Correlation between surface and intracardiac electrocardiogram in a patient with inappropriate defibrillation shocks due to hyperkalemia

A 39-year-old man received implantable cardioverter defibrillator (ICD) shocks during sinus rhythm, triggered by an increase in amplitude and oversensing of intracardiac T waves, caused by hyperkalemia. After treatment of hyperkalemia, the T wave morphology normalized, and oversensing and inappropriate ICD shocks were eliminated. Alteration of the intracardiac electrogram was well correlated to the surface electrocardiogram (ECG) changes. Intracardiac T waves can be altered by hyperkalemia and it seems that this alteration can be estimated by surface ECG analysis.

[Tracheal resection and reconstruction for tracheal stenosis]

Five patients underwent surgery for tracheal stenosis. The cause of stenosis was congenital tracheal stenosis in 1 case, post-intubation tracheal stenosis in 1 case, and tracheal stenosis due to thyroid cancer invasion in 3 cases. All 5 patients required circumferential tracheal resection and end-to-end anastomosis using 4-0 or 5-0 absorbable sutures. The number of tracheal rings removed ranged from 3 to 6. There was no anastomotic complication. Technical points of this procedure were summarized as follows : 1) the circumferential dissection of the trachea should be made only at the level of the lesion that is to be excised, 2) preserve at least one side of recurrent nerve, 3) the traction sutures facilitate tensionless knot of the sutures, 4) prevention of excessive extension of the neck in the immediate postoperative period.

[Primary spontaneous pneumomediastinum]

We report 5 cases of spontaneous pneumomediastinum. They were 4 men and 1 female with a mean age of 17 (14-25). Four patients developed sport-related pneumomediastinum and 1 patient had a karaoke-related condition. Primary spontaneous pneumomediasinum is a rare condition. In addition, there is no previous report describing karaoke-related spontaneous pneumomediastinum. Each of the patients experienced chest pain and/or neck pain before consulting our hospital. Chest roentgenogram and chest computed tomography showed pneumomediastinum without esophageal or tracheal injury. Four patients did not require hospitalization, but 1 patient was necessary to hospitalize for 7 days because of severe chest and neck pain. None of these 5 patients has had any recurrence for more than 1 year. Differentiating this entity from other diseases involving anterior chest pain is important.

Mutational analysis of block and facilitation of HERG current by a class III anti-arrhythmic agent, nifekalant

Chemicals and toxins are useful tools to elucidate the structure-function relationship of various proteins including ion channels. The HERG channel is blocked by many compounds and this may cause life-threatening cardiac arrhythmia. Besides block, some chemicals such as the class III anti-arrhythmic agent nifekalant stimulate HERG at low potentials by shifting its activation curve towards hyperpolarizing voltages. This is called "facilitation". Here, we report mutations and simulations analyzing the association between nifekalant and channel pore residues for block and facilitation. Alanine-scanning mutagenesis was performed in the pore region of HERG. The mutations at the base of the pore helix (T623A), the selectivity filter (V625A) and the S6 helix (G648A, Y652A and F656A) abolished and S624A attenuated both block and facilitation induced by the drug. On the other hand, the mutation of other residues caused either an increase or a decrease in nifekalant-induced facilitation without affecting block. An open-state homology model of the HERG pore suggested that T623, S624, Y652 and F656 faced the central cavity, and were positioned within geometrical range for the drug to be able to interact with all of them at the same time. Of these, S649 was the only polar residue located within possible interaction distance from the drug held in its blocking position. Further mutations and flexible-docking simulations suggest that the size, but not the polarity, of the side chain at S649 is critical for drug induced facilitation.

[Thymoma transformed to thymic carcinoma with brain and bone metastases 6 years after recurrence]

We report a man who developed brain and bone metastases 6 years after resection of recurrent thymoma. The patient underwent surgery for B2-thymoma [World Health Organization (WHO) classification] without microscopic capsular invasion at 50-year-old. The next year, he underwent the second surgery for recurrent B2-thymoma as pleural dissemination. Seven months after the second surgery, he developed recurrence of pleural dissemination. The patient refused any further aggressive treatment, including surgery, chemotherapy, and radiotherapy. The pleural disease did not increase over 6 years, then suddenly enlarged. Thereafter, the patient developed left hemiparesis due to brain metastases, followed by bone metastases. Immunochemical studies of the metastatic tumors demonstrated that these lesions seemed to be poorly differentiated thymic carcinoma (small cell carcinoma) on WHO classification. We concluded that the thymoma transformed to thymic carcinoma with brain and bone metastases during 6 years.

[Sarcomatoid pleural mesothelioma presenting as posterior mediastinal tumor with dysphagia]

Case 1: A 46-year-old man with dysphagia, chest pain and cough admitted to our department. Radiological studies demonstrated a solid mass with a maximal diameter of 5cm at the posterior mediastinum. The tumor was resected, then postoperative radiotherapy (60Gy) and chemotherapy were performed. Results of histological and immunohistochemical study showed that the tumor consisted of sarcomatoid mesothelioma. The patient died of recurrence with bone metastasis 6 months after surgery. Case 2: A 76-year-old man with dysphagia, chest pain and cough admitted to our department Radiological studies demonstrated a solid mass with a maximal diameter of 12cm in the posterior mediastinum. accompanied by abundant effusion in the bilateral pleural cavities. The patient underwent open biopsy and histological and immunohistochemical study showed that the tumor consisted of sarcomatoid mesothelioma. The patient died of multiple organ failure on the 1st postoperative day. We report extremely rare cases of sarcomatoid mesothelioma that appeared to be posterior mediastinal tumor before surgery, and discuss the difficulty of diagnosing sarcomatoid mesothelioma with atypical clinical manifestations.

Intranuclear paracrystals observed in striated muscle specific LIM protein-deficient mouse cardiomyocytes

A paracrystalline structure was observed within left ventricular cardiomyocyte nuclei of MLP(-/-) mice. The paracrystal possessed cross lines, approximately 8.0 micro m long and 0.3 micro m wide, with a slender spindle shape and a periodicity of 13 nm. Paracrystals were best observed along the longitudinal orientation of myofibrils and were detected in less than 10% of the nuclei observed. One dimension of the protein unit forming the paracrystal was 8.5 nm long. The electron density of the paracrystal appeared to be slightly higher than that of heterochromatin, suggesting that RNA-associated proteins are constituents of the paracrystal. This is the first report of intranuclear paracrystals in cardiomyocytes, which appear to be unique to MLP(-/-) mice.

