José Rubín

Increases in ornithine decarboxylase activity in the positive inotropism induced by androgens in isolated left atrium of the rat

It is well established that the intracellular receptors of androgens act as transcription factors upon their activation by androgen binding. However, a growing number of studies have associated androgens with rapid biological responses independent of their classical action mechanism. In this sense, 5alpha- and 5beta-dihydrotestosterone elicited a rapid positive inotropism in the isolated left atrium of the rat via cAMP-dependent mechanisms that may involve genomic effects. In addition, polyamines are mediators of several biological actions including those acute and long-term effects induced by androgens in the heart. The present study analyzed the role of polyamine synthesis in the cardiotonic effect of androgens in the left atrium of male Wistar rats, electrically stimulated (0.5 Hz, 5 ms and supramaximal voltage) and placed in an organ bath in 10 ml of Tyrodes solution. Incubation in the organ bath with an inhibitor of ornithine decarboxylase activity, alpha-difluoromethylornithine 10 mM, significantly decreased the positive inotropism induced by 5alpha- and 5beta-dihydrotestosterone (0.1-100 microM). This suggests that ornithine decarboxylase seems to be involved in androgen-induced positive inotropism. Furthermore, 6-min exposure to 5alpha- or 5beta-dihydrotestosterone significantly increased the activity of ornithine decarboxylase from 61.81+/-7.53 (control) to 93.28+/-9.45 and 80.28+/-12 pmol/h/mg of protein, respectively. Northern blot analysis showed that 5alpha- and 5beta-dihydrotestosterone did not modify the level of expression of the ornithine decarboxylase gene. Therefore, our results suggest that polyamine synthesis might be involved in the positive inotropism elicited by androgens through the stimulation of ornithine decarboxylase activity without changes in the expression of the ornithine decarboxylase gene.

Intracellular cAMP increases during the positive inotropism induced by androgens in isolated left atrium of rat

Molecular interactions of androgens with the plasma membrane may produce rapid cardiovascular effects that cannot be explained by the classic genomic mechanisms. In this sense, 5 alpha- and 5 beta-dihydrotestosterone-induced an acute positive inotropic effect in isolated left atrium of rat, an effect which may be due to cAMP-dependent mechanisms. To prove this, intracellular levels of cAMP, after exposure to androgens in the organ bath, and binding to beta(1)-adrenoceptors were evaluated. After a 4-min exposure, 5 alpha- and 5 beta-dihydrotestosterone increased cAMP levels from 3.83+/-0.61 to 6.15+/-1.1 and 11.18+/-2.4 pmol cAMP/mg of protein, respectively. These increases were inhibited by atenolol and not modified by treatment of the rats with reserpine. The androgen-induced cAMP increase seems to be produced via an extracellular interaction, because positive inotropism and raised levels of cAMP were produced by 5 alpha-dihydrotestosterone conjugated with bovine serum albumin (BSA). In addition, it is independent of beta(1)-adrenoceptor activation, because neither androgen displaced [(3)H]dihydroalprenolol binding. Therefore, the androgens induced a positive inotropic effect via a postsynaptic effect that increases intracellular levels of cAMP. This effect is modulated by transcriptional mechanisms or by a protein with a short half-life.

Role of putrescine on androgen-elicited positive inotropism in the left atrium of rats.

Functional and biochemical studies were performed in isolated left atria of male Wistar rats to study whether endogenous polyamines may mediate androgen-elicited positive inotropism and their relationship with a rise in cAMP during the cardiotonic effect. 5α-Dihydrotestosterone (100 μM) exposure increased intracellular putrescine as determined by HPLC, but it did not increase spermidine and spermine. This effect was antagonized by an inhibitor of ornithine decarboxylase, α-difluoromethylornithine (10 mM), suggesting enzyme activation. α-Difluoromethylornithine also antagonized androgens-elicited inotropism and the increase in intracellular cAMP. Putrescine (1 to 10 mM) elicited a concentration-dependent positive inotropism associated with the cAMP increase. The prior incubation with putrescine antagonized 5α-dihydrotestosterone-elicited inotropism and did not produce sinergism on intracellular cAMP. Short-term incubation with 5α-dihydrotestosterone or forskolin shifted to the left the cardiotonic effect of isoproterenol, an agonist of β-adrenoceptors, without any increase in Emax, suggesting that a common mechanism was involved. Therefore, polyamines might modulate the cAMP production associated with the cardiotonic effect of androgens.

