknown. The aim of this study was to assess the effects of bilateral SGB on cardiovascular and autonomic function by measuring heart rate variability (HRV), systolic blood pressure variability (SBPV) and spontaneous baroreflex sensitivity (SBRS).

METHODS AND RESULTS

Twenty healthy volunteers were randomly allocated to receive right or left SGB with 8 ml 1% lidocaine solution; after 20 min, the contralateral side SGB was performed. Changes in the RR interval (RRI), systolic blood pressure (SBP), HRV, SBPV and SBRS were assessed before and after bilateral SGB. The low-frequency (LF, 0.04-0.15 Hz) and high-frequency (HF, 0.15-0.4 Hz) components of HRV and SBRS decreased significantly; however, no significant changes were found in RRI, SBP and the LF and HF components of SBPV after bilateral SGB. In subjects with symptoms of vagal blockade, HRV, SBP and SBRS were significantly affected by bilateral SGB.

CONCLUSIONS

Bilateral SGB should be performed cautiously because it can reduce cardiac vagal modulation and BRS, especially for those with symptoms of vagal blockade after bilateral SGB.

Minimally invasive pulmonary vein isolation and partial autonomic denervation for surgical treatment of atrial fibrillation

OBJECTIVE

It was our goal to determine the efficacy of a minimally invasive surgical approach to the treatment of atrial fibrillation that combines pulmonary vein antral isolation with targeted partial autonomic denervation.

METHODS

Eighty-three patients underwent video-assisted bilateral pulmonary vein antral electrical isolation with confirmation of block and partial autonomic denervation. Sixty-two (41 paroxysmal, 21 persistent/long-standing persistent) patients had a follow-up of 6 months or greater. Fifty-seven of these patients had a long-term rhythm monitor at 6 months (39 paroxysmal, 18 persistent/long-standing persistent).

RESULTS

Success was defined as no episodes of atrial fibrillation greater than 15 s duration on long-term monitoring. Treatment was successful in 32 of 39 (82.1%) patients with paroxysmal atrial fibrillation and 10 of 18 (55.6%) with persistent/long-standing persistent atrial fibrillation.

CONCLUSION

Early data suggest that pulmonary vein electrical isolation combined with targeted partial autonomic denervation is a safe and efficacious approach for the treatment of paroxysmal atrial fibrillation. Techniques are being developed for the minimally invasive surgical treatment of persistent and long-standing persistent atrial fibrillation from an epicardial approach.

Evaluation of PR, RR, QT intervals and QT dispersion following stellate ganglion block in chronic shoulder-hand pain patients

Right stellate ganglion block (SGB) can increase QT interval, rate-corrected QT interval (QTc), QT dispersion (QTD), rate-corrected QTD (QTcD), and RR interval while left SGB can decrease these intervals in healthy volunteers. No such studies have been conducted in patients with chronic pain, hence this study was designed to investigate the effects of left and right SGB on these variables in chronic shoulder-hand pain patients. In this study, 28 patients with chronic shoulder-hand pain of at least 6 months duration were given right or left SGB depending on the shoulder affected. A 12-lead electrocardiogram (ECG) was recorded before the block, 30 minutes and 60 minutes after the block. PR interval, RR interval, QT interval were recorded in all 12 leads while QTc, QTD, and QTcD were calculated. Right SGB was performed in 21 patients. A significant decrease (P < 0.05) in PR interval and a significant increase (P < 0.05) in RR interval, QT interval, and QTc interval were observed. QTD showed a significant increase (P < 0.05) only at 30 minutes after right SGB. Left SGB was performed in seven patients. A significant decrease (P < 0.05) in QT interval was observed throughout the study period, while QTc showed a significant decrease (P < 0.05) only at 60 minutes after the block. We conclude that right SGB induces significant increase of QT interval, RR interval, QTc interval, QTD, and a significant decrease of PR interval while left SGB produces a significant decrease in QT and QTc intervals in patients with chronic shoulder-hand pain.