Decrease in amplitude of intracardiac ventricular electrogram and inappropriate therapy in patients with an implantable cardioverter defibrillator

Intracardiac electrograms are important for discrimination of tachyarrhythmia by implantable cardioverter defibrillators (ICD). A low R-wave can cause not only undersensing of ventricular tachyarrhythmia but also inappropriate discharges due to oversensing of unexpected signals because of its characteristic sensing algorithm. Therefore, this study aimed to investigate adverse events associated with R-wave amplitude. We included 115 consecutive patients followed-up over one year after implantation of a transvenous ICD system. The status of the ICD was checked every 3 months and intracardiac ventricular electrograms were analyzed. The decrease in R-wave amplitude was high in arrhythmogenic hypertrophy cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy (ARVC), and sarcoidosis. Low R-waves (< 5.0 mV) were observed in 13 patients at a follow-up of 15 +/- 16 months after implantation, and the mean R-wave was 3.0 +/- 0.8 mV. The frequency of low R-waves was high in ARVC (38%), sarcoidosis (33%), and dilated cardiomyopathy (17%). All of the dilated cardiomyopathy patients with low R-waves had severe left ventricular dysfunction. Inappropriate ICD therapy resulting from T-wave oversensing occurred in 7 patients and the R-wave was < 5.0 mV in 6 of the patients. The frequency of inappropriate therapy was high in patients with sarcoidosis. In 3 patients, inappropriate therapy caused ventricular tachyarrhythmia. In conclusion, decreases in R-wave amplitude occurred in some progressive cardiac disorders and caused inappropriate ICD discharges having arrhythmogenicity. Physicians should attempt to obtain a high R-wave amplitude during ICD implantation and careful follow-up is required, especially in patients with ARVC or sarcoidosis.

Comparison of efficacy of sotalol and nifekalant for ventricular tachyarrhythmias

BACKGROUND

Suppression of implantable defibrillator discharges associated with ventricular tachyarrhythmia (VTA) has been reported for sotalol. This study aimed to investigate the efficacy of intravenous nifekalant hydrochloride in predicting the effects of oral sotalol.

METHODS AND RESULTS

The present study included 14 patients who had sustained VTA associated with structural heart disease. All patients also had inducible VTA. To compare the effects of nifekalant and sotalol, programmed electrical stimulation was performed, in the basal state, after nifekalant administration, and after sotalol administration. Nifekalant and sotalol similarly prolonged the corrected QT interval and ventricular effective refractory periods, but the heart rate was slowed by sotalol only. In 4 of 5 patients whose VTA became non-inducible by nifekalant, subsequent treatment with sotalol also suppressed the inducible VTA. In all of the 9 patients non-responding to nifekalant, VTA remained inducible during sotalol treatment. Nifekalant accurately predicted the response to sotalol during electrophysiologic study in 13 of 14 patients. Of 11 patients who remained on sotalol, VTA recurred in 3 non-responders during a follow-up of 46 +/- 11 months.

CONCLUSIONS

Nifekalant and sotalol had similar effects on inducible VTA. The response of inducible VTA to nifekalant may predict the clinical efficacy of sotalol.

Nifekalant hydrochloride suppresses severe electrical storm in patients with malignant ventricular tachyarrhythmias

BACKGROUND

Some patients with an implantable cardioverter-defibrillator (ICD) suffer from burst of inappropriate multiple discharges (severe electrical storm), and because the current therapeutic options are limited, the effect of nifekalant hydrochloride, a new class III drug, on severe electrical storm was investigated in the present study.

METHODS AND RESULTS

Ninety-one consecutive patients treated with ICD were included in the study (M 70; mean age 58 years; left ventricular ejection fraction 45+/-15%). Severe electrical storm was defined as more than 10 ICD discharges within 1 h. During a mean follow-up period of 30+/-13 months, 41/91 (45%) patients had appropriate ICD therapy for arrhythmias and severe electrical storm occurred in 11 of them (12%) at 20+/-18 months after ICD implantation. The mean number of ICD discharges/h during severe electrical storm was 18+/-12. In 4 of 10 patients, severe electrical storm was successfully suppressed by a combination of deep sedation and beta-blocking agent; 6 other patients were refractory to this treatment, but severe electrical storm was successfully suppressed by intravenous administration of nifekalant hydrochloride with no adverse effects.

CONCLUSIONS

Nifekalant hydrochloride is an effective and safe treatment for severe electrical storm.

Elimination of late potentials by quinidine in a patient with Brugada syndrome

The beneficial effects of quinidine on ST-segment elevation, inducible ventricular tachyarrhythmias, and episodes of ventricular tachyarrhythmia have been reported in Brugada syndrome. This is the first report describing quinidine-induced elimination of the late potential, which is considered one of the parameters for an arrhythmic event, in a patient with Brugada syndrome.

[Primary lung cancer incidentally diagnosed in lung biopsy for diffuse pulmonary disease]

We here presented 2 cases of interstitial pneumonia with lung adenocarcinoma incidentally diagnosed by partially resected lung for diffuse pulmonary disease. CASE 1: A 78-year-old female was admitted to the hospital complaining of productive cough and general fatigue. The chest computed tomography (CT) revealed diffuse honey comb pattern in bilateral lung field especially in the right lower lung. Video-assisted thoracoscopic lung biopsy was performed and was diagnosed as diffuse spreading well differentiated adenocarcinoma. CASE 2: A 59-year-old male was admitted to the hospital complaining of dyspnea and general fatigue. The chest X-ray revealed right pneumothorax and chest CT revealed diffuse honey comb pattern and bullae in bilateral lung field and fibrous tumor-like lesion in the right middle lung. Video-assisted thoracoscopic lung biopsy was performed and was diagnosed as pulmonary fibrosis with papillary adenocarcinoma.

CONCLUSION

It is important to examine carefully the specimen obtained from thoracoscopic lung biopsy even if interstitial pneumonia is strongly suspected.

