Sinus Node Function In Patients Research Articles

Prediction of Sinus Node Dysfunction in Patients with Paroxysmal Atrial Fibrillation and Sinus Pause

Background and Objectives: Sinus pause association of paroxysmal atrial fibrillation (PAP) is generally considered a sinus node dysfunction (SND) known as tachycardia-bradycardia syndrome (TBS). Cure of tachyarrhythmias in some patients with prolonged pauses on termination of tachyarrhythmia resulted in an improvement in sinus node function and/or a return to normal ranges thus avoiding the need for permanent pacing. The purpose of this study was to investigate the electrophysiological and clinical characteristics as well as their sinus node function in patients with prolonged pauses and PAP. Methods and Results: Of 1266 PAP patients undergoing radiofrequency catheter ablation (RFCA), 122 patients with pauses (>2 s) were studied. The mean maximum symptomatic prolonged pause on termination of tachycardias was 2.67 ± 1.4 s (2.0–12.6 s). SND developed in 32 patients. There was no difference between the patients with and without SND in terms of the age and sex. Patients were divided into two groups based on the intracardiac electrophysiology study after the RFCA procedure. Eleven patients (8 men, 3 women; age 30–72 years, mean 48.2 ± 9.3 years) were placed in a normal sinus node function (NSF) group, and 17 patients (12 men, 5 women; age 37–75 years, mean 62.2 ± 7.5 years) were in an SND group. There was no significant difference in gender, left atrial dimension, left ventricular ejection fraction, blood pressure, or the longest pause between the two groups. RFCA was successful in 28 patients. Electrophysiological data show that corrected sinus node recovery time (CSNRT) was 409 ± 152 ms in NSF group patients and 558 ± 178 ms in SND group before the ablation procedure (P 2 cycle lengths in 12 patients. In the multivariate analysis, prolonged pauses on termination of tachyarrhythmia, frequency of pauses, and mean heart rate after ablation were independent predictors of SND. Conclusions: (1) Catheter ablation of atrial fibrillation (AF) is effective in treating paroxysmal AF-related TBS; (2) in some patients, there is progressive improvement of sinus node function after elimination of AF, an indication that these sinus pauses may be a manifestation of tachycardia-mediated remodeling of the sinus node, and that permanent pacemaker implantation is unnecessary; (3) among the extrinsic and intrinsic causes of SND, intrinsic causes are seldom reversible and some causes of extrinsic SND may be reversible; and (4) prolonged pauses on termination of PAF, frequency of pauses (>2.0 s), and mean heart rate after ablation were independent predictive factors of SND.

Comparison of the longevity of implantable cardioverter-defibrillator devices by different manufacturers

tachycardia in patients without prior atrial surgery: electroanatomic characterization and ablation outcome. Heart Rhythm 2005;2:594–601. [12] Sanders P, Kistler PM, Morton JB, Spence SJ, Kalman JM. Remodeling of sinus node function in patients with congestive heart failure: reduction in sinus node reserve. Circulation 2004;110:897–903. [13] Sairaku A, Nakano Y, Oda N, et al. Prediction of sinus node dysfunction in patients with persistent atrial flutter using the flutter cycle length. Europace 2012;14:380–7.

Preprocedural Ventricular Rate Predicts Subsequent Sick Sinus Syndrome after Ablation for Long‐Standing Persistent Atrial Fibrillation

Concealed sick sinus syndrome may become manifest after restoration of sinus rhythm by ablation in patients with long-standing persistent atrial fibrillation (AF). The purpose of this study was to investigate the association between the preprocedural ventricular rate during AF and sinus node function in patients with long-standing persistent AF. Consecutive patients (n = 102) who underwent ablation for long-standing persistent AF were enrolled. We measured the ventricular rate during AF before ablation in the absence of antiarrhythmic drugs. Sinus node function was assessed by electrophysiological study and serial Holter recordings after ablation. Patients in the lowest quartile of ventricular rate during AF had longer corrected sinus node recovery time (1.06 ± 1.39 seconds) than those in the other quartiles (0.54 ± 0.31 seconds; P = 0.006) and lower mean heart rate on 24-hour Holter recording 3 months after ablation (68 ± 9 beats/min vs 75 ± 10 beats/min, P = 0.01). During a mean follow-up of 23 ± 10 months, sick sinus syndrome necessitating permanent pacemaker implantation developed in five (5%) patients, and multivariate analysis revealed that a low ventricular rate during AF rate was an independent risk factor for sick sinus syndrome (odds ratio = 0.90 for a 1 beat/min increase in AF rate, P = 0.04). A low preprocedural ventricular rate during AF indicates the existence of sinus node dysfunction after restoration of sinus rhythm by ablation in patients with long-standing persistent AF.