A novel technique for experimental stellate ganglion block in rats

A stellate ganglion block (SGB) is routinely performed in a clinical setting for the treatment of sympathetically maintained pain syndromes. However, the cardiovascular effects of SGB have not been well defined. The purpose of the present study was to develop a new technique of SGB in a rat model. Our new technique of SGB is a posterior percutaneous approach and uses the cartilaginous process of the C7 spinous process as a landmark. Twenty-six Sprague-Dawley female rats were divided into six groups. Group I (n = 4) underwent right sided SGB, Group II (n = 5) underwent left-sided SGB, and Group III (n = 5) underwent bilateral SGB using bupivacaine 0.25%. Three additional sham groups (n = 4 in each group) served as controls to each of the three treatment groups. Ipsilateral eyelid droop (ptosis) was observed in all animals that underwent SGB with bupivacaine. Heart rate decreased significantly for up to 45 min after bilateral SGB compared with control groups. However, this value did not change in rats after unilateral SGB. In 9 additional rats, we evaluated the accuracy of SGB by injecting methylene blue to stain the right (n = 3), left (n = 3), and bilateral SGB (n = 3). At autopsy, 11 of 12 SG were stained post-methylene blue injection. We conclude from our study that our new approach, posterior percutaneous SGB is a reliable technique that can be used for further studies.

IMPLICATIONS

We describe a new technique for stellate ganglion block in rats that may be used in future studies to investigate the role of cervical sympathetic nervous system (especially the stellate ganglion) in regulating sympathetically maintained pain and myocardial function.

An Unusual Complication of Sinus Arrest Following Right-Sided Stellate Ganglion Block: A Case Report

We present a case of a 29-year-old female patient who had presented to us for the management of her chronic right shoulder-hand pain and developed a sinus arrest following a right-sided stellate ganglion block (RSGB). This patient on receiving a diagnostic RSGB via the anterior paratracheal (C6) approach developed sinus arrest followed by apnea and unconsciousness. On institution of resuscitative measures involving tracheal intubation, positive pressure ventilation, cardiac massage, and intravenous atropine, spontaneous cardiac activity recovered in about 3 minutes. Other signs and symptoms resolved fully in a total of 10 minutes. She had persistent postural hypotension lasting for about 24 hours requiring bed rest and was discharged about 36 hours after the procedure, without any adverse sequelae. As the sinus node is supplied by the right-sided sympathetic chain, its blockade probably resulted in unopposed parasympathetic activity leading to asystole. Available evidence of the role of right stellate ganglion in regulation of cardiac electrophysiology and functioning is also discussed.

Effects of unilateral stellate ganglion block on the spectral characteristics of heart rate variability

The effect of unilateral stellate ganglion block on cardiovascular regulation remains controversial, so the present study used power spectral analysis of heart rate variability to investigate its effect on the autonomic neural control of the heart. In 20 young healthy volunteers (mean age: 25 years), heart rate variability was determined before and after unilateral stellate ganglion block (right side 11, left side 9) using 8 ml of 1% mepivacaine during supine rest. Using autoregressive spectrum analysis, power spectra were quantified by measuring the area in 3 frequency bands: high-frequency power (lnHF, parasympathetic influence) from 0.15 to 0.40 Hz, low-frequency power (lnLF, predominantly sympathetic influence) from 0.04 to 0.15 Hz, and total-frequency power (lnTF) less than 0.40 Hz. Right stellate ganglion block decreased not only the lnLF component from 6.55+/-0.84 to 5.77+/-0.47 but also the lnHF component from 4.40+/-0.95 to 3.42+/-1.12 (p<0.05). In contrast, left stellate ganglion block changed neither the lnLF nor the lnHF component. The lnTF component was also decreased significantly by right stellate ganglion block from 7.80+/-0.95 to 7.01+/-0.36 (p<0.05), but was unchanged following left stellate ganglion block. Neither right nor left stellate ganglion block induced any significant change in both the RR and corrected QT intervals. However, changes in the RR interval induced by right stellate ganglion block showed significant positive correlation with changes in lnHF (p<0.005) and lnTF (p<0.05). These results suggest that (1) autonomic innervation to the sinus node is mainly through the right-sided stellate ganglion, (2) pharmacological right-sided stellate ganglion block may attenuate not only sympathetic but also parasympathetic activity and (3) following right stellate ganglion block the decrease in both the sympathetic and parasympathetic influence on the sinus node may inconsistently counterbalance and change the RR interval.

QT interval dispersion and autonomic modulation in subjects with anxiety

This study was designed to assess Q-T interval dispersion as a marker of electrical instability in subjects with anxiety. Recent observations have shown that the presence of anxiety symptoms increases the risk of sudden death. The Kawachi anxiety questionnaire identified 29 subjects (male/female ratio 13:16) who scored 0, 22 subjects (male/female ratio 14:8) who scored 1, and 37 subjects (male/female ratio 13:24) who scored 2 or more. In all subjects we measured electrocardiographic interlead QT dispersion and autonomic function through spectral analysis of R-R interval and blood pressure variabilities and left ventricular mass. Compared with subjects who scored 0, those reporting 2 or more symptoms showed increased heart rate-corrected QT dispersion (54.9+/-1.7 ms vs. 34.9+/-3.2 ms, P<.001), sympathetic modulation (normal logarithm low-frequency power/high-frequency power 0.59+/-0.1 vs. 0.12+/-0.04, P<.05), and left ventricular mass (120.7+/-3.5 g/m2 vs. 97.9+/-2.8 g/m2, P<.001). Probably because it augments sympathetic activity, anxiety causes left ventricular mass to increase and, like hypertension, increases heart rate-corrected Q-T interval dispersion. The consequent electrical instability could be the substrate responsible for inducing fatal ventricular arrhythmias.