Mechanism of cell death in inflamed superficial digital flexor tendon in the horse

The aim of the present study was to clarify the presence and determine the role of apoptosis in the degenerative process of the superficial digital flexor tendon (SDFT) in the horse. Samples were obtained from normal and inflamed SDFTs of horses. To detect apoptosis and to identify apoptotic cells, the samples were subjected to immunohistochemical labelling and Western blot analysis. Although a large number of cells in degenerate areas showed positive reactions with caspase-3 and single stranded DNA antibodies, cells in normal tendon samples showed very weak reactions. Excessive apoptosis was confirmed by the results of Western blot analysis, which showed a significant increase in activated caspase-3 protein in the inflamed SDFTs, suggesting that apoptosis occurred in the tendinocytes via a caspase-3-dependent pathway. This is the first report of excessive apoptosis in inflamed SDFT of the horse. The results indicate that apoptosis may play an important role in the process of degeneration of the tendon as well as other tissues.

Variable Electrocardiographic Effects of Short-Term Quinidine Sulfate Administration in Brugada Syndrome

Quinidine, a class I antiarrhythmic agent with blocking property of transient outward current, is a possible candidate for the suppression of ventricular fibrillation in patients with Brugada syndrome; although there is a concern that its ability to these effects may be proarrhythmic. Therefore, we evaluated the effect of quinidine sulfate on ST-segment elevation in Brugada syndrome. In 8 patients with Brugada syndrome, the magnitude of ST-elevation at the J-point (ST(J)), and the ST-segment configuration in leads V1-V3, were compared before and on day 2 after the initiation of quinidine administration. In 3 patients, quinidine attenuated ST(J) by > or = 0.1 mV. Of these 3 patients, ST-segment elevation was normalized in 2 patients, while the ST-segment configuration was unchanged in another. In another 3 patients, quinidine augmented ST(J) by > or = 0.1 mV without any change of ST-segment configuration, and the augmentation was returned to baseline after the discontinuation of quinidine. Quinidine exhibited no effect on the ST-segment in the remaining 2 patients. The favorable effects of quinidine on the ST-segment tended to be more pronounced in patients with prominent ST-elevation at baseline. In 1 patient, quinidine was effective in eliminating both ST-segment elevation and repetitive tachyarrhythmia episodes. In conclusion, the effects of quinidine on ST-segment elevation were variable. Quinidine may potentially augment the ST-segment elevation in some patients with Brugada syndrome.

Electrophysiologic Study‐Guided Therapy with Sotalol for Life‐Threatening Ventricular Tachyarrhythmias

The aim of this study was to investigate the long-term efficacy and safety of electrophysiologic study (EPS)-guided sotalol administration combined with implantable cardioverter defibrillators (ICD) for ventricular tachyarrhythmias (VTA). This study enrolled 92 patients with both structural heart disease and sustained VTA. Sotalol was administered to 57 patients, and its efficacy was assessed by EPS. Long-term treatment was continued in combination with ICD in 31 patients (57%) whose VTA was no longer inducible (responder group) and in 16 patients whose VTA remained inducible (nonresponder group). The long-term outcomes were compared among the responder group, the nonresponder group, and 35 ICD recipients untreated with antiarrhythmic drugs (ICD-only group). During a mean follow-up of 44 +/- 33 months, the recurrence of VTA was not significantly different between all patients treated with sotalol (30%) and patients in the ICD-only group (46%). However, the recurrence of VTA was significantly lower in the responder (13%) than in the nonresponder (63%) or the ICD-only groups (46%). There was no significant difference in VTA recurrence between the nonresponder and the ICD-only groups. One patient each in the responder and the ICD-only groups died suddenly, and all-cause mortality was similar in the three groups. The incidence of inappropriate ICD discharges was less in the sotalol than in the ICD-only groups. No patient had to discontinue long-term sotalol treatment because of the adverse effects. In conclusion, sotalol reduced VTA recurrence in the responding patients and inappropriate ICD discharge. EPS may predict the efficacy of sotalol for VTA recurrence.

Unsuccessful Internal Defibrillation in Brugada Syndrome: Focus on Refractoriness and Ventricular Fibrillation Cycle Length

INTRODUCTION

In patients with Brugada syndrome, implantable cardioverter defibrillator (ICD) is the only reliable treatment to prevent sudden death though, in some cases, internal defibrillation may be unsuccessful. The aim of this study was to examine the determinants of defibrillation failure, with a focus on electrophysiologic characteristics.

METHODS

The study included 51 patients treated with ICD: 22 with Brugada syndrome and 29 with structural heart disease (SHD). The prevalence of defibrillation energy requirement precluding the programming of a 10-J safety margin, the mean right ventricular effective refractory period (ERP), and mean induced ventricular fibrillation cycle length (VFCL) from the stored ICD electrograms, were compared between the two patient groups.

RESULTS

High defibrillation requirements were observed in 18% of patients with Brugada syndrome versus 0% of patients with SHD. However, the patients with SHD had larger heart size than those with Brugada syndrome. Mean VFCL and mean ERP were both significantly shorter in patients with Brugada syndrome than in patients with SHD, and ERP and VFCL were significantly correlated.

CONCLUSION

Patients with Brugada syndrome have a high prevalence of high defibrillation energy requirement, and short ventricular ERP and VFCL.

Genomic and non-genomic regulation of L-type calcium channels in rat ventricle by thyroid hormone

Hyperthyroidism is associated with low exercise tolerance despite high cardiac output and sometimes with the development of heart failure. L-type calcium channels may play a role in the mechanism, but this has not been fully understood. We examined the effects of thyroid hormone on gene expression and function of L-type calcium channels in rat ventricles by the ribonuclease protection assay and whole-cell patch-clamp technique, respectively. The effects of bisoprolol, beta-blocking agent, on the regulation of calcium channel by thyroid hormone was also studied. In hyperthyroid animals, the mRNA of the calcium channel alpha1c subunit was reduced on day 4, compared with that in euthyroid animals, and remained low on day 8. Bisoprolol did not affect the thyroid hormone mediated decrease in alpha1c subunit mRNA. While L-type calcium current was greater in hyperthyroid than euthyroid myocytes on day 4, it was smaller on day 8. In addition, the isoproterenol-induced increase in calcium current in euthyroid rats was attenuated in hyperthyroid rats. Acetylcholine decreased calcium current in hyperthyroid myocytes, but not in euthyroid myocytes. In conclusion, L-type calcium current was increased by thyroid hormone in rat ventricular myocytes by the activation of the adenylate cyclase cascade, despite a decreased calcium channel gene expression. These genomic and non-genomic modifications may play an important role in the association of high cardiac output with low exercise tolerance, and in the development of heart failure in hyperthyroidism.