Beating to time: calcium clocks, voltage clocks, and cardiac pacemaker activity

the heartbeat arises in the sinoatrial node (SAN) and then spreads throughout the heart. SAN function is therefore essential for normal cardiac physiology. The function of the SAN decreases with age, and this has been correlated with changes of ion channel expression ([12][1]). It is therefore of

Sinus node function in patients operated for mitral valve disease: indirect evaluation with epimyocardial electrodes

To study the interatrial conduction times and atrial node performance in patients submitted to mitral valve surgery with the aid of temporary atrial epicardic electrodes. The atriograms were carried out in the first postoperative day and before the hospital discharge of ten consecutive patients. Sixty percent of the patients could complete the post-operative study protocol. The main results were: a) Post-operative arrhythmias were detected in 50% of the patients; b) There were no statistical differences between the pre and post-operative 12 lead EKGs. c) The interatrial conduction time (IACT) ranged from 90 to 140ms in the first post-operative day, and from 110 to 130ms at hospital discharge; d) The sinus node recovery time (SNRT) ranged from 250 to 560ms in the first post-operative day and from 180 to 360ms at hospital discharge; e) The sinus atrial conduction time (SACT) remained between 70 and 140ms, both in the first post-operative day and at hospital discharge, and; f) The IACT was normal in patients whose left atrium (LA) was less than 50mm in diameter but supra normal in the remaining cases. Sinus node function and inter-atrial conduction are not altered by mitral valve operation. Post-operative programmed epicardic atrial stimulation is easy and safe.

Aging and Sinoatrial Node Dysfunction

In the century since the discovery by Keith and Flack of the sinoatrial node in the mole heart, a detailed mosaic of its cellular, anatomic, and electrophysiological properties has emerged. The human sinus node has been found to be anatomically constant and well localized, occupying an approximately 10-mm subepicardial region on the sulcus terminalis at the superior cavo–atrial junction.1 Histologically, its ultrastructure of central P cells (likely corresponding to the leading pacemaker site) and outer transitional zone merging with surrounding atrial myocardium have been well characterized.1 Great progress also has been made in defining the ionic mechanisms responsible for the sinoatrial action potential and its spontaneous pacemaker activity, including important contributory roles for I Ca,L, I k, and the funny current, I f.1 This morphologically discrete, unifocal sinus node is not the exclusive force behind clinical sinus rhythm, however. Detailed animal and human mapping has demonstrated that normal cardiac pacemaker activity is widely distributed in the right atrium. In the human atrium, the pacemaker complex extends for up to 75 mm along the long axis of the sulcus terminalis and precaval band.2 At times, even left atrial pacemakers may be active during normal sinus rhythm.2 Graduated differential sensitivity to adrenergic and vagal inputs exists along the integrated pacemaker complex such that superior sites tend to dominate during periods of sympathetic drive, whereas inferior sites are activated by increased parasympathetic tone. Increasing the complexity, each sinus beat may have multicentric origin, and the nature of conduction out of the node also seems to be variable in response to autonomic tone.2 The presence of a diffuse pacemaker complex …