Unusual case of coronary stenosis caused by an external compression

Endocarditis is a pathology with a high rate of a large abscess that extended from the aortic valve complications, some peripheral, such as the embolizaring to the pulmonary artery and the left atrium which tion and the mycotic aneurysms, and others which are obstructed the outflow of the left coronary artery. The directly related, such as abscess, fistulization or patient died shortly after the operation and in the coronary embolization. necropsy no arteriosclerotic coronary disease was We present the case of a 61-year-old man with no detected. cardiovascular risk factors, and with no previous The abscess is a relatively frequent complication of history of cardiac disease who was admitted to the endocarditis that worsens the prognosis and hospital suffering from acute aortic insufficiency requires surgery in most cases. This complication secondary to pneumococcal aortic endocarditis with favours the fistulization between the cardiac champulmonary edema. bers [1], large vessels [2] or both [3]. On the other The patient was urgently operated on, removing a hand, the thoracic pain during an endocarditis is vegetation of 2 cm in diameter which affected the left usually caused by mechanical complications, an coronary cusp and an abscess which effected the embolism or a coronary obstruction, although on aortic ring. A biological prosthesis was implanted some exceptional occasions the pain could be caused with a good follow-up. by other reasons. In this sense, a case of destruction Several episodes of angina started 11 days later, of the arterial wall and two cases of a external and ST-depression in precordial leads V3–V6 was compression have been reported [4,5]. detected with ECG. The patient also developed signs This patient had a good follow-up after the valve and symptoms of pulmonary oedema. An emergency replacement, but suffered a sudden deterioration with angiocardiography was carried out and in the aortogsevere thoracic pain, probably related to an acute ram, a fistulization from the aortic root to an abscess fistulization and an entering of blood in the abscess (Fig. 1A) adjacent to the left coronary artery was which produced an increase in its volume, pressing seen (Fig. 1B). In the angiography a significant the left coronary artery which caused angina, and stenosis of the left main coronary artery and of the showing severe electrocardiographical changes in the proximal circumflex branch without affecting other ECG. vessels was observed (Fig. 2). This case supports the idea that the hemodynamical The patient was urgently re-operated on, removing disestabilization associated with thoracic pain, and especially when showing changes in the ECG in a patient with endocarditis, could be caused by a direct *Corresponding author. Tel.: 134 8 5106100 Ext. 36261; Fax: 134 8 5274688. effect on the coronary arteries. For this reason, a

Role of Polyamines and cAMP-dependent Mechanisms on 5α-dihydrotestosterone-elicited Functional Effects in Isolated Right Atria of Rat

Androgens produce acute vasodilation of systemic, pulmonary, and coronary arteries in several mammal preparations and increase cardiomyocyte contractility. A decrease of the spontaneous beating of sinoatrial cells has also been described. The aim of this study was to characterize the direct effect of 5α-dihydrotestosterone on the spontaneous chronotropism and inotropism in the same preparation as an approach to establish the effect on cardiac output and their mechanism of action. The effects were studied on isolated right atria of Wistar rats placed in an organ bath in Tyrode solution at 37°C and bubbled with carbogen. In male rats, the acute administration of 5α-dihydrotestosterone, a nonaromatizable derivate of testosterone, elicited a positive inotropism, which was associated with a negative chronotropism. As reported in the left atria, polyamines and β-adrenoceptors played a role in 5α-dihydrotestosterone-elicited positive inotropism because the effect was antagonized by α-difluoromethylornithine, an inhibitor of polyamine synthesis, and atenolol, a β1-adrenoceptor blocker, but not on the negative effect on chronotropism. The androgen increased the sinoatrial node recovery time, suggesting an effect on the mechanisms of spontaneous diastolic depolarization involved in atria pacemaking. These effects of 5α-dihydrotestosterone are not hormonally regulated because they are similarly produced in estrogenized females and gonadectomized male and female rats. These results suggest that the androgen could acutely improve cardiac performance.