Phosphatidylinositol 3,4,5-trisphosphate and Ca2+/calmodulin competitively bind to the regulators of G-protein-signalling (RGS) domain of RGS4 and reciprocally regulate its action

RGS (regulators of G-protein signalling) are a diverse group of proteins, which accelerate intrinsic GTP hydrolysis on heterotrimeric G-protein a subunits. They are involved in the control of a physiological behaviour known as 'relaxation' of G-protein-gated K+ channels in cardiac myocytes. The GTPase-accelerating activity of cardiac RGS proteins, such as RGS4, is inhibited by PtdIns(3,4,5)P3 (phosphatidylinositol 3,4,5-trisphosphate) and this inhibition is cancelled by Ca2+/calmodulin (CaM) formed during membrane depolarization. G-protein-gated K+ channel activity decreases on depolarization owing to the facilitation of GTPase-activating protein activity by RGS proteins and vice versa on hyperpolarization. The molecular mechanism responsible for this reciprocal control of RGS action by PtdIns(3,4,5)P3 and Ca2+/CaM, however, has not been fully elucidated. Using lipid-protein co-sedimentation assay and surface plasmon resonance measurements, we show in the present study that the control of the GTPase-accelerating activity of the RGS4 protein is achieved through the competitive binding of PtdIns(3,4,5)P3 and Ca2+/CaM within its RGS domain. Competitive binding occurs exclusively within the RGS domain and involves a cluster of positively charged residues located on the surface opposite to the Ga interaction site. In the RGS proteins conserving these residues, the reciprocal regulation by PtdIns(3,4,5)P3 and Ca2+/CaM may be important for their physiological regulation of G-protein signalling.

Postprandial Variations in ST-Segment in a Patient with Brugada Syndrome and Partial Gastrectomy

A 74-year-old man with a history of partial gastrectomy presented with an electrocardiogram consistent with Brugada syndrome and marked meal related fluctuations in the ST segment. ST-segment elevation was prominently attenuated at 30 minutes and increased at 120 minutes after meals. Analysis of heart rate variability revealed a relationship between postprandial heightened parasympathetic activity and increase in Brugada-type ECG abnormality. A rapid postprandial increase in blood glucose may initially stimulate sympathetic nervous activity and secondarily increase parasympathetic tone. Food intake can be associated with fluctuations in ST-segment elevation in patients with the Brugada syndrome.

Historical view of schistosomiasis japonica in Japan: implementation and evaluation of disease-control strategies in Yamanashi Prefecture

We summarized historical aspects of disease control activities targeting schistosomiasis japonica in Kofu basin, Yamanashi Prefecture, Japan. Kofu Basin was one of the biggest endemic foci of schistosomiasis japonica in Japan, and the last place where transmission of Schistosoma japonicum was confirmed in Japan. Because of the most severe endemic situations in Yamanashi, intensive control measures had been implemented by the central as well as the local government. The last human case in Japan was in 1977, which is just before praziquantel being available. Therefore, the main efforts were focused on snail control. Mass examination and mass chemotherapy were implemented, however, the compliance was not so good because of the severe side effects due to the available therapeutics, Stibnal. Along with socioeconomic development after World War II, big changes in land use, life style, and farming led drastic reduction in the disease prevalence in Kofu Basin in the 1960s. A large amount of budget was also used for disease control. Cementing water canals covered more than 95% of paddy fields in Kofu Basin, and this resulted in ecological changes. After elimination of schistosomiasis, environmental repair is the urgent subject in Kofu Basin. Our experiences in Yamanashi contain both good influences and also a lot of reflection. It is important to evaluate each activity in our history before we give intensive cooperation with countries where endemic foci is still present.

Thyroid hormone regulates mRNA expression and currents of ion channels in rat atrium

Atrial fibrillation is one of the common arrhythmias associated with hyperthyroidism. This study examined the effects of thyroid hormone (T3) on mRNA expression and currents of major ionic channels determining the action potential duration (APD) in the rat atrium using the RNase protection assay and the whole-cell patch-clamp technique, respectively. T3 increased the Kv1.5 mRNA expression and decreased the L-type calcium channel mRNA expression, while the Kv4.2 mRNA expression did not change. APD was shorter in hyperthyroid than in euthyroid myocytes. The ultrarapid delayed rectifier potassium currents were remarkably increased in hyperthyroid than in euthyroid myocytes, whereas the transient outward potassium currents were unchanged. L-type calcium currents were decreased in hyperthyroid than in euthyroid myocytes. T3 shifted the current-voltage relationship for calcium currents negatively. In conclusion, T3 increased the outward currents and decreased the inward currents. The resultant changes of ionic currents shortened APD, providing a substrate for atrial fibrillation.

Function, subcellular localization and assembly of a novel mutation of KCNJ2 in Andersen's syndrome

Andersen's syndrome (AS) (which is characterized by periodic paralysis, cardiac arrhythmias and dysmorphic features), a hereditary disease, and missense mutations of KCNJ2 (which encodes an inward rectifying potassium channel) have been reported recently. We performed clinical and molecular analyses of a patient with AS, and found a novel mutation (G215D) of KCNJ2. Twelve-lead electrocardiography revealed a long QT interval and frequent premature ventricular contractions, and polymorphic ventricular tachycardia was induced by programmed electrical stimulation. Use of a conventional whole-cell patch-clamp system with COS7 cells demonstrated that the G215D mutant was non-functional, and that co-expression of wild type (WT)- and mutant-KCNJ2 shows a dominant negative effect on both inward and outward currents. We performed confocal laser scanning microscopy to assess the cellular trafficking of WT- and mutant-KCNJ2 subunits tagged with yellow fluorescent protein (YFP) and cyan fluorescent protein (CFP), respectively. Tagging with the YFP did not affect the channel function of WT-KCNJ2 and both proteins showed similar plasma membrane fluorescence patterns. Furthermore, the result of fluorescence resonance energy transfer (FRET) studies at the plasma membrane region suggested that both YFP-tagged WT- and CFP-tagged mutant-KCNJ2 combine to construct a hetero-multimer of the potassium channel. In conclusion, the G215D mutant of KCNJ2 is distributed normally in the plasma membrane, but exhibits a dominant-negative effect and reduces the Kir2.1 current, presumably due to hetero-multimer construction.