Use of corrected QT interval in autonomic function testing: assessment of reproducibility

QT interval duration is influenced by the autonomic nervous system and has been proposed as an additional tool in the diagnosis of diabetic autonomic neuropathy. The study aimed to assess in normal subjects the reproducibility of QT interval duration compared with that of cardiovascular tests commonly used to explore the function of the autonomic nervous system. Fifty-nine healthy subjects (31 males, 28 females; mean age 35.1 +/- 17.7 years) performed five cardiovascular tests: deep breathing test (DBT), lying to standing test (LST), Valsalva manoeuvre (VM), postural blood pressure test (PBPT) and cough test (CT). QT interval duration was measured on an electrocardiogram (ECG) registered after a 15-min rest in the supine position. Corrected QT interval (QTc) was calculated according to Bazett's formula. The QTc interval duration for each subject was expressed as the mean of the QTc calculated by two observers. Each subject was submitted to the cardiovascular test battery and the ECG twice in 1 week. The coefficient of variation (CV) was calculated to assess the reproducibility. The observed CV values were as follows: DBT 15.8%, LST 8.0%, VM 9.5%, CT 7.2%, PBPT 176%, QTc 3.4%. Our data confirm the reproducibility of heart rate cardiovascular tests: the QTc interval is a reproducible, easily measurable parameter, which has the advantage of not requiring patient cooperation.

Unilateral changes of sympathetic tone to the heart impair left ventricular function

BACKGROUND

Different regions within the left ventricle are preferentially supplied by the left or right sympathetic system. In order to characterize different influences of left vs right sympathetic lateralization on LV function, haemodynamic effects of right and left stellate ganglion stimulations (RSGS and LSGS) as well as a right sympathetic block (RSB) were compared.

METHODS

Seven alpha-chloralose anaesthetized open chest dogs were instrumented for measurement of LV pressure (tip manometers) and regional LV wall thickness (WT, sonomicrometry) in the antero-apical wall (AW, innervated by right stellate ganglion) and postero-basal wall (PW, left stellate ganglion). Timing of regional myocadial wall motion was evaluated by the phase of the first Fourier transform of the WT signals, LV asynchrony by the phase difference (phi) between both regions, and LV diastolic function by the time constant of isovolumic relaxation (tau). Measurements were performed before and after RSB (5 ml of lidocaine 1%); in 6 dogs of this group, RSGS and LSGS (4 V, 0.2 ms, 20 Hz) were performed before RSB. In order to investigate a regional inotropic stimulation without systemic effect, 6 additional dogs received intracoronary noradrenaline injections (NIC, 0.25 microgram) into the left circumflex artery perfused myocardium.

RESULTS

LSGS and NIC led to an earlier PW-motion within the cardiac cycle (phase reduction by 40.0 +/- 15.0 degree (SEM) and 55.5 +/- 11.2 degrees) and RSGS induced an earlier AW-motion (by 33.7 +/- 15.2 degrees). After RSB, AW-motion was delayed (38.1 +/- 9.2 degrees). The consequence was an asynchronous wall motion pattern after all interventions (change in phi: LSGS-64.7 +/- 18.7 degrees, RSGS 41.1 +/- 15.7 degrees, NIC -74.5 +/- 17.4 degrees, RSB -52.6 +/- 14.6 degrees), and a prolonged relaxation (tau increase: RSGS 9.4 +/- 1.9, NIC 8.3 +/- 1.5, RSB 3.7 +/- 0.8 ms).

CONCLUSION

Unilateral increases as well as decreases of sympathetic tone to the heart result in an asynchronous wall motion pattern and an impaired LV relaxation.

