Hypertension and cardiac arrhythmias: a review of the epidemiology, pathophysiology and clinical implications

Determining the recurrence rate of premature ventricular complexes and idiopathic ventricular tachycardia after radiofrequency catheter ablation with the help of designing a machine-learning model

Ventricular arrhythmias increase cardiovascular morbidity and mortality. Recurrent PVCs and IVT are generally considered benign in the absence of structural heart abnormalities. Artificial intelligence is a rapidly growing field. In recent years, medical professionals have shown great interest in the potential use of ML, an integral part of AI, in various disciplines, including diagnostic applications, decision-making, prognostic stratification, and solving complex pathophysiological aspects of diseases from these data at extraordinary complexity, scale, and acquisition rate. The aim of this study was to design an ML model to predict the probability of PVC and IVT recurrence after RF ablation. Data of patients were collected and manipulated using traditional analysis and various artificial intelligence models, namely MLP, Gradient Boosting Machines, Random Forest, and Logistic Regression. Hypertension, male sex, and the use of non-irrigate catheters were associated with less freedom from arrhythmia. All these results were obtained through traditional analytic methods, and according to AI, none of the variables had a clear effect on the recurrence of arrhythmia. Each AI model presents unique strengths and weaknesses, and further optimization and fine-tuning of these models are necessary to increase their clinical utility. By expanding the dataset, improved predictions can be fostered to ultimately increase the clinical utility of AI in predicting PVC erosion outcomes.

Clinical Profiles and One-Year Outcome in Middle Eastern Patients With Atrial Fibrillation and Hypertension: Analysis From the Jordan Atrial Fibrillation Study

Studies on the impact of hypertension (HTN) on the outcome of patients with atrial fibrillation (AF) in the Middle East are scarce. The aim of this contemporary multicenter study is to evaluate the effect of the coexisting HTN on the baseline clinical profiles and 1-year prognosis in a cohort of Middle Eastern patients with AF. Consecutive AF patients in 29 hospitals and cardiology clinics were enrolled in the Jordan AF study (May 2019-December 2020). Patients were prospectively followed up for 1 year, and the study had no influence on their treatment, which was at the discretion of the treating physician. We compared clinical features, use of medications, and 1-year prognosis in patients with AF/HTN compared with AF/no HTN. Among 1849 non-valvular AF patients, 76.4% had HTN, with higher prevalence of diabetes, dyslipidemia, coronary heart disease, stroke, and left ventricular hypertrophy in HTN patients. There was a higher thromboembolic and bleeding risk among HTN patients. At 1 year, HTN patients had significantly higher rates of stroke and systemic embolism (SSE) (4.5%), acute coronary syndrome (ACS) (2.4%), rehospitalization (27.9%), and major bleeding events (3.0%) compared with non-HTN patients. In this cohort, the coexistence of HTN was associated with worse baseline clinical profile and 1-year outcomes.

Cardiac arrhythmias in STEMI patients in ICU: study on occurrence in first 48 h and correlation with age, sex, infarction site, and risk factors

Introduction

Acute myocardial infarction (AMI) is one of the leading causes of death in the developed world. The spread of the disease approaches three million people worldwide, with more than one million deaths in the United States annually. Myocardial ischemia and infarction can lead to electrophysiological and metabolic alterations that result in potentially fatal arrhythmias, some of which may be asymptomatic. About 90% of patients with AMI develop some form of arrhythmia during or immediately after the event, and in 25% of patients, these arrhythmias appear within the first 48 h. The most common cause of death in patients with AMI in pre-hospitalization is ventricular tachycardia/ventricular fibrillation (VT/VF).

Methods

A cross-sectional study targeting 150 patients with myocardial infarction attending tertiary hospital. According to certain acceptance and exclusion criteria.

Results

The sample consisted of 150 patients who suffered from heart infarction, the mean age of patients in the sample was 59.41 years with a standard deviation of 11.02 years and range of 28-90. Males constituted the largest portion of patients, with 112 males, that is 75%. The study identified that the anterior wall was the most frequent location for myocardial infarction among patients, with 64% of patients experiencing an infarction in this area. Additionally, ventricular fibrillation was the most commonly occurring arrhythmia, affecting 27% of myocardial infarction patients in the study.

Recommendations

One of the most important recommendations of our study is the necessity of keeping the patient under observation for at least 48 h after myocardial infarction within the hospital to monitor the ECG (Holter) in order to detect arrhythmias. Detection of arrhythmias in every patient with extensive anterior, lateral, or posterior myocardial infarction. And the need to know and take into account ventricular fibrillation and how to manage it in every patient with a heart infarction. And conducting future studies, including a larger number of patients, to study cardiac arrhythmias more precisely.