Ventricular tachyarrhythmias in a canine model of LQT3: arrhythmogenic effects of sympathetic activity and therapeutic effects of mexiletine

The ventricular tachyarrhythmias associated with the LQT3 syndrome are typically bradycardia-dependent. However, some episodes can be associated with exercise or emotional stress, suggesting a different arrhythmogenic mechanism when sympathetic activity predominates. This study examined the potential arrhythmogenic mechanisms during periods of autonomically mediated transient heart rate acceleration in a canine anthopleurin-A model of LQT3 syndrome. Using plunge needle electrodes, transmural unipolar electrograms of the left ventricle were recorded from endocardial (Endo), mid-myocardial (Mid) and epicardial (Epi) sites. The activation-recovery interval (ARI) was measured to estimate local refractoriness. The cardiac cycle length was gradually shortened by cessation of vagal stimulation (vagal stimulation protocol (VSP)), and intramural electrograms and onset mode of ventricular tachyarrhythmias were analyzed in 7 experiments. The VSP was performed 8 times before and 5 times after administration of mexiletine in each experiment. Before mexiletine, vagal stimulation slowed the heart rate and created large transmural ARI dispersion because of a greater ARI prolongation at Mid rather than Epi/Endo sites. After cessation of vagal stimulation, unipolar electrograms started to show ARI alternans and ventricular premature beats developed sporadically. Sustained ventricular tachyarrhythmias were induced in 12 of the 56 trials of the VSP. Initiation of ventricular tachyarrhythmias was associated with delayed conduction at Mid/Endo sites. Mexiletine attenuated transmural ARI dispersion, and neither ARI alternans nor ventricular tachyarrhythmias was observed during all 35 trials of the VSP after mexiletine administration. Heart rate acceleration induced by an abrupt shift to a state of predominant sympathetic activity enhances arrhythmias in this LQT3 model. Mexiletine homogenizes ventricular repolarization, suppresses premature complexes and was antiarrhythmic during ventricular tachyarrhythmias induced by the VSP.

Suppression of electrical storm by biventricular pacing in a patient with idiopathic dilated cardiomyopathy and ventricular tachycardia

This study presents a patient with idiopathic dilated cardiomyopathy who had suffered from multiple ICD shocks. Amiodarone and a beta-blocker failed to suppress ventricular tachycardia. His ECG showed a very wide QRS complex with an intraventricular conduction delay, so biventricular (BV) pacing was attempted. The BV pacing successfully prevented the multiple ICD shocks accompanied with an improvement in left ventricular systolic function and physical activity.

Different gene expression of potassium channels by thyroid hormone and an antithyroid drug between the atrium and ventricle of rats

Thyroid hormone has been shown to modulate the gene expression of cardiac potassium channels, however, it is not known if gene expression is different between the atrium and the ventricle. The long-term effects of thyroid hormone on nuclear thyroid hormone receptors are also not known. Triiodothyronine (T3) at 25 microg/100 g of body weight or propylthiouracil (PTU) at 4 mg/100 g of body weight was given to adult rats via a gastric tube for 14 days. The levels of mRNA of Kv1.2. Kv1.4, Kv1.5, Kv2.1, Kv4.2, erg, LQT1, and minK were assayed by RNase protection assay. The mRNA of nuclear T3-receptor-al and T3-receptor-beta1 were also assayed for 15 days. After T3 (or PTU), plasma free T3 and free T4 increased (or decreased) significantly. The mRNA levels of Kv1.2 and Kv1.4 were reduced after T3 in the atrium and the ventricle. while PTU increased the levels in both chambers. Kv1.5 was significantly up-regulated by T3 in the atrium and the ventricle (P < 0.02 for both) and PTU decreased its expression in the ventricle (P < 0.02). Kv2.1 and Kv4.2 were not affected by T3 or PTU. mRNA of erg was not affected by T3 in the atrium but decreased in the ventricle (P < 0.01). After PTU, erg mRNA was decreased in the atrium (P < 0.02) but increased in the ventricle (P < 0.01). LQT1 was decreased by T3 in both chambers (P < 0.01) and not affected by PTU. minK was not detectable in the control state and was up-regulated only in the atrium: a peak on the 4th day followed by a decline to the undetectable level on the 10-15th days. During T3 treatment, nuclear T3-receptor-alpha1 and beta1 mRNA were decreased in the initial 3 days but returned to control levels thereafter.

CONCLUSIONS

Between the atrium and ventricle of the adult rat heart, the responses of gene expression of voltage-gated potassium channels to T3 or PTU were quantitatively or qualitatively different and the differential responses may explain cardiac manifestations of hyperthyroidism, which is a frequent complication of supraventricular arrhythmia.

Alpha1-syntrophin-deficient skeletal muscle exhibits hypertrophy and aberrant formation of neuromuscular junctions during regeneration

Alpha1-syntrophin is a member of the family of dystrophin-associated proteins; it has been shown to recruit neuronal nitric oxide synthase and the water channel aquaporin-4 to the sarcolemma by its PSD-95/SAP-90, Discs-large, ZO-1 homologous domain. To examine the role of alpha1-syntrophin in muscle regeneration, we injected cardiotoxin into the tibialis anterior muscles of alpha1-syntrophin-null (alpha1syn-/-) mice. After the treatment, alpha1syn-/- muscles displayed remarkable hypertrophy and extensive fiber splitting compared with wild-type regenerating muscles, although the untreated muscles of the mutant mice showed no gross histological change. In the hypertrophied muscles of the mutant mice, the level of insulin-like growth factor-1 transcripts was highly elevated. Interestingly, in an early stage of the regeneration process, alpha1syn-/- mice showed remarkably deranged neuromuscular junctions (NMJs), accompanied by impaired ability to exercise. The contractile forces were reduced in alpha1syn-/- regenerating muscles. Our results suggest that the lack of alpha1-syntrophin might be responsible in part for the muscle hypertrophy, abnormal synapse formation at NMJs, and reduced force generation during regeneration of dystrophin-deficient muscle, all of which are typically observed in the early stages of Duchenne muscular dystrophy patients.

Triggers of ventricular tachyarrhythmias and therapeutic effects of nicorandil in canine models of LQT2 and LQT3 syndromes

OBJECTIVES

We sought to identify the triggers of ventricular tachyarrhythmia (VTA) in experimental models of long QT type 2 (LQT2) and long QT type 3 (LQT3) syndromes.

BACKGROUND

Most adverse cardiac events occurring in the long QT type 1 syndrome are related to sympathetic nerve activity. In contrast, various factors may trigger VTA in patients with LQT2 and LQT3.

