Arrhythmic Patterns Research Articles

Temporary Pacing in the Correction of Drug-Induced Bradycardia

Objective: to reduce the risk from surgical treatment in geriatric cancer patients with severe concomitant cardiovascular (CV) diseases through the differentiated intra- and postoperative use of pacing technologies for correction of life-threatening cardiac rhythm and conduction disturbances. Subjects and methods. Two hundred and eight patients (mean age 72.0±5.8 years) receiving pulse-reducing cardiotropic therapy to compensate for CV disorders, who had undergone extensive radical surgical interventions for abdominal and small pelvic malignancies of mainly Stage III (mean duration 4.2±1.6 hours) under multimodal general anesthesia, were examined. A pacing technique was chosen depending on the pattern of arrhythmia and antrioventricular (AV) block. Results. During CV therapy, bradycardia at a heart rate of 44 to 57 beats per min was identified in 71 (34.1%) patients. Perioperative pacing correction of bradycardia was required in 58 (27.9%) patients, of them 46 had no AV conduction disturbances, which permitted the use of transesophageal atrial pacing (TEAC). Endocardial pacing was performed in 12 patients with impaired AV conduction and bradysystole in the presence of persistent atrial fibrillation during and early after surgery. In the postoperative period, it was necessary to continue long-term (more than 20 hours) TEAC in the asynchronous mode in 7 patients. Extensive surgical interventions of the planned volume were made in all the patients being examined. None patient had any CV events, including pacing complications. Conclusion. Temporary pacing techniques are effective in correcting critical circulatory disorders during surgical treatment in elderly patients with persistent drug-induced bradycardia when they are treated with cardiotropic drugs.

Audiovisual Temporal Correspondence Modulates Human Multisensory Superior Temporal Sulcus Plus Primary Sensory Cortices

The brain should integrate related but not unrelated information from different senses. Temporal patterning of inputs to different modalities may provide critical information about whether those inputs are related or not. We studied effects of temporal correspondence between auditory and visual streams on human brain activity with functional magnetic resonance imaging (fMRI). Streams of visual flashes with irregularly jittered, arrhythmic timing could appear on right or left, with or without a stream of auditory tones that coincided perfectly when present (highly unlikely by chance), were noncoincident with vision (different erratic, arrhythmic pattern with same temporal statistics), or an auditory stream appeared alone. fMRI revealed blood oxygenation level-dependent (BOLD) increases in multisensory superior temporal sulcus (mSTS), contralateral to a visual stream when coincident with an auditory stream, and BOLD decreases for noncoincidence relative to unisensory baselines. Contralateral primary visual cortex and auditory cortex were also affected by audiovisual temporal correspondence or noncorrespondence, as confirmed in individuals. Connectivity analyses indicated enhanced influence from mSTS on primary sensory areas, rather than vice versa, during audiovisual correspondence. Temporal correspondence between auditory and visual streams affects a network of both multisensory (mSTS) and sensory-specific areas in humans, including even primary visual and auditory cortex, with stronger responses for corresponding and thus related audiovisual inputs.

Left Stellate Ganglion and Vagal Nerve Activity and Cardiac Arrhythmias in Ambulatory Dogs With Pacing-Induced Congestive Heart Failure

The purpose of this study was to determine the patterns of autonomic nerve activity in congestive heart failure (CHF). The relationship between autonomic nerve activity and cardiac arrhythmias in CHF is unclear. We implanted radiotransmitters in 6 dogs for continuous (24/7) simultaneous monitoring of left stellate ganglion nerve activity (SGNA), vagal nerve activity (VNA), and electrocardiography before and after pacing-induced CHF. Congestive heart failure increased both SGNA and VNA. The SGNA but not VNA manifested a circadian variation pattern. There was extensive sinus node fibrosis. We analyzed 2,263 episodes of prolonged (>3 s) sinus pauses (PSP) and 1,420 long (>10 s) episodes of paroxysmal atrial tachycardia (PAT). Most (95.3%) PSP episodes occurred at night, and 56% were preceded by a short burst of SGNA that induced transient sinus tachycardia. Long PAT episodes were typically (83%) induced by simultaneous SGNA and VNA discharge, followed by VNA withdrawal. Premature ventricular contractions and ventricular tachycardia were preceded by elevated SGNA. The reduction of sympathovagal balance at night in ambulatory dogs was due to reduced sympathetic discharge rather than a net increase of vagal discharge. The tachybrady syndrome in CHF might be triggered by an intermittent short burst of SGNA that resulted in tachycardia and sinus node suppression. Simultaneous sympathovagal discharge is a cause of long PAT episodes. These data indicate that there is an association between the specific patterns of autonomic nerve discharges and cardiac arrhythmia during CHF.