Ventrikuläre Arrhythmien bei obstruktiver und zentraler Schlafapnoe

Hintergrund

Ventrikuläre Arrhythmien treten mit einer hohen Prävalenz auf und sind mit einer hohen Morbidität und Mortalität assoziiert. Sowohl die obstruktive (OSA) als auch die zentrale (ZSA) Schlafapnoe können auf Grund ihrer Pathophysiologie zu vermehrten ventrikulären Arrhythmien beitragen.

Ziel

Dieser Artikel soll die komplexen Zusammenhänge und Erkenntnisse jüngster Forschungen bezüglich schlafbezogenen Atmungsstörungen (SBAS) und ventrikulärer Arrhythmien und deren Therapiemöglichkeiten beleuchten.

Material und Methoden

Es erfolgte eine Literaturrecherche basierend auf prospektiven, retrospektiven, klinischen und experimentellen Studien sowie Reviews, Metaanalysen und aktuellen Leitlinien, die seit 2014 in der Medline-Datenbank gelistet wurden.

Ergebnisse

Es besteht ein bidirektionaler Zusammenhang zwischen der SBAS und ventrikulären Arrhythmien. Intermittierende Hypoxie, oxidativer Stress, wiederkehrende Arousals, intrathorakale Druckschwankungen und kardiales Remodeling tragen im Rahmen der SBAS zu einer erhöhten ventrikulären Arrhythmieneigung bei. Der Schweregrad der OSA, gemessen mittels Apnoe-Hypopnoe-Index, ist mit der Prävalenz ventrikulärer Arrhythmien assoziiert. Ähnliche Ergebnisse liegen für Patienten mit ZSA und Herzinsuffizienz vor. Studien zu ventrikulären Arrhythmien bei ZSA-Patienten ohne Herzinsuffizienz fehlen. Eine Positivdrucktherapie (PAP) bei OSA- oder ZSA-Patienten führte in verschiedenen Studien zu einer reduzierten Anzahl an ventrikulären Arrhythmien. Dieser Zusammenhang konnte jedoch nicht in allen Studien bestätigt werden. Ventrikuläre Arrhythmien treten bei der OSA gehäuft nachts auf, bei der ZSA gleichmäßig über den Tag verteilt.

Diskussion

Bisherige Studien weisen einen Zusammenhang zwischen der OSA bzw. der ZSA und ventrikulären Arrhythmien trotz unterschiedlicher Pathophysiologie nach. Hinsichtlich des Effektes der PAP auf ventrikuläre Arrhythmien bei Patienten mit OSA und ZSA sind weitere Studien erforderlich.

Electrical Features of the Diabetic Myocardium. Arrhythmic and Cardiovascular Safety Considerations in Diabetes

Diabetes is a chronic metabolic disease characterized by hyperglycemia in the absence of treatment. Among the diabetes-associated complications, cardiovascular disease is the major cause of mortality and morbidity in diabetic patients. Diabetes causes a complex myocardial dysfunction, referred as diabetic cardiomyopathy, which even in the absence of other cardiac risk factors results in abnormal diastolic and systolic function. Besides mechanical abnormalities, altered electrical function is another major feature of the diabetic myocardium. Both type 1 and type 2 diabetic patients often show cardiac electrical remodeling, mainly a prolonged ventricular repolarization visible in the electrocardiogram as a lengthening of the QT interval duration. The underlying mechanisms at the cellular level involve alterations on the expression and activity of several cardiac ion channels and their associated regulatory proteins. Consequent changes in sodium, calcium and potassium currents collectively lead to a delay in repolarization that can increase the risk of developing life-threatening ventricular arrhythmias and sudden death. QT duration correlates strongly with the risk of developing torsade de pointes, a form of ventricular tachycardia that can degenerate into ventricular fibrillation. Therefore, QT prolongation is a qualitative marker of proarrhythmic risk, and analysis of ventricular repolarization is therefore required for the approval of new drugs. To that end, the Thorough QT/QTc analysis evaluates QT interval prolongation to assess potential proarrhythmic effects. In addition, since diabetic patients have a higher risk to die from cardiovascular causes than individuals without diabetes, cardiovascular safety of the new antidiabetic drugs must be carefully evaluated in type 2 diabetic patients. These cardiovascular outcome trials reveal that some glucose-lowering drugs actually reduce cardiovascular risk. The mechanism of cardioprotection might involve a reduction of the risk of developing arrhythmia.