METHODS

The mode of onset of VTA and therapeutic effects of the potassium-adenosine triphosphate channel opener nicorandil were compared in canine models of LQT2 and LQT3, using three induction protocols: 1) bradycardia produced by atrioventricular block (BRADY); 2) programmed ventricular stimulation; and 3) electrical stimulation of the left stellate ganglion (left stellate stimulation [LSS]). Transmural unipolar electrograms were recorded, and the activation-recovery interval (ARI) was measured.

RESULTS

Ventricular tachyarrhythmias developed during BRADY in all six experiments in the LQT3 model, but in none of the six experiments in LQT2. Programmed ventricular stimulation induced VTA in two experiments of the LQT2 model, but in none of the LQT3 experiments. Stimulation of the left stellate ganglion induced VTA in three experiments in LQT2 and in two experiments in LQT3. Nicorandil caused greater shortening of ARI and greater attenuation of transmural ARI dispersion in the LQT2 model than in the LQT3 model. After treatment with nicorandil, a single VTA was induced in the LQT2 model by LSS, whereas in the LQT3 model, VTA remained inducible by BRADY in four experiments and LSS in one experiment.

CONCLUSIONS

An abrupt increase in sympathetic activity appeared arrhythmogenic in both models. Nicorandil attenuated the heterogeneity of ventricular repolarization and suppressed the induction of VTA in the LQT2 model, but had a limited therapeutic effect in the LQT3 model.

Arrhythmogenesis of T wave alternans associated with surface QRS complex alternans and the role of ventricular prematurity: observations from a canine model of LQT3 syndrome

INTRODUCTION

T wave alternans (TWA) is characterized by cycle-to-cycle changes in the QT interval and/or T wave morphology. It is believed to amplify the underlying dispersion of ventricular repolarization. The aim of this study was to examine the mechanisms and arrhythmogenesis of TWA accompanied by QRS complex and/or blood pressure (BP) waveform alternans, using transmural ventricular electrogram recordings in an anthopleurin-A model of long QT syndrome.

METHODS AND RESULTS

The cardiac cycle length was gradually shortened by interruption of vagal stimulation, and TWA was induced in six canine hearts. Transmural unipolar electrograms were recorded with plunge needle electrodes from endocardial (Endo), mid-myocardial (Mid), and epicardial (Epi) sites, along with the surface ECG and BP. The activation-recovery interval (ARI) was measured to estimate local refractoriness. During TWA, ARI alternans was greater at the Mid than the Epi/Endo sites, and it was associated with the development of marked spatial dispersion of ventricular repolarization. As TWA increased, ventricular activation of the cycles associated with shorter QT intervals displayed delayed conduction at the Mid sites as a result of a critically longer ARI of the preceding cycle and longer QT interval, while normal conduction was preserved at the Epi site. Delayed conduction at the Mid sites manifested as surface ECG QRS and BP waveform alternans, and spontaneous ventricular tachyarrhythmias developed in absence of ventricular prematurity. In other instances, in absence of delayed conduction during TWA, ventricular premature complexes infringed on a prominent spatial dispersion of ventricular repolarization of cycles with long QT intervals and initiated ventricular tachyarrhythmia.

CONCLUSION

TWA accompanied by QRS alternans may signal a greater ventricular electrical instability, since it is associated with intramural delayed conduction, which can initiate ventricular tachyarrhythmia without ventricular premature complexes.

Limited role of coronary angioplasty and stenting in coronary spastic angina with organic stenosis

OBJECTIVES

We investigated the efficacy of percutaneous coronary intervention (PCI) in patients with coronary spastic angina (CSA) and severe organic stenosis.

BACKGROUND

Coronary spasm occurs at the site of organic stenosis in most patients with CSA and severe stenosis, whereas multivessel spasm occurs frequently in those with normal coronary arteries. The incidence of multivessel spasm and the efficacy of PCI in patients with CSA and severe stenosis have not been fully elucidated.

METHODS

Forty-five patients with CSA and severe stenosis underwent spasm provocative testing with intracoronary acetylcholine before and 7 +/- 3 months after PCI (20 patients had angioplasty and 25 patients had stenting), when all patients were free of restenosis.

RESULTS

Spasm was induced at the site of severe stenosis in 30 patients (66.7%) with (n = 12) or without (n = 18) spasm induced in another vessel. In the remaining 15 patients, spasm was induced at a different site in the stenotic vessel and/or in another vessel. Repeat provocative tests were performed in 43 of 45 patients. Although spasm was never induced at exactly the same site of the initial stenosis that had been dilated, spasm was induced at a different site in the dilated vessel and/or in another vessel, in 33 (76.7%) of 43 patients. Multivessel spasm occurred in 28 (62.2%) of 45 patients on one or both provocations.

CONCLUSIONS

Spasm was frequently induced at a site different from the initial stenosis, even in the absence of restenosis after PCI. Calcium antagonists should be continued in most patients with CSA who show no restenosis after PCI.

Inhibitory effect of M50054, a novel inhibitor of apoptosis, on anti-Fas-antibody-induced hepatitis and chemotherapy-induced alopecia

M50054, 2,2'-methylenebis (1,3-cyclohexanedione), was identified as a novel inhibitor of apoptosis (programmed cell death) using an in vitro cell death assay system induced in human Fas-expressing WC8 cells by soluble human Fas ligand. Furthermore, M50054 inhibited the apoptotic cell death of U937, a human monocytic leukemic cell line, induced by anticancer agents such as etoposide; it was also confirmed that M50054 inhibited apoptotic features such as DNA fragmentation and phosphatidylserine exposure in these cells. These anti-apoptotic effects were attributable to inhibition of caspase-3 activation. Additionally, M50054 significantly inhibited anti-Fas-antibody-induced elevation of plasma alanine aminotransferase and aspartate aminotransferase. Alopecia (hair loss) symptoms were also significantly improved with topical treatment with M50054. In conclusion, M50054 inhibits apoptosis induced by a variety of stimuli via inhibition of caspase-3 activation, and may thus be effective for hepatitis and chemotherapy-induced alopecia.