Surveillance after cardiac arrest in patients with Brugada syndrome without an implantable defibrillator: An alarm effect of the previous syncope.

BACKGROUND Debate regarding the prognosis of asymptomatic patients with Brugada syndrome (BrS) is possibly affected by the selection bias of survivors of sudden cardiac arrest (SCA). We aimed to determine variables influencing surveillance after SCA. METHODS We analyzed a BrS cohort of 145 patients belonging to 37 families. We compared the clinical data and circumstances surrounding SCA (i.e., place of occurrence and people accompanying the subject) in 10 patients who survived an episode of SCA (Group A) vs. 27 deceased relatives (first or second degree) who suffered sudden cardiac death (SCD; Group B). Information concerning Group B was agreed upon by at least 3 relatives. A sub-analysis was performed considering families carrying a mutation in SCN5A (Group B-Mutant). RESULTS Syncope was unique in predicting SCA in the BrS cohort. Comparing Groups A vs. B, there were no differences in the mean age at time of SCA/SCD (46.2 [SD 17.1] vs. 39.9 [SD 14.5] years; p=0.271), gender (male 60% vs. 74.1%; p=0.442), prior cardiomyopathy (0%), administration of cardiovascular treatments (anti-hypertensive and lipid-lowering drugs; 20% vs. 14.8%; p=0.653) or conventional cardiovascular risk factors. Environmental circumstances surrounding the SCA/SCD were not significantly different between groups. Prior syncope was more frequent in Group A (80% vs. 3.7%; p<0.001) and unique in predicting surveillance (p<0.001). Group B-Mutant displayed equivalent data. CONCLUSIONS A previous syncope, as an alarm symptom, might contribute to better surveillance of SCA compared with subjects with SCA as the debut of BrS. The latter might behave as a factor of selection bias.

Correlation between endogenous polyamines in human cardiac tissues and clinical parameters in patients with heart failure

Polyamines contribute to several physiological and pathological processes, including cardiac hypertrophy in experimental animals. This involves an increase in ornithine decarboxylase (ODC) activity and intracellular polyamines associated with cyclic adenosine monophosphate (cAMP) increases. The aim of the study was to establish the role of these in the human heart in living patients. For this, polyamines (by high performance liquid chromatography) and the activity of ODC and N1‐acetylpolyamine oxidases (APAO) were determined in the right atrial appendage of 17 patients undergoing extracorporeal circulation to correlate with clinical parameters. There existed enzymatic activity associated with the homeostasis of polyamines. Left atria size was positively associated with ODC (r = 0.661, P = 0.027) and negatively with APAO‐N1‐acetylspermine (r = −0.769, P = 0.026), suggesting that increased levels of polyamines are associated with left atrial hemodynamic overload. Left ventricular ejection fraction (LVEF) and heart rate were positively associated with spermidine (r = 0.690, P = 0.003; r = 0.590, P = 0.021) and negatively with N1‐acetylspermidine (r = −0.554, P = 0.032; r = −0.644, P = 0.018). LVEF was negatively correlated with cAMP levels (r = −0.835, P = 0.001) and with cAMP/ODC (r = −0.794, P = 0.011), cAMP/spermidine (r = −0.813, P = 0.001) and cAMP/spermine (r = −0.747, P = 0.003) ratios. Abnormal LVEF patients showed decreased ODC activity and spermidine, and increased N1‐acetylspermidine, and cAMP. Spermine decreased in congestive heart failure patients. The trace amine isoamylamine negatively correlated with septal wall thickness (r = −0.634, P = 0.008) and was increased in cardiac heart failure. The results indicated that modifications in polyamine homeostasis might be associated with cardiac function and remodelling. Increased cAMP might have a deleterious effect on function. Further studies should confirm these findings and the involvement of polyamines in different stages of heart failure.