Does abnormal QT interval prolongation reflect autonomic dysfunction in diabetic patients? QTc interval measure versus standardized tests in diabetic autonomic neuropathy

The question as to whether the QTc interval correlates with five cardiovascular tests (deep breathing test, 30/15 ratio test, lying to standing test, cough test, and postural blood pressure test) for the diagnosis of diabetic autonomic neuropathy (DAN) was investigated in 168 (38 Type 1, 130 Type 2) consecutive outpatients (mean age 54.9 +/- 11.2 years). QT interval was measured on an ECG recorded at rest and QTc calculated according to Bazett's formula. The percentage of patients with a QTc greater than 0.440 s was: absent DAN = 11% (n = 7), probable DAN = 7% (n = 4), definite DAN = 23% (n = 12) (p < 0.05), and the mean (+/- SD) QTc values were 0.403 +/- 0.028 s, 0.405 +/- 0.023 s, and 0.421 +/- 0.026 s, respectively. A significant correlation between QTc duration and DAN score of autonomic cardiovascular test results (r = 0.34, p < 0.0001) was observed. The calculated specificity, sensitivity, positive and negative predictive values were 89%, 15%, 70% and 37%, respectively. In conclusion, QTc can be considered as an additional specific test in the assessment of diabetic autonomic neuropathy, but cannot replace the standard battery of cardiovascular tests.

Cardiovascular phase relationships to the cortical event-related potential of schizophrenic, depressed, and normal subjects

Cardiovascular phase, especially diastole, influences attention and the event-related potential (ERP) of the right hemisphere of the brain. Depression and schizophrenia are characterized by attentional deficits, unique lateralization of brain function, and deviant phase relationships of biological oscillators. In the present study, the ERP was recorded during stimulation triggered by diastole and systole in control (n = 16), depressed (n = 16), and schizophrenic (n = 9) subjects. Fifty tones were presented and subjects were instructed to count them silently. Previous findings were supported of delayed latencies and increased amplitude in depressed patients and decreased amplitudes and delayed latencies in schizophrenics. An exaggerated effect of diastole on the ERP in the right hemisphere was observed in depressed patients, however, no cardiovascular effect on the ERP was apparent in schizophrenic patients. Results suggested that heart/brain networks are tightly coupled in normal controls, perhaps "overdriven" in depressed patients, and uncoupled in schizophrenics.

QT interval prolongation predicts cardiovascular mortality in an apparently healthy population

BACKGROUND

In myocardial infarction patients, heart rate-adjusted QT interval (QTc), an electrocardiographic indicator of sympathetic balance, is prognostic for survival.

METHODS AND RESULTS

In a 28-year follow-up, the association between QTc and all-cause, cardiovascular, and ischemic heart disease mortality was studied in a population of 3,091 apparently healthy Dutch civil servants and their spouses, aged 40-65 years, who participated in a medical examination during 1953-1954. Moderate (QTc, 420-440 msec) and extensive (QTc, more than 440 msec) QTc prolongations significantly predict all-cause mortality during the first 15 years among men (adjusted respective relative risks [RRs], 1.5 and 1.7) and among women (RRs, 1.7 and 1.6). In men, cardiovascular (RRs, 1.6 and 1.8) and ischemic heart disease mortality (RRs, 1.8 and 2.1) mainly account for this association. In women, the association cannot be attributed specifically to cardiovascular and ischemic heart disease mortality. RRs for a subpopulation without any sign of heart disease at baseline are similar. The same is observed for QTc prolongation after light exercise, although in this situation most associations are not statistically significant, probably because of smaller numbers in the QTc prolongation categories.

CONCLUSIONS

Our results suggest that QTc contributes independently to cardiovascular risk. If autonomic imbalance is an important mechanism, it might be speculated that changes in life-style (e.g., with regard to physical exercise and smoking) may have a preventive impact.

Altered cardiac repolarization in some victims of sudden infant death syndrome

Abnormal prolongation of cardiac repolarization, as reflected by a long QT interval with respect to the RR interval on the electrocardiogram, is known to be associated with ventricular tachyarrhythmias. To test the hypothesis that prolonged cardiac repolarization may characterize some babies who die of sudden infant death syndrome (SIDS), we studied the dependence of the QT interval on the preceding RR interval in 10 babies with SIDS and 29 healthy control babies. We analyzed approximately 5000 pairs of QT and RR intervals in each subject over a wide range of RR intervals. We found that the QT intervals demonstrated less dependence on the preceding RR intervals in 5 of 10 babies who subsequently died of SIDS than in normal controls. No ventricular arrhythmias were observed, however, during the six-hour recording period. Our data suggest that in some babies with SIDS the ability to shorten the QT interval as the heart rate increases is impaired. These observations are consistent with the hypothesis that relatively prolonged cardiac repolarization may predispose such babies to ventricular arrhythmias.