Issue Highlights

HomeCirculationVol. 110, No. 8Issue Highlights Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIssue Highlights Originally published24 Aug 2004https://doi.org/10.1161/circ.110.8.893Circulation. 2004;110:893REMODELING OF SINUS NODE FUNCTION IN PATIENTS WITH CONGESTIVE HEART FAILURE: REDUCTION IN SINUS NODE RESERVE, by Sanders et al.Electrophysiological and anatomic remodeling of the ventricles and atrium has been observed previously in patients with congestive heart failure, with atrial remodeling being particularly prominent in those patients with prior atrial fibrillation. The present study by Sanders et al has further defined right atrial abnormalities in patients with congestive heart failure and no prior history of atrial arrhythmias. These investigators found abnormalities both in innervated and pharmacologically denervated sinus node function in marked conduction abnormalities along the crista terminalis. These latter abnormalities were predominately related to markedly abnormal conduction that is consistent with the development of nonuniform anisotropy secondary to fibrosis in that region. These findings provide insight into the increased instance of atrial tachyarrhythmias and, in particular, atrial flutter in patients with heart failure. The anatomic and electrophysiological “barrier” of the crista terminalis is a requisite component of isthmus-dependent flutter. On the basis of the present study, the incidence of atrial fibrillation, as well as the brady-tachy syndrome in patients with congestive heart failure, can be more appropriately understood. See p 897.LEFT VENTRICULAR ASSIST DEVICE AS DESTINATION FOR PATIENTS UNDERGOING INTRAVENOUS INOTROPIC THERAPY: A SUBSET ANALYSIS FROM REMATCH (RANDOMIZED EVALUATION OF MECHANICAL ASSISTANCE IN TREATMENT OF CHRONIC HEART FAILURE), by Stevenson et al.There has been intense interest in the use of left ventricular assist devices (LVADs) as long-term destination therapy for patients with end-stage heart failure. Although the Randomized Evaluation of Mechanical Assistance in Treatment of Chronic Heart Failure (REMATCH) trial found that the use of LVADs extended survival, the absolute increment was modest. In a subset analysis of the REMATCH trial, Stevenson et al report that patients who required intravenous inotropic support at baseline had a worse prognosis with standard care than patients who did not require inotropic support, but with LVADs, both groups obtained a similar survival rate. As a result, the incremental survival benefit with LVAD was greater in patients who required inotropic support, thus identifying a subpopulation that may particularly benefit from LVAD therapy. See p 975.RELATIONSHIP BETWEEN ACTIVATED CLOTTING TIME AND ISCHEMIC OR HEMORRHAGIC COMPLICATIONS: ANALYSIS OF 4 RECENT RANDOMIZED CLINICAL TRIALS OF PERCUTANEOUS CORONARY INTERVENTION, by Brener et al.In patients undergoing coronary interventions, unfractionated heparin is monitored by the activated clotting time (ACT). The ACT that predicts both hemorrhagic complications and coronary ischemia is not known, particularly in the era of multiple platelet inhibitor use. Brener and colleagues pooled the results from 4 large studies comprising >8000 patients and found that the ACT did not correlate with ischemic complications and had a minimal association with bleeding. Increased weight-adjusted heparin dose was associated with a modest increase in rate of bleeding. Although the results would need to be validated in a prospective trial, this study suggests that the ACT provides little helpful information beyond the heparin dose. See p 994.Visit www.circ.ahajournals.org:Images in Cardiovascular MedicineLeriche Syndrome Visualized by 3-Dimensional Multislice Computed Tomography Angiography. See p e77. Download figureDownload PowerPoint Previous Back to top Next FiguresReferencesRelatedDetails August 24, 2004Vol 110, Issue 8 Advertisement Article InformationMetrics https://doi.org/10.1161/circ.110.8.893 Originally publishedAugust 24, 2004 PDF download Advertisement

Remodeling of sinus node function in patients with congestive heart failure: reduction in sinus node reserve.