Coronary heart disease and atrial fibrillation: a vicious cycle

The population suffering from coronary heart disease (CHD) complicated by atrial fibrillation (AF) is rising rapidly. A strong correlation between the two diseases has been reported, and the many common risk factors they share may play prominent roles in their development. In addition, CHD can directly promote the progression of AF by affecting reentry formation, focal ectopic activity, and neural remodeling. At the same time, AF also affects CHD through three aspects: 1) atherosclerosis, 2) the mismatch of blood supply and oxygen consumption, and 3) thrombosis. In conclusion, CHD and AF can aggravate each other and seem to form a vicious cycle. For patients with CHD complicated by AF, principal studies and guidelines have focused on antithrombotic treatment and rhythm control, which are paramount for these patients. Of note, our review sheds light on the strategies to break the cycle of the two diseases, which may be fundamental to treat these patients and optimize the benefit.

Sudden Arrhythmic Death at the Higher End of the Heart Failure Spectrum

The risk of sudden cardiac death (SCD) is high in heart failure (HF) patients. Sudden arrhythmic death (SAD) is a frequent cause of exit in HF patients at the lower end of the HF spectrum, and implantable cardioverter–defibrillators have been recommended to prevent these life-threatening rhythm disturbances in select patients. However, less is known regarding the cause of SCD in patients at the upper end of the HF spectrum, despite the fact that the majority of out-of-hospital SCD victims have unknown or near-normal/normal left ventricular ejection fraction (LVEF). In this review, we report the epidemiology, summarize the mechanisms, discuss the diagnostic challenges, and propose a stepwise approach for the prevention of SAD in HF with near-normal/normal LVEF.

Ciliotherapy: Remote Control of Primary Cilia Movement and Function by Magnetic Nanoparticles

Patients with polycystic kidney disease (PKD) are characterized with uncontrolled hypertension. Hypertension in PKD is a ciliopathy, an abnormal function and/or structure of primary cilia. Primary cilia are cellular organelles with chemo and mechanosensory roles. In the present studies, we designed a cilia-targeted (CT) delivery system to deliver fenoldopam specifically to the primary cilia. We devised the iron oxide nanoparticle (NP)-based technology for ciliotherapy. Live imaging confirmed that the CT-Fe₂O₃-NPs specifically targeted primary cilia in cultured cells in vitro and vascular endothelia in vivo. Importantly, the CT-Fe₂O₃-NPs enabled the remote control of the movement and function of a cilium with an external magnetic field, making the nonmotile cilium exhibit passive movement. The ciliopathic hearts displayed hypertrophy with compromised functions in left ventricle pressure, stroke volume, ejection fraction, and overall cardiac output because of prolonged hypertension. The CT-Fe₂O₃-NPs significantly improved cardiac function in the ciliopathic hypertensive models, in which the hearts also exhibited arrhythmia, which was corrected with the CT-Fe₂O₃-NPs. Intraciliary and cytosolic Ca²⁺ were increased when cilia were induced with fluid flow or magnetic field, and this served as a cilia-dependent mechanism of the CT-Fe₂O₃-NPs. Fenoldopam-alone caused an immediate decrease in blood pressure, followed by reflex tachycardia. Pharmacological delivery profiles confirmed that the CT-Fe₂O₃-NPs were a superior delivery system for targeting cilia more specifically, efficiently, and effectively than fenoldopam-alone. The CT-Fe₂O₃-NPs altered the mechanical properties of nonmotile cilia, and these nano-biomaterials had enormous clinical potential for ciliotherapy. Our studies further indicated that ciliotherapy provides a possibility toward personalized medicine in ciliopathy patients.

Hypertension and cardiac arrhythmias: a consensus document from the European Heart Rhythm Association (EHRA) and ESC Council on Hypertension, endorsed by the Heart Rhythm Society (HRS), Asia-Pacific Heart Rhythm Society (APHRS) and Sociedad Latinoamericana de Estimulación Cardíaca y Electrofisiología (SOLEACE)

Hypertension is a common cardiovascular risk factor leading to heart failure (HF), coronary artery disease, stroke, peripheral artery disease and chronic renal insufficiency. Hypertensive heart disease can manifest as many cardiac arrhythmias, most commonly being atrial fibrillation (AF). Both supraventricular and ventricular arrhythmias may occur in hypertensive patients, especially in those with left ventricular hypertrophy (LVH) or HF. Also, some of the antihypertensive drugs commonly used to reduce blood pressure, such as thiazide diuretics, may result in electrolyte abnormalities (e.g. hypokalaemia, hypomagnesemia), further contributing to arrhythmias, whereas effective control of blood pressure may prevent the development of the arrhythmias such as AF. In recognizing this close relationship between hypertension and arrhythmias, the European Heart Rhythm Association (EHRA) and the European Society of Cardiology (ESC) Council on Hypertension convened a Task Force, with representation from the Heart Rhythm Society (HRS), Asia-Pacific Heart Rhythm Society (APHRS), and Sociedad Latinoamericana de Estimulación Cardíaca y Electrofisiología (SOLEACE), with the remit to comprehensively review the available evidence to publish a joint consensus document on hypertension and cardiac arrhythmias, and to provide up-to-date consensus recommendations for use in clinical practice. The ultimate judgment regarding care of a particular patient must be made by the healthcare provider and the patient in light of all of the circumstances presented by that patient.