Prediction of sudden death in heart failure patients: a novel perspective from the assessment of the peak ectopy rate

In patients with heart failure (HF), the association between sudden death and arrhythmic pattern at 24-h Holter monitoring [number of ventricular premature contractions per hour (VPCs/h) and presence of non-sustained ventricular tachycardia (NSVT)] has previously been investigated with conflicting results. Since both VPCs/h and NSVT disregard the time course of arrhythmic events, we developed a new index based on the short-term peak rate of ectopies and investigated its prognostic power in HF patients. We studied 200 HF patients in sinus rhythm [age: [median (interquartile range)] 54 years [47-58], left ventricular ejection fraction (LVEF): 23% [19-28], New York Heart Association (NYHA) class II-III: 88%]. For each patient, the Holter recording was automatically scanned shifting a 30 beat window one beat at a time, and the maximum number of ectopic beats found in a window was named peak ectopy rate (PEAK_ER). The association between PEAK_ER and sudden death was assessed by Cox proportional hazards regression analysis. Survival analysis was also carried out adjusting for NYHA class, aetiology, LVEF, left ventricular end diastolic diameter, blood urea nitrogen, amiodarone, Digoxin, beta-blockers, NSVT, VPCs/h, and the standard deviation of all normal-to-normal beats. During a 5-year follow-up [31 (12-60) months], 23 patients died of sudden death. Out of the arrhythmic markers, PEAK_ER but not VPCs/h and NSVT was significantly associated with sudden death in univariable analysis (RR: 1.08, 95% CI: 1.02-1.14, P = 0.005) and after adjustment for covariates (RR: 1.09, 95% CI: 1.03-1.15, P = 0.004). The investigation of the time course of arrhythmic events provides independent information in the identification of patients at increased risk of sudden death and may therefore be considered in the development of treatment strategies in HF patients.

Interaction between hindbrain and spinal networks during the development of locomotion in zebrafish

Little is known about the role of the hindbrain during development of spinal network activity. We set out to identify the activity patterns of reticulospinal (RS) neurons of the hindbrain in fictively swimming (paralyzed) zebrafish larvae. Simultaneous recordings of RS neurons and spinal motoneurons revealed that these were coactive during spontaneous fictive swim episodes. We characterized four types of RS activity patterns during fictive swimming: (i) a spontaneous pattern of discharges resembling evoked high-frequency spiking during startle responses to touch stimuli, (ii) a rhythmic pattern of excitatory postsynaptic potentials (EPSPs) whose frequency was similar to the motoneuron EPSP frequency during swim episodes, (iii) an arrhythmic pattern consisting of tonic firing throughout swim episodes, and (iv) RS cell activity uncorrelated with motoneuron activity. Despite lesions to the rostral spinal cord that prevented ascending spinal axons from entering the hindbrain (normally starting at approximately 20 h), RS neurons continued to display the aforementioned activity patterns at day 3. However, removal of the caudal portion of the hindbrain prior to the descent of RS axons left the spinal cord network unable to generate the rhythmic oscillations normally elicited by application of N-methyl-d-aspartate (NMDA), but in approximately 40% of cases chronic incubation in NMDA maintained rhythmic activity. We conclude that there is an autonomous embryonic hindbrain network that is necessary for proper development of the spinal central pattern generator, and that the hindbrain network can partially develop independently of ascending input.

Daily and circadian expression of cryptochrome during the ontogeny of crayfish

Cryptochromes (CRY) are proteins with a dual role in the circadian function of different animals, participating in phototransduction and light signaling to the clock and as a transcriptional repressor that provides negative feedback in the clock feedback loop. Here we characterize functional expression of CRY as a marker of the functionality of the circadian pacemaker of crayfish (Procambarus clarkii) throughout post-embryonic development. Using different experimental light protocols and by means of immunofluorescence and biochemical methods, we report that, as in the adult, in young crayfish from the first embryonic stage CRY is present in cells adjacent to the eyestalk hemiellipsoidal body and the anterior margin of the brain protocerebrum. In the brain, CRY cycles after 72 h darkness, entraining to LD cycles. Meanwhile, as in the adult eye, in juveniles CRY is driven by light, showing an arrhythmic pattern in DD and cycling under LD. These results, as well as the completely different period length found in the brain circadian oscillations of 2nd post-embryonic stage and juvenile animals, suggest important changes in the properties of the crayfish pacemaker through the development. Therefore these data support a previous idea about the functionality of the circadian system from hatching.