Changes in cardiac metabolism, perfusion, ECG and plasma catecholamines during increased intracranial pressure in the pig

The effects of graded elevations of intracranial pressure (ICP) on cardiac metabolism, blood flow and electrophysiology, and plasma catecholamines were studied in eight open-chest pigs. ICP was consecutively elevated from 15 +/- 3 mmHg in the control state to 40 +/- 4, 84 +/- 4 and 152 +/- 11 mmHg. Mean arterial blood pressure and heart rate were significantly increased at the two highest ICP levels. Cardiac oxygen uptake was also increased from 2.9 +/- 0.4 ml X min-1 to a maximum of 7.1 +/- 2.0 ml X min-1, and coronary sinus blood flow increased from 49 +/- 7 to 131 +/- 35 ml X min-1 at the highest ICP level. The transmyocardial blood flow distribution was unchanged, as determined by the microspheres technique. Arterial plasma catecholamine concentrations were significantly elevated at the two highest ICP levels, but noradrenaline overflow from the heart did not increase. The high arterial adrenaline concentrations (51 +/- 25 nmol X 1(-1) at the highest ICP level) may be responsible for the cardiac stimulation seen in these experiments. No signs of ischaemia, as judged by myocardial lactate production or the relative flow distribution to the endocardium were observed. Changes in the T-wave morphology appeared in the subendocardial ECG at all ICP levels, the changes being more prominent with increasing ICP levels. It is concluded that the increase in circulating catecholamine levels, adrenaline in particular, together with an elevation of afterload cause an increase of myocardial work, which may explain the T-wave changes in the ECG which are observed upon rapid elevation of intracranial pressure.

Relation between QT interval and heart rate. applications and limitations of Bazett's formula

We studied the relationship between QT interval and RR interval when the heart rate was changed by atrial pacing, atropine, isoproterenol, and exercise in nine healthy adult males. The following results were obtained: (1) QT shortening with an increase in heart rate was minimal in atrial pacing and an equation QT = k4 square root RR was obtained from the QT-RR relationship during atrial pacing (r = 0.64, p less than 0.001); (2) shortening of QT with shortening of RR was least in atrial pacing; (3) during recovery from exercise it was largest and almost coincident with Bazett's formula; (4) Bazett's formula, therefore, is clearly applicable in the evaluation of ECGs recorded at rest or after exercise; (5) Bazett's formula can not be applied in the evaluation of an effect of some drug or maneuver on the QT when such a drug or maneuver can affect both the QT and the RR directly. The RR-dependent QT change can be estimated from the equation QT = k4 square root RR and the difference between a measured QT and the estimated RR-corrected QT would be a genuine effect of the drug or maneuver on the QT at that heart rate. We conclude that atropine, isoproterenol and exercise actually shorten the QT interval.

Long QT: good, bad or indifferent?

A survey of current literature suggests an increasing interest in both the desirable and undesirable implications of a prolonged QT interval, the former perceived to be the beneficial effect of antiarrhythmic drugs that prolong the duration of ventricular action potential, and the latter considered to be a potential marker for sudden cardiac death in patients with ischemic heart disease. In addition, there has been an increasing interest in the congenital long QT syndrome associated with an apparent dysfunction of the autonomic nervous system and serious, potentially lethal ventricular arrhythmias. Circumstantial evidence suggests that these arrhythmias are due to increased dispersion of repolarization which may be aggravated by psychologic and emotional perturbations. In this review, the associations between the long QT interval, autonomic nervous system, dispersion of repolarization, antiarrhythmic drugs and ventricular arrhythmias are examined. Attention is directed to the difficulties of accurate QT measurement, problems related to the correction of the QT interval for heart rate and sex (QTc), the wide range of normal values and the modest QT alterations after various manipulations of the autonomic nervous system. Clinical conditions associated with marked, moderate and occasional QT lengthening are listed and discussed briefly in relation to the disturbances of nervous system, dispersion of ventricular repolarization and ventricular arrhythmias. It is proposed that the absence of relevant animal models of neurogenic or psychogenic QT prolongation hinders the investigation of the neurogenic factors associated with QT lengthening. QT prolongation is most often induced by antiarrhythmic drugs and ischemic heart disease. However, it is not known whether the occurrence of torsade de pointes type of ventricular tachycardia in patients treated with antiarrhythmic drugs is related to a critical drug dose or a critical degree of QTc prolongation. There is no conclusive evidence that QT lengthening has any predictive value either during the acute phase or during convalescence after myocardial infarction. Also, a serious deficiency in current knowledge is the lack of an established relation between the prolonged QT interval and the dispersion of ventricular repolarization. It is concluded that the number of unanswered questions discussed in this review still makes it difficult to judge when a prolonged QT interval is good, bad or indifferent.