Experimental and clinical studies have demonstrated diffuse atrial remodeling in congestive heart failure (CHF). We hypothesized that patients with CHF would demonstrate derangement of sinus node function. Eighteen patients with symptomatic CHF (left ventricular ejection fraction, 26+/-5%) and 18 age-matched control subjects were studied. Under autonomic blockade, the following were evaluated: intrinsic sinus cycle length, corrected sinus node recovery time (CSNRT), sinoatrial conduction time, number and duration of fractionated electograms or double potentials along the crista terminalis, and location of the earliest sinus activity. Electroanatomic mapping was performed to evaluate the location and nature of the sinus node complex, to characterize sinoatrial propagation, and to evaluate conduction abnormalities and voltage amplitude along the crista terminalis. Patients with CHF demonstrated the following findings compared with age-matched control subjects: prolongation of the intrinsic sinus cycle length (P=0.005), prolongation of CSNRT (P<0.0001), caudal localization of sinus activity both during sinus rhythm (P=0.03) and after pacing (P=0.002), prolongation of sinoatrial conduction time (P=0.02), greater number (P<0.0001) and duration (P<0.0001) of fractionated electrograms or double potentials along the crista terminalis, loss of voltage amplitude along the crista terminalis (P=0.02), and abnormal and circuitous propagation of the sinus impulse. This study demonstrates that patients with CHF have significant sinus node remodeling characterized by anatomic and structural changes along the crista terminalis with a reduction in functional sinus node reserve. This finding may have implications for the development of clinical bradycardia in CHF and for the use of negatively chronotropic agents and pacing in this condition.

P-224 Pulmonary vein isolation improves sinus node function in patients with atrial fibrillation

P-224 Pulmonary vein isolation improves sinus node function in patients with atrial fibrillation

P-224 Pulmonary vein isolation improves sinus node function in patients with atrial fibrillation

P-224 Pulmonary vein isolation improves sinus node function in patients with atrial fibrillation

Cardiorespiratory response to exercise after the Fontan operation: A serial study

Objectives. The purpose of this study was to assess whether there is deterioration of aerobic capacity over time after the Fontan operation in individual patients.Background. We previously observed that maximal aerobic capacity after the Fontan operation was lower in older patients than in younger patients. It was unclear whether this represented a decrease in aerobic capacity with time after operation or was a function of studying patients of different ages at different times postoperatively.Methods. All patients who had more than one postoperative exercise study were included. There were 25 patients (19 male, 6 female), aged 3.8 to 39 years at the time of the operation. The first exercise test was performed, on average, 2.2 years after the Fontan operation, and the last exercise test was performed, on average, 5.9 years (range 1.8 to 13) after the operation. In 11 patients, coronary sinus drainage was left on the pulmonary venous side. Five patients had had a previous Glenn operation. Exercise was performed to exhaustion with use of a 3-min incremental cycle protocol.Results. Exercise duration, oxygen uptake, blood pressure, respiratory rate, minute ventilation, pulmonary blood low index, exercise factor, ST-T wave changes and the prevalence of arrhythmias were similar during the first and last tests. Exercise systemic arterial blood oxygen saturation decreased from the first to the last postoperative test (p < 0.006) regardless of age. The percent of predicted heart rate, at rest and during maximal exercise, decreased more in older patients from the first to the last test (p < 0.05 for rest and exercise).Conclusions. In this select group of patients, exercise tolerance remained relatively unchanged over the range of 13 years after the Fontan operation. Heart rate at rest and during maximal exercise decreased more than predicted for age in older patients. A small but significant progressive decrease in systemic arterial blood oxygen saturation was found. The former might represent abnormal sinus node function in patients with functional single ventricle, and the latter might represent a tendency toward development of abnormal ventilation/perfusion patterns resulting from the development of small pulmonary arteriovenous fistulas or an effect of position of the coronary sinus postoperatively.

Assessment of sinus node function in patients with congenital long QT syndrome.

Sinus node function was evaluated in 4 patients with congenital long QT syndrome suffering from recurrent episodes of syncope and ventricular arrhythymias. Three of the 4 patients had bradycardia at rest on a 24-hour ECG. Sinus node function was examined by the atrial overdrive suppression test and the atrial premature stimulation test. Corrected sinus node recovery time (CSNRT) was prolonged in all patients. Total sinoatrial conduction time was also prolonged in 2 of the 4 patients. In all patients with abnormally high values, these values returned to normal after atropine administration, except in one patient. His prolonged CSNRT remained high after atropine administration, indicating abnormal automaticity such as that seen in sick sinus syndrome. These results show that sinus node function in congenital long QT syndrome is often associated with autonomic dysfunction, and sometimes with intrinsic disturbances of sinoatrial conduction.