Diagnosis and treatment of catecholaminergic polymorphic ventricular tachycardia

Catecholaminergic polymorphic ventricular tachycardia (VT) was first described by Reid et al 1 Reid D.S. Tynan M. Braidwood L. Fitzgerald G.R. Bidirectional tachycardia in a child A study using His bundle electrography. Br Heart J. 1975; 37: 339-344 Crossref PubMed Scopus (138) Google Scholar in 1975 and by Coumel et al in 1978. The condition was described as a familial cardiac arrhythmia that occurs in patients with structurally normal heart and causes exercise-/emotion-triggered syncope and sudden death with a distinctive pattern of ventricular and supraventricular arrhythmias. Since the first ryanodine receptor mutations were identified in 2001, 2 Priori S.G. Napolitano C. Tiso N. Memmi M. Vignati G. Bloise R. Sorrentino V. Danieli G.A. Mutations in the cardiac ryanodine receptor gene (hRyR2) underlie catecholaminergic polymorphic ventricular tachycardia. Circulation. 2001; 103: 196-200 Crossref PubMed Scopus (1135) Google Scholar it appeared evident that catecholaminergic polymorphic VT was caused by uncontrolled Ca2+ release from the sarcoplasmic reticulum. 3 Jiang D. Xiao B. Yang D. Wang R. Choi P. Zhang L. Cheng H. Chen S.R. RyR2 mutations linked to ventricular tachycardia and sudden death reduce the threshold for store-overload-induced Ca2+ release (SOICR). Proc Natl Acad Sci U S A. 2004; 101: 13062-13067 Crossref PubMed Scopus (350) Google Scholar Subsequent experimental studies demonstrated that such abnormal calcium handling caused arrhythmias mediated by delayed afterdepolarizations and triggered activity. 4 Liu N. Colombi B. Memmi M. Zissimopoulos S. Rizzi N. Negri S. Imbriani M. Napolitano C. Lai F.A. Priori S.G. Arrhythmogenesis in catecholaminergic polymorphic ventricular tachycardia Insights from a RyR2 R4496C knock-in mouse model. Circ Res. 2006; 99: 292-298 Crossref PubMed Scopus (261) Google Scholar This article reviews the current knowledge of the diagnosis and therapy for catecholaminergic polymorphic VT and outlines the open issues to be addressed in order to reduce the burden of life-threatening cardiac events in patients with this lethal disorder.

Electrocardiographic Abnormalities in Cardiac Contusion: Experimental Study

Objective: to study the incidence and pattern of cardiac arrhythmias and other abnormalities in the early posttraumatic period of experimental cardiac contusion and to assess their contribution to death and the development of posttraumat-ic myocardial dysfunction. Materials and methods: experiments were carried out on non-inbred albino male rats anesthetized with sodium thiopental. An electrocardiogram, respiration rate, and left carotid blood pressure were recorded in the direct fashion. Cardiac contusion was reproduced by an original device that imitated a blow of the steering wheel to the anterior chest, as that observed when a moving car clashed against an obstacle. Some animals were traumatized after preadministration of atropine sulfate. Results: sinus bradycardia accompanied by bradypnoea or short-term apnoea and lowered blood pressure is a compulsory and persistent ECG abnormality. Preinjection of atropine significantly prevents the occurrence of these changes and points to the likely reflectory mechanism of their development. Other ECG abnormalities (heterotopic rhythms, premature beats, conduction blockade, terminal ventricular complex changes, etc.) are encountered in a variety of combinations, including those among which typical changes that are undetectable, are diverse, short-term, and labile. Among them, there are virtually no hemodynamic and potentially fatal arrhythmias. Conclusion: in experimental isolated cardiac contusion, the pattern of cardiac arrhythmias differs from that observed in the inpatient setting. Cardiac arrhythmias and other ECG abnormalities do not make a considerable contribution to a mortality rate under the conditions of this experiment since there are no hemodynamic ones.

Evaluation of fetal arrhythmias from simultaneous pulsed wave Doppler in pulmonary artery and vein

Objective:To evaluate the clinical application of simultaneous recordings of pulsed wave Doppler (PWD) signals in pulmonary artery and vein as alternative sampling site for assessment of arrhythmias in the fetus.Design:Prospective,...