Inappropriate discharges by fourth generation implantable cardioverter defibrillators in patients with ventricular arrhythmias

The study prospectively investigated the incidence, cause and efficient management of inappropriate discharge by the fourth generation implantable cardioverter-defibrillator (ICD) system in 45 patients (mean age, 57+/-16 years). During the follow-up period of 27+/-17 months, 18 patients (40%) experienced one or more inappropriate therapies: sinus and supraventricular tachycardia (15 patients) and T wave oversensing (3 patients). In the 15 patients, re-programming of the tachycardia detection interval and/or additional treatment with beta-blocking agents were effective. In the 3 patients with T wave oversensing, the arrythmia was associated with an increase in T wave amplitude, change in T wave morphology and decreased R wave amplitude, and re-programming of the sensitivity of the local electrogram or changing the number of intervals to detect ventricular tachycardia decreased the number of inappropriate discharges in all 3 patients. In conclusion, inappropriate therapies are common problems in patients treated with the fourth generation ICD system, but most of them can be resolved using the dual-chamber ICD system. However, in patients with T-wave oversensing, it is difficult to avoid inappropriate discharge completely, even if the dual-chamber ICD system is implanted.

Effect of trapidil on effector functions of monocytes related to atherosclerotic plaque

The infiltration and activation of inflammatory cells play an important role in the formation and stability of coronary atherosclerotic plaque in patients with acute coronary syndrome. In this study, we evaluated the effect of trapidil, an anti-platelet agent, on atheroma-related functions of human T cells and monocytes. Trapidil and anti-CD154 (CD40 ligand) antibody inhibited the increase of procoagulant activity in the mixed lymphocyte reaction; trapidil also suppressed the induction of tissue factor, monocyte chemoattractant protein-1 (MCP-1) and matrix metalloproteinase-9 in the mixed lymphocyte reaction. Trapidil did not alter CD154 expression on isolated T cells, but it diminished CD40 expression on isolated monocytes and human monocytic leukemia THP-1 cells stimulated with interferon-gamma. Moreover, trapidil reduced MCP-1 production of isolated monocytes and THP-1 cells stimulated with interferon-gamma plus CD154-transfected cells. This effect was not seen with other tested anti-platelet agents and coronary vasodilators. In conclusion, trapidil directly acts on monocytes/macrophages to lower their susceptibility to CD154 on T cells.

Location and length of arteriovenous fistulas around axial-pattern skin-flap pedicles

The importance of the location of a surgically-created arteriovenous fistula around the pedicle (both distal and proximal) on the viability of rat skin flaps was investigated. The animals were randomly divided into four groups. Group 1 included bilateral standard island groin flaps. The right side flap was used as a control. On the left side, after elevation of the flap, an X-type arteriovenous fistula greater than 1 mm (up to 2 mm) in length was created distal to the pedicle, and just before the bifurcation of the common femoral vessels. In Group 2, the flap was an axial-pattern medially-based peninsular flap, including the same vessels. In this group also, two flaps were elevated bilaterally, and the right side was used as a control; on the left side, an X-type arteriovenous fistula the same length as in Group 1 was also created distal to the pedicle. In both groups, all other branches of the common femoral vessels were kept intact. In a second part of the study, two other animal groups were used to clarify the importance of the length of the arteriovenous fistula on the viability of skin flaps. In Group 3, the model was the same as in Group 1, but the fistula was 1 mm in length. In Group 4, the length of the fistula was 1 mm, and its location was on the common femoral vessels proximal to the pedicle, using the same flap model. Flow values were measured repeatedly using a laser Doppler flowmeter. Histopathologic studies were also done. There are three important points arising from these studies. 1). The location of an X-type arteriovenous fistula around an island skin flap pedicle seems to be more important than diameter. An arteriovenous fistula proximal to the pedicle is more hazardous than an arteriovenous fistula distal to the pedicle, regarding island skin-flap viability. 2). However, the length of the fistula is also important, and an arteriovenous fistula distal to the pedicle, with a sufficiently long length, is not devoid of harmful effects. It is also clear that the larger the fistula, the greater the systemic effects. 3). An island skin flap with an arteriovenous fistula distal to its pedicle might be a useful model to study the relationship between skin-flap viability and edema formation.

Synthesis and evaluation of 1-arylsulfonyl-3-piperazinone derivatives as factor Xa inhibitor

Intravascular clot formation is an important factor in a number of cardiovascular diseases. Therefore, the prevention of blood coagulation has become a major target for new therapeutic agents. One attractive approach is the inhibition of factor Xa (FXa), which is a key enzyme in coagulation cascade responsible for the generation of thrombin by limited proteolysis of its zymogen, prothrombin. We have investigated 1-arylsulfonyl-3-piperazinone derivatives, containing a 4-(piperidino)pyridine group in place of guanidino and/or amidino groups, and discovered compound M55113 (30a: 4-[(6-Chloro-2-naphthalenyl)sulfonyl]-1-[[1-(4-pyridinyl)-4-piperidinyl]methyl]piperazinone), as a potent inhibitor of FXa (IC50=0.06 microM) with high selectivity for FXa over trypsin and thrombin.

Differences in cell kinetic changes among renal cancer cell lines treated with interferon-alpha

BACKGROUND

Interferon (IFN)-alpha shows certain clinical effects on the treatment of renal cell carcinoma. The purpose of the present study was to investigate its direct effects and to compare the responses among different human renal cancer cell lines.

METHODS

Three cell lines, ACHN, RCC10RGB and OS-RC-2, were incubated with IFN-alpha and evaluated using MTT assay for cell proliferation and two-color flow cytometry for cell-cycle-specific cyclin expressions coupled with DNA ploidy analysis.

RESULTS

Interferon-alpha inhibited cell proliferation and caused cell accumulation at S and G2/M phases. However, IFN-alpha induced no significant change in cyclins D1, E, A or B1 expression. Interestingly, cell kinetic changes caused by IFN-alpha were different among cell lines. Cell proliferation was suppressed most in ACHN, then RCC10RGB and least in OS-RC-2. Comparing DNA histograms, ACHN showed distinct increase of G2/M cells associated with elevation of late S cells. RCC10RGB showed a predominant increase of whole S cells accompanied with a slight increase of G2/M. OS-RC-2 showed a modest increase of S cells with a little change of G2/M cells. Chronological observation revealed that S-phase increase and proliferative inhibition appeared on day 1 and day 3, respectively, in ACHN and RCC10RGB, and on day 5 in OS-RC-2.

CONCLUSIONS

Interferon-alpha induced substantial cell kinetic interference directly in the tested human renal carcinoma cell lines. The degree of change was different according to the nature of the cell line. It may partly indicate the variety of the efficacy of IFN-alpha treatment against renal cancers.