Reliability of Transesophageal Pacing in the Assessment of Sinus Node Function in Patients with Sick Sinus Syndrome

The purpose of this study was to find out whether transesophageal pacing could be utilized for assessment of sinus node function in patients with sick sinus syndrome (SSS). In 17 patients with SSS (study group) we compared the results of sinus node tests obtained both in the basal state and after pharmacological autonomic blockade by endocavitary stimulation and, 24 hours later, by transesophageal pacing. In another group of 17 patients with SSS (control group), we compared the results obtained by two endocavitary studies. In "study group", sinus cycle length (SCL) and corrected sinus node recovery time (CSRT) did not show significant differences between the two studies both in the basal state and after autonomic blockade, whereas sinoatrial conduction time (SACT) was more prolonged during esophageal pacing (P less than 0.01). In "control group", sinus node measures did not show significant differences between the two studies. In the "study group," the following coefficients of correlation were obtained in the basal state; SCL, r = 0.65, CSRT, r = 0.57, SACT, r = 0.52 and after autonomic blockade: SCL, r = 0.95, CSRT, r = 0.62 and SACT, r = 0.53. In the basal state, the correlation for SCL and CSRT between the two studies was lower in the "study group" than in the "control group" (P less than 0.05), whereas after autonomic blockade the correlation for sinus node measures did not show significant differences between the two groups of patients. These data suggest that transesophageal study influences the autonomic tone regulating the sinus node; however, it is not responsible for important variations in sinus node measures.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of amiodarone on sinus node function in patients with sick sinus syndrome.

The effect of amiodarone on sinus node function has been studied in 9 patients with symptomatic sick sinus node as documented by Holter-ECG. All patients had programmable dual-chamber pacemakers. Sinus node activity was assessed by intermittently inhibiting the pacemakers before and after four weeks of oral amiodarone treatment. Sinus node function was not altered by amiodarone in 5 patients but was severely depressed in 4 patients. Thus, it is concluded that amiodarone cannot be used safely in all patients with the tachybrady syndrome for the treatment of symptomatic tachyarrhythmias without concomitant pacing.

Electrophysiologic effects of ethmozin on sinus node function in patients with and without sinus node dysfunction.

To compare the effects of ethmozin on sinus node (SN) function in the presence (9 patients) and absence (17 patients) of SN dysfunction, sinus cycle length (SCL), maximal corrected sinus recovery time (CSRT), paced cycle length yielding peak SN suppression, and indirect sinoatrial SA conduction time (SACT) were determined before and after intravenous administration of ethmozin in the dose 2 mg/kg. The mean +/- SD SCL were significantly shortened in patients with normal SN and were not changed in patients with SN dysfunction after ethmozin administration. The mean maximal CSRT was 252 +/- 72 before and 284 +/- 86 ms after ethmozin administration in patients with normal SN function (p less than 0.05). In patients with SN dysfunction (p less than 0.1) the mean maximal CSRT was found to be 1016 +/- 434 before and 2170 +/- 1756 ms after ethmozin administration. The mean SACT was 158 +/- 41 before and 174 +/- 51 ms after drug administration in patients with normal SN (p less than 0.05). Four out of nine patients with SN dysfunction developed second degree SA exit block after ethmozin administration, whereas SACT increased significantly in the remaining group of patients (180 +/- 35 to 210 +/- 32 ms; p less than 0.05). The PR, PA, AH, and HV intervals significantly lengthened and the valves of QRS and QT were not changed after ethmozin administration in either group. The conclusion is drawn that ethmozin should be administered cautiously to patients with SN dysfunction, particularly to patients with SA exit block, sinus pauses, or secondary pauses (in particular, with bradycardia-tachycardia syndrome).