Arrhythmogenesis in the Developing Heart During Anoxia‐Reoxygenation and Hypothermia‐Rewarming: An In Vitro Model

The spatio-temporal pattern of arrhythmias in the embryonic/fetal heart subjected to a transient hypoxic or hypothermic stress remains to be established. Spontaneously beating hearts or isolated atria, ventricles, and conotruncus from 4-day-old chick embryos were subjected in vitro to 30-minute anoxia and 60-minute reoxygenation. Hearts were also submitted to 30-minute hypothermia (0-4 degrees C) and 60-minute rewarming. ECG disturbances and alterations of atrial and ventricular electromechanical delay (EMD) were systematically investigated. Baseline functional parameters were stable during at least 2 hours. Anoxia induced tachycardia, followed by bradycardia, atrial ectopy, first-, second-, and third-degree atrio-ventricular blocks and, finally, transient electromechanical arrest after 6.8 minutes, interquartile ranges (IQR) 3.1-16.2 (n = 8). Reoxygenation triggered also Wenckebach phenomenon and ventricular escape beats. At the onset of reoxygenation QT, PR, and ventricular EMD increased by 68%, 70%, and 250%, respectively, whereas atrial EMD was not altered. No fibrillations, no ventricular ectopic beats, and no electromechanical dissociation were observed. Arrhythmic activity of the isolated atria persisted throughout anoxia and upon reoxygenation, whereas activity of the isolated ventricles abruptly ceased after 5 minutes of anoxia and resumed after 5 minutes of reoxygenation. During hypothermia-rewarming, cardiac activity stopped at 17.9 degrees C, IQR 16.2-20.6 (n = 4) and resumed at the same temperature with no arrhythmias. All preparations fully recovered after 40 minutes of reoxygenation or rewarming. In the embryonic heart, arrhythmias mainly originated in the sinoatrial tissue and resembled those observed in the adult heart. Furthermore, oxygen readmission was by far more arrhythmogenic than rewarming and the chronotropic, dromotropic, and inotropic effects were fully reversible.

Arabidopsis FHY3 Specifically Gates Phytochrome Signaling to the Circadian Clock

Circadian gating of light signaling limits the timing of maximum responsiveness to light to specific times of day. The fhy3 (for far-red elongated hypocotyl3) mutant of Arabidopsis thaliana is involved in independently gating signaling from a group of photoreceptors to an individual response. fhy3 shows an enhanced response to red light during seedling deetiolation. Analysis of two independent fhy3 alleles links enhanced inhibition of hypocotyl elongation in response to red light with an arrhythmic pattern of hypocotyl elongation. Both alleles also show disrupted rhythmicity of central-clock and clock-output gene expression in constant red light. fhy3 exhibits aberrant phase advances under red light pulses during the subjective day. Release-from-light experiments demonstrate clock disruption in fhy3 during the early part of the subjective day in constant red light, suggesting that FHY3 is important in gating red light signaling for clock resetting. The FHY3 gating function appears crucial in the early part of the day for the maintenance of rhythmicity under these conditions. However, unlike previously described Arabidopsis gating mutants that gate all light signaling, gating of direct red light-induced gene expression in fhy3 is unaffected. FHY3 appears to be a novel gating factor, specifically in gating red light signaling to the clock during daytime.

The Legacy of the CE and BMET: Safer Healthcare Technologies

The Legacy of the CE and BMET: Safer Healthcare Technologies

Perception of Atrial Fibrillation Before and After Radiofrequency Catheter Ablation

The objective of this study was to assess the incidence and impact of asymptomatic arrhythmia in patients with highly symptomatic atrial fibrillation (AF) who qualified for radiofrequency (RF) catheter ablation. In this prospective study, 114 patients with at least 3 documented AF episodes together with corresponding symptoms and an ineffective trial of at least 1 antiarrhythmic drug were selected for RF ablation. With the use of CARTO, circumferential lesions around the pulmonary veins and linear lesions at the roof of the left atrium and along the left atrial isthmus were placed. A continuous, 7-day, Holter session was recorded before ablation, right after ablation, and after 3, 6, and 12 months of follow-up. During each 7-day Holter monitoring, the patients recorded quality and duration of any complaints by using a detailed symptom log. More than 70,000 hours of ECG recording were analyzed. In the 7-day Holter records before ablation, 92 of 114 patients (81%) had documented AF episodes. All episodes were symptomatic in 35 patients (38%). In 52 patients (57%), both symptomatic and asymptomatic episodes were recorded, whereas in 5 patients (5%), all documented AF episodes were asymptomatic. After ablation, the percentage of patients with only asymptomatic AF recurrences increased to 37% (P<0.05) at the 6-month follow-up. An analysis of patient characteristics and arrhythmia patterns failed to identify a specific subset who were at high risk for the development of asymptomatic AF. Even in patients presenting with highly symptomatic AF, asymptomatic episodes may occur and significantly increase after catheter ablation. A symptom-only-based follow-up would substantially overestimate the success rate. Objective measures such as long-term Holter monitoring are needed to identify asymptomatic AF recurrences after ablation.