Inappropriate discharges from an intravenous implantable cardioverter defibrillator due to T-wave oversensing

This report describes the clinical management of 2 patients with ventricular fibrillation (VF) who received inappropriate shocks from an implantable cardioverter defibrillator (ICD) due to T-wave oversensing. Cardiac sarcoidosis was confirmed as the underlying heart disease in 1 patient and idiopathic dilated cardiomyopathy in the other. Within 2 months after ICD implantation, both patients received several inappropriate shocks during sinus rhythm. Stored electrograms showed decreased R-wave amplitudes and increased T-wave amplitudes. The ICD sensed both R- and T-waves as ventricular activation, which met the rate criteria for VF treatment. Reprogramming the sensing threshold in association with administration of a drug to slow the heart rate decreased the incidence of the inappropriate shocks in both patients, but these palliative measures did not completely suppress the inappropriate shocks. To avoid T-wave oversensing, the repositioning or adding of a sensing lead is required. The potential risk of T-wave oversensing in ICD patients who have small R-wave amplitudes should be recognized.

Nerve conduit using fascia-wrapped fibrocollagenous tube

The purpose of this study was to evaluate the application of autogenous fascia as a framework of a fibrocollagen tube for a nerve conduit in Japanese white rabbits. The fascia was wrapped with a double layer around a silicone rod 3.0 mm in diameter. After the implantation of the fascia-wrapped silicone rod into a subcutaneous pocket for 2 weeks, a 3.0 x 30-mm fascia-wrapped fibrocollagen (FFC) tube was prepared. With microvascular techniques, the tube was interposed into a right sciatic nerve gap which was 25 mm long. The results of nerve regeneration in the FFC tube group, in particular, the formation of epineurium, were able to stand comparison with the results of a control group under both histologic and electron micrographic examination.

Noninvasive detection and prediction of bladder cancer by fluorescence in situ hybridization analysis of exfoliated urothelial cells in voided urine

OBJECTIVES

To investigate the clinical utility of fluorescence in situ hybridization (FISH) of voided urine in the detection of bladder cancer and the prediction of its recurrence.

METHODS

FISH with centromere-specific probes for chromosomes 9 and 17 was performed to evaluate the chromosomal alterations of exfoliated urothelial cells in voided urine obtained from 44 patients with bladder cancer and 20 controls. The analysis was also performed in 17 patients with bladder cancer after complete transurethral resection to prospectively determine whether FISH can predict tumor recurrence.

RESULTS

The sensitivity to detect bladder cancer by FISH analysis (85%) was significantly higher than that by urine cytologic examination (32%) and by the bladder tumor antigen test (64%) (P <0.0001 and P = 0.026, respectively). The specificity of FISH, cytologic analysis, and the bladder tumor antigen test was 95%, 100%, and 80%, respectively. Among the 17 patients tested after transurethral resection, 7 of 13 FISH-positive patients developed tumor recurrence within the 27-month follow-up period; none of 4 FISH-negative patients developed recurrence during the same period. The recurrence rate in patients with the loss of chromosome 17 was 100%, significantly higher than the 23% for patients without this alteration (P = 0.015).

CONCLUSIONS

These findings suggest that FISH analysis of exfoliated urothelial cells in voided urine can efficiently detect bladder cancer and predict its recurrence.

[Present situation of drug resistance and future prospects]

Antibiotic resistance has evolved over 60 years from a merely microbiological curiosity to a serious medical problem in hospitals. Resistance has been reported in almost all species of bacteria to various classes of antimicrobial agents including recently evaluated ones. Bacteria regulated resistance by different mechanisms. Inappropriate use of an antimicrobial agent selects resistant strains much more frequently. Since it is not expected that some epoch-making new antimicrobial agents will be developed in the near future, proper use of existing antimicrobial agents which is based on the mechanisms of action of antimicrobial agents and of resistance of bacteria, and of control of nosocomial infection are very important to reduce the further spread of resistant bacteria. With the search for natural sources of new antimicrobial substances now appearing frustrated, the genomic approach in the 21st century may be the only fruitful way to develop truly novel chemotherapeutic agents against bacterial diseases.

Significance of end-tidal P(CO(2)) response to exercise and its relation to functional capacity in patients with chronic heart failure

OBJECTIVES

The value of end-tidal PCO(2) monitoring during exercise in patients with chronic heart failure has not been elucidated. The present study was designed to examine end-tidal PCO(2) response to exercise and its relation to functional capacity in patients with chronic heart failure.

METHODS AND RESULTS

Maximal upright ergometer exercise with respiratory gas analysis and arterial blood gas analysis were performed in 105 patients with chronic heart failure (34 patients in New York Heart Association [NYHA] class I, 38 patients in NYHA class II, and 33 patients in NYHA class III) and 14 normal control subjects. Peak O(2) uptake, excessive exercise ventilation as assessed by the slope of the relation between expired minute ventilation and CO(2) output (VE-VCO(2)), and the ratio of physiologic dead space to tidal volume (VD/VT) were determined. Cardiac output was also measured during exercise in 28 patients with chronic heart failure. Arterial PO(2) or PCO(2) values at rest and during exercise were not different among the four groups. However, end-tidal PCO(2) was significantly lower, and arterial to end-tidal PCO(2) difference and VD/VT were significantly higher in NYHA class III patients than other groups during exercise. The maximal end-tidal PCO(2) during exercise was significantly reduced as the severity of chronic heart failure advanced (45.7 +/- 4.0 mm Hg in normal control subjects, 43.5 +/- 4.8 mm Hg in NYHA class I patients, 39.7 +/- 5.1 mm Hg in NYHA class II patients, and 34.9 +/- 5.3 mm Hg in NYHA class III patients). The maximal end-tidal PCO(2) during exercise was significantly correlated with peak O(2) uptake (r = 0.68; p < 0.001) and maximal cardiac index (r = 0.73; p < 0.001), and inversely related to Ve-VCO(2) (r = - 0.84; p < 0.001) and VD/VT at peak exercise (r = -0.65; p < 0.001).

CONCLUSIONS

The decreased end-tidal PCO(2) during exercise, which is caused by high ventilation/perfusion ratio mismatching, reflects both reduced cardiac output response to exercise and increased exercise ventilation due to enlarged physiologic dead space in advanced chronic heart failure. The end-tidal PCO(2) during exercise can be used to evaluate the functional capacity of patients with chronic heart failure.