Reproducibility of Electrophysiologic Parameters of Extrinsic Sinus Node Function in Patients with and without Sick Sinus Syndrome

In a group of 50 patients we investigated the daily reproducibility of the resting heart rate (RHR), the maximal corrected sinus node recovery time (CSNRTM), the pacing rate at which the CSNRTM occurred (OP), and the sinoatrial conduction time (SACT) during basal state. The study population was divided into two groups according to the presence or absence (as evidenced during the initial electrophysiologic study) of sinus node disease: group I included 35 patients with normal sinus node function, and group II included 15 patients with sick sinus syndrome. The electrophysiologic study was repeated approximately at the same hour and under similar conditions after an interval of at least two days (mean: 3.2 days for group I and 4.7 days for group II). The results showed good reproducibility with the exception of RHR in group I which slightly but significantly decreased in the second electrophysiologic study. The daily variations of the sinus node parameters appeared to be of similar levels in the two groups except for the CSNRTM; this parameter showed wide variations in single values in both groups, more marked in group II than in group I. Furthermore, if the CSNRTM and/or SACT were normal, it was likely that they would remain normal whatever the electrophysiologic status of the patient. Inversely, the change of status from abnormal to normal CSNRTM or SACT was not uncommon in patients with electrophysiologic signs of sinus node disease.

New application of direct sinus node recordings in man: assessment of sinus node recovery time.

Sinus node recovery time (SNRT) is frequently used to assess sinus node function in patients with suspected sick sinus syndrome (SSS). Although SNRT is assumed to reflect sinus node automaticity, this assumption remains unproven. The purpose of this study was (1) to test the hypothesis that SNRT in patients with and without SSS reflects sinus node automaticity, and (2) to assess the role of sinoatrial conduction time in the measurement of SNRT. A total of 16 patients (mean +/- SD age 63 +/- 9 years), seven of which had SSS, form the basis of this report. An electrogram of the sinus node was obtained for each of the 16 patients, and overdrive pacing was performed in each at cycle lengths of 1000 to 300 msec. SNRT was measured (1) on the sinus node electrogram (direct method, measuring SNRTd) as the interval from the last pacing stimulus artifact to the onset of the upstroke slope of first postpacing sinus beat and (2) on the high right atrial electrogram (indirect method, measuring SNRTi). Results were as follows: (1) The longest SNRTd was significantly shorter than the longest SNRTi (989 +/- 304 vs 1309 +/- 356 msec, p less than .001). (2) For the first postpacing sinus beat there was a significant prolongation of sinoatrial conduction time as compared with that for sinus beats before pacing (319 +/- 152 vs 99 +/- 35 msec, p less than .001). Sinoatrial conduction time normalized within 3.6 +/- 0.96 postpacing sinus beats. (3) At the pacing cycle length that resulted in the longest recovery time, sinus node depression was seen in 56% of patients, sinus node acceleration was noted in 26%, and no appreciable change in sinus node automaticity was observed in 19%. (4) Sinoatrial conduction time for the sinus beat before pacing and that for the first postpacing beat was longer in patients with SSS when compared with in patients without SSS. (5) In patients with SSS the abnormal SNRTi, when corrected for the degree of prolongation of sinoatrial conduction time for the first postpacing beat, became normal in five of six patients. We conclude that (1) SNRTi reflects both sinus node automaticity and sinoatrial conduction time, whereas SNRTd reflects sinus node automaticity, (2) overdrive atrial pacing results in marked prolongation of sinoatrial conduction time for the first postpacing beat, which is longer in patients with SSS when compared with in those without SSS, and (3) in patients with SSS the inference of abnormal sinus node automaticity on the basis of a prolonged corrected SNRTi is usually incorrect.