36 Paroxysmal atrial fibrillation: long-term results of different ablation strategies according to different arrhythmic patterns

36 Paroxysmal atrial fibrillation: long-term results of different ablation strategies according to different arrhythmic patterns

36 Paroxysmal atrial fibrillation: long-term results of different ablation strategies according to different arrhythmic patterns

36 Paroxysmal atrial fibrillation: long-term results of different ablation strategies according to different arrhythmic patterns

Anesthetic management of a patient with asymptomatic ventricular tachycardia

There are many causes of ventricular arrhythmias in pediatric patients, even those with structurally normal hearts. However, in young patients with 'normal' hearts, sustained ventricular arrhythmias are relatively rare. The primary concern of the physician is to identify which patients have benign ventricular arrhythmia patterns and which are at risk for sudden cardiac death. Even in asymptomatic patients, the choice of anesthetic agents may be important to minimize precipitation of episodes of tachyarrhythmias. This clinical report describes the anesthetic considerations for an asymptomatic child with a history of sustained premature ventricular contractions, ventricular tachycardia, and bigeminy. This child had chronic serous otitis media requiring repeat tympanostomy and tube replacement. This case report outlines the initial cancellation of anesthesia because of sustained arrhythmias, and subsequent conduct of the anesthesia for the case, as well as the considerations in the selection of the drugs when a child presents with significant ventricular arrhythmia.

Different spectral components of 24 h heart rate variability are related to different modes of death in chronic heart failure

To assess whether analysis of heart rate variability (HRV) from 24 h Holter recordings provides information about the mode of death (pump failure vs. sudden death) in chronic heart failure (CHF). We analysed 24 h HRV in 330 consecutive CHF patients in sinus rhythm. Indices derived from time domain, spectral domain, and fractal analyses of 24 h automatic HRV were evaluated. Data from clinical assessment, echocardiography, right heart catheterization, exercise test, blood biochemical examination, and arrhythmia pattern were analysed. Patients were followed up for 3 years. Two simple multivariable models, both including 24 h spectral indices, were able to identify patients at higher risk of progressive pump failure and sudden death, respectively. Depressed power of night-time HRV (< or = 509 ms(2)) below 0.04 Hz [very low frequency (VLF)], high pulmonary wedge pressure (PWP > or = 18 mm Hg) and low left ventricular ejection fraction (LVEF < or = 24%) were independently related to death for progressive pump failure, while the reduction of power between 0.04 and 0.15 Hz at night (LF < or = 20 ms(2)) and increased left ventricular end-systolic diameter (LVESD > or = 61 mm) were linked to sudden mortality. Automatic spectral analysis of 24 h HRV provides independent risk indices related to mode of death in sinus rhythm CHF patients.

Phase-averaged characterization of respiratory sinus arrhythmia pattern.

A method for the accurate time-domain characterization of respiratory sinus arrhythmia (RSA) pattern is presented and applied to two groups of healthy subjects to lay the baseline of RSA patterns and to underlay their features: response to standing, stability in successive recordings, and individuality of the shape of RSA pattern. RSA pattern is evaluated by selective averaging of heart rate (HR) changes from multiple respiratory cycles over the respiratory phase and represents the complete modulating function of HR by respiration. The RSA pattern is evaluated with free respiration and even in cases of severe arrhythmia. Estimation error is 6-8% in magnitude, phase resolution is 0.2 rad, and sensitivity margin for respiratory-related HR variability (HRV) components is 1%. RSA magnitude, phase lag, and expiration-to-inspiration time ratio are derived in addition to the entire pattern. In a group of 10 healthy young adults, a phase lag difference of 11.4 +/- 8.5% (mean +/- SD, P < 0.004) was observed between supine and standing postures, possibly ascribed to breathing mechanics. A second group of 15 healthy young adults at supine rest showed stability of the RSA pattern in successive recordings (several weeks apart) as well as individuality among subjects. This may suggest a nonscalar individual long-term index for cardiorespiratory coupling. The method is complementary to the existing statistical and spectral methods. It allows the complete characterization of the primary RSA components and may provide new insight into the effects of vagal activity and changes in clinical conditions.