Ventricular Tachycardia and Early Fibrillation in Patients With Brugada Syndrome and Ischemic Cardiomyopathy Show Predictable Frequency-Phase Properties on the Precordial ECG Consistent With the Respective Arrhythmogenic Substrate

Background—Ventricular fibrillation (VF) has been proposed to be maintained by localized high-frequency sources. We tested whether spectral-phase analysis of the precordial ECG enabled identification of periodic activation patterns generated by such sources. Methods and Results—Precordial ECGs were recorded from 15 ischemic cardiomyopathy and 15 Brugada syndrome (type 1 ECG) patients during induced VF and analyzed in the frequency-phase domain. Despite temporal variability, induced VF episodes lasting 19.6±7.9 s displayed distinctly high power at a common frequency (shared frequency, 5.7±1.1 Hz) in all leads about half of the time. In patients with Brugada syndrome, phase analysis of shared frequency showed a V1–V6 sequence as would be expected from patients displaying a type 1 ECG pattern (P<0.001). Hilbert-based phases confirmed that the most stable sequence over the whole VF duration was V1–V6. Analysis of shared frequency in ischemic cardiomyopathy patients with anteroseptal (n=4), apical (n=3), and inferolateral (n=4) myocardial infarction displayed a sequence starting at V1–V2, V3–V4, and V5–V6, respectively, consistent with an activation origin at the scar location (P=0.005). Sequences correlated with the Hilbert-based phase analysis (P<0.001). Posterior infarction (n=4) displayed no specific sequence. On paired comparison, phase sequences during monomorphic ventricular tachycardia correlated moderately with VF (P<0.001). Moreover, there was a dominant frequency gradient from precordial leads facing the scar region to the contralateral leads (5.8±0.8 versus 5.4±1.1 Hz; P=0.004). Conclusions—Noninvasive analysis of ventricular tachycardia and early VF in patients with Brugada syndrome and ischemic cardiomyopathy shows a predictable sequence in the frequency-phase domain, consistent with anatomic location of the arrhythmogenic substrate.

Primary amyloidosis and syncope

A 59-year-old caucasian consulted our clinic with symptoms of dizziness and exertional syncope. The combination of myocardial hypertrophy diagnosed by echocardiography, together with a history of peripheral neuropathy made us suspect cardiac amyloidosis which was later proven by endomyocardial biopsy. A graded exercise test and two Holter monitoring studies revealed neither rhythm nor conduction abnormalities. A head-up tilt test revealed a vasovagal vasodepressor response.

Differential Responses of the Septal Ventricle and the Atrial Signals during Ongoing Entrainment: A Method to Differentiate Orthodromic Reciprocating Tachycardia using Septal Accessory Pathways from Atypical Atrioventricular Nodal Reentry

Background—Differential diagnosis between tachycardia mediated by septal accessory pathways (AP) and atypical atrioventricular nodal reentry can be challenging. We hypothesized that an immediate versus delayed pace-related advancement of the atrial electrogram, once the local septal parahisian ventricular electrogram (SVE) has been advanced, may help in this diagnosis. Methods and Results—We focused on differential timing between SVE and atrial signals at the initiation of continuous right ventricular apical pacing during tachycardia. SVE advancement preceding atrial reset was defined as SVE advanced by the paced wave fronts while atrial signal continued at the tachycardia cycle. We analyzed 51 atypical atrioventricular nodal reentry (45% posterior type) and 80 AP tachycardias (anteroseptal [10], parahisian [18], midseptal [12], and posteroseptal [40]). SVE advancement preceding atrial reset was observed in 98% of atrioventricular nodal reentries during 4±1.1 cycles; this phenomena was observed in 6 (8%) of the atrioventricular reentrant tachycardia mediated by septal AP (P<0.001; sensitivity 98%; specificity 93%; positive predictive value 90%; negative predictive value 99%) and lasted 1 single cycle (P<0.001). Right posteroseptal AP tachycardias were distinctly characterized by atrial reset preceding SVE advancement (with ventricular fusion; specificity 100%; positive predictive value 100%). In 11 cases, it was impossible to achieve sustain entrainment. In all of them, the differential responses at the entrainment attempt allowed for appropriate diagnosis. Conclusions—The differential response of the SVE and the atrial electrogram at the initiation of continuous right ventricular apical pacing during tachycardia effectively distinguishes between atypical atrioventricular nodal reentry and atrioventricular reentrant tachycardia mediated by septal APs.