Latent abnormalities of sinus node function in patients with organic heart disease and normal sinus node on clinical basis

Sinus node (SN) function was analyzed in 22 patients (mean age: 46.2 +/- 12.9 years) with organic heart disease and normal SN on clinical basis (group I) and in 20 normal subjects (mean age: 43.9 +/- 15.6 years), (control group). Sinus cycle length (SCL), corrected sinus node recovery time (CSRT) and sinoatrial conduction time (SACT) were analyzed. After the control study, autonomic blockade (AB) was induced by i.v. propranolol (0.2 mg/Kg) and atropine (0.04 mg/Kg). Measurements of SCL, CSRT and SACT were then repeated. The mean SCL values were very similar in the two groups during the control state and after AB. There were no significant differences in SACTs between the two groups during the control state or after AB. On the contrary, the CSRT of group I was significantly longer than that of control group during the control state (344.8 +/- 78.9 versus 262.2 +/- 46.3 msec, P less than 0.001) and after AB (238.9 +/- 72.8 versus 166.8 +/- 39.3 msec, P less than 0.001). The analysis of real depression of SN automaticity (CSRT minus SACT) in the two groups shows that prolongation of CSRT in group I during the control study and after AB is related to an intrinsic abnormality of SN automaticity; on the contrary, no dysfunctions of the autonomic nervous system appear. These data indicate that the intrinsic abnormality of SN automaticity represents the earliest involvement of the SN in subjects with organic heart disease and normal SN on clinical basis, although this conclusion is speculative and requires experimental verification.

The role of the autonomic nervous system on sinus node function in patients with intermittent sinoatrial block

Sinus node (SN) function was analyzed with and without autonomic blockade (AB) in 31 patients (mean age: 57.6 +/- 12.8) with intermittent sinoatrial block. Twenty-one patients had organic heart disease; in the remaining ten signs of underlying heart disease were not present. Nineteen patients had dizziness or syncope. Sinus cycle length, sinus rate, corrected sinus node recovery time (CSRT) and sinoatrial conduction time (SACT) were analyzed. After control measurements, AB was produced by i.v. propranolol (0.2 mg/Kg) and atropine (0.04 mg/Kg). Measurements of electrophysiological parameters were then repeated. After AB sinus rate and CSRT did not show statistically significant differences, whereas SACT decreased significantly (P less than 0.001). When intrinsic heart rate (IHR) was abnormal (11 cases), intrinsic CSRT was always abnormal, whereas when IHR was normal, intrinsic CSRT was normal in 11 patients and abnormal in nine. In several cases, when sinus rate increased after AB, CSRT decreased and vice-versa. The parameters of intrinsic SN function were normal in 80% of patients with a normal heart and only in 14.2% of patients with organic heart disease. These data indicate that: (1) during the control period SACT is mainly conditioned by the vagal tone; (2) abnormalities in control CSRT are not uniformly abolished after AB in patients with normal IHR; (3) AB has a differential effect on the two variables of SN automaticity; i.e. sinus rate and CSRT; and (4) in patients without underlying heart disease, the SN dysfunction is almost exclusively related to alterations of the autonomic nervous system.

Electrophysiological effects of glucose-insulin-potassium on sinus node function in patients with and without sinus node dysfunction.

The electrophysiological effects of glucose (100 g)-insulin (20 U)-potassium (10 mmol X litre-1) infusion (GIK) on three parameters of sinus node function were studied in 14 control subjects (mean age 53 +/- 14 yr) and 11 patients (mean age 50 +/- 17 yr) with sinus node dysfunction (SND). In a first series of experiments the response to GIK was examined in nine control and 11 SND patients. Following GIK, the mean spontaneous cycle length decreased by 17% (671 to 560 ms; P less than 0.01) in the control group and by 33% (1066 to 715 ms; P less than 0.001) in the SND patients; this difference between both groups was statistically significant (P less than 0.01). In the control group mean corrected sinus node recovery time (CRST) and calculated sinoatrial conduction time (SACT; n = 6) were not significantly altered after GIK. In SND patients GIK decreased the mean value of CSRT by 40% (693 to 416 ms; P less than 0.05) and of calculated SACT (n = 6) by 27% (130 to 95 ms; P less than 0.05); prolonged secondary pauses following termination of rapid atrial pacing in SND patients were also shortened. In a second series of experiments, mannitol (100 g, iv) was administered in five control patients but had no significant effect on the electrophysiological parameters tested. Plasma levels of glucose were significantly increased, by 500% (P less than 0.01), after GIK; plasma potassium and sodium concentrations decreased by 7 and 5% (P less than 0.05). The results indicate that GIK had a beneficial effect on sinus node dysfunction.