Histologic findings in patients with clinical and instrumental diagnosis of sporadic arrhythmogenic right ventricular dysplasia

ObjectivesWe sought to analyze the histologic findings of 30 patients with a diagnosis of arrhythmogenic right ventricular dysplasia (ARVD) based on established clinical and instrumental criteria, who did not have a family history of ARVD. BackgroundThe diagnostic role of endomyocardial biopsy (EMB) in patients with a clinical profile of ARVD is still debated. MethodsThirty patients (19 male, 11 female, mean age 27 ± 10 years) with left bundle branch block morphology ventricular tachyarrhythmias and echocardiographic, angiographic, and magnetic resonance imaging (MRI) findings diagnostic of ARVD were studied. All patients, besides diagnostic, noninvasive, and invasive cardiac studies, underwent EMB in the apex, anterior free wall, inferior wall of the right ventricle (RV) and in the septal-apical region of the left ventricle. ResultsDiagnostic histologic features of ARVD were found only in 9 (30%) patients and a myocarditis, according to the Dallas criteria, in the remaining 21 (70%) patients. Morphometric evaluation of RV samples showed significant differences in fatty tissue and myocyte percent area between ARVD and myocarditis (p < 0.001). Conversely, no difference was found between the two groups in arrhythmic patterns and structural and functional echocardiographic, angiographic, and MRI RV alterations. Magnetic resonance imaging showed hyperintense signals in 67% of ARVD and in 62% of myocarditis group (p = NS). During follow-up (mean, 23 ± 14 months), all patients with myocarditis remained stable on antiarrhythmic therapy while five patients with ARVD required implantation of an implantable cardioverter defibrillator. ConclusionsA myocarditis involving the RV can mimic ARVD. An EMB appears the most reliable diagnostic technique, with significant prognostic and therapeutic implications.

Contractile activity of cultured adult Dirofilaria immitis

A method for long-term maintenance of adult heartworms (HW) in culture for use in contractile activity studies was developed. Culture conditions included Eagle’s minimum essential medium (MEM) containing Earle’s balanced salt solution and MEM vitamins and supplemented with 10% horse serum, pH 7.6, 37 °C, and humidified 5% CO 2:95% room air atmosphere. Motility was observed for up to 91 days. Reducing the culture atmosphere from 20% oxygen to 5% oxygen reduced acid production and survival to 28 days or less. Spontaneous contractile activity of adult HW coils (1 cm diameter) was measured using an isometric force displacement transducer system. Activity had an arrhythmic pattern of good magnitude that could be recorded after up to 50 days in culture for male HW and after up to 40 days in culture for female HW. Analyses of contractile activity included determination of its amplitude, frequency, contraction index, and basal tension. Amplitude for males (3.4±1.2 g) (mean±S.D.) was significantly greater ( P<0.02) than that for females (3.0±1.1 g), whereas frequency for females (8.2±2.3 min) was significantly greater ( P<0.03) than that for males (7.5±2.3 min). The contraction index for females was 16.7±13.7 mm/min and for males, 14.4±9.0 mm/min. The difference was not significant. The contraction index was based on line integration of the record of contractile activity. Amplitude and frequency of contractile activity for anterior segments (2.5 cm), suspended lengthwise, from cultured adult female HW, were not significantly different from results for coils, but the contraction index (34.5±33.8) was significantly higher ( P<0.01) indicating that the pattern of activity was more uniform in the segments. An applied basal tension of about 4 g was suitable for the coils, while a suitable basal tension for segments was about 1.5 g. For coils, amplitude, frequency, and contraction index increased significantly ( P<0.02) with increase in basal tension. Coils were not sensitive to changes in ionic, glucose, oxygen, and osmol concentrations, and pH (6.8–7.6) of the bathing solution. A pH of 8.0 markedly increased basal tension and contractile activity. At 20 °C contractile activity stopped. These effects of pH and temperature were reversible. The HW appeared resistant to changes in their environment. This is probably related to an efficient cuticular barrier. The culture and recording methods used in this study open improved opportunities for quantitative evaluation of responsiveness of HW to a variety of physiological and pharmacological factors.