Effects of Trypanosoma brucei brucei infection and diminazene aceturate administration on the blood pressure, heart rate, and temperature of Wistar albino rats

BACKGROUND

This study was carried out to determine the blood pressure changes in experimentally Trypanosoma brucei brucei-infected Wistar albino rats and diminazene aceturate-treated rats.

METHODS

Twenty-four rats were purchased and divided into four groups consisting of six rats each. Control group (CON) received 0.5 mL of distilled water, i.m., infected but not treated group (INF) received 2×106 trypanosome/mL i.m., infected but diminazene aceturate-treated group (INFDIM) received 2×106 trypanosome/mL, 3.5 mg/kg, i.m.) and non-infected but diminazene aceturate-treated group (DIM) received 3.5 mg/kg, i.m. and served as negative control. The blood pressures were measured using a CODA 2® non-invasive blood pressure monitor (Kent Scientific, USA). The results were compiled and statistical analysis was done with significance set at p≥0.05.

RESULTS

The values of the blood pressure readings of the Trypanosoma-infected INF (137.0±2.0 mmHg) and diminazene-treated rats INFDIM (125.0±7.5 mmHg) when compared to the control group (168.0±3.0 mmHg) were significantly lower (p≤0.05) at the end of day 7. The heart rate was also significantly reduced in the INF (403.5±1.5 beats/min) and DIM (445.0±24 beats/min) groups of rats when compared with the control group (613.0±2.0 beats/min) at the end of day 8.

CONCLUSION

The findings indicate the significant reduction in blood pressure and heart rates during Trypanosoma brucei brucei infection and with diminazene aceturate administration. Hence, caution should be exercised when treating trypanosome-infected patients with diminazene aceturate.

High resolution 3-Dimensional imaging of the human cardiac conduction system from microanatomy to mathematical modeling

Cardiac arrhythmias and conduction disturbances are accompanied by structural remodelling of the specialised cardiomyocytes known collectively as the cardiac conduction system. Here, using contrast enhanced micro-computed tomography, we present, in attitudinally appropriate fashion, the first 3-dimensional representations of the cardiac conduction system within the intact human heart. We show that cardiomyocyte orientation can be extracted from these datasets at spatial resolutions approaching the single cell. These data show that commonly accepted anatomical representations are oversimplified. We have incorporated the high-resolution anatomical data into mathematical simulations of cardiac electrical depolarisation. The data presented should have multidisciplinary impact. Since the rate of depolarisation is dictated by cardiac microstructure, and the precise orientation of the cardiomyocytes, our data should improve the fidelity of mathematical models. By showing the precise 3-dimensional relationships between the cardiac conduction system and surrounding structures, we provide new insights relevant to valvar replacement surgery and ablation therapies. We also offer a practical method for investigation of remodelling in disease, and thus, virtual pathology and archiving. Such data presented as 3D images or 3D printed models, will inform discussions between medical teams and their patients, and aid the education of medical and surgical trainees.

Heart rate variability and arrhythmic patterns of 24-hour Holter electrocardiography among Nigerians with cardiovascular diseases

BACKGROUND

Facilities for Holter electrocardiography (ECG) monitoring in many Nigerian hospitals are limited. There are few published works in Nigeria on the use of 24-hour Holter ECG in cardiac arrhythmic evaluation of patients with cardiovascular diseases.

OBJECTIVE

To study the clinical indications, arrhythmic pattern, and heart rate variability (HRV) among subjects referred for 24-hour Holter ECG at our Cardiac Care Unit.

METHODS

Three-hundred and ten patients (134 males and 176 females) were studied consecutively over a 48-month period using Schiller type (MT-101) Holter ECG machine.

RESULTS

Out of the 310 patients reviewed, 134 were males (43.2%) and 176 were females (56.8%). The commonest indication for Holter ECG was palpitation followed by syncope in 71 (23%) and 49 (15.8%) of subjects, respectively. Premature ventricular complex and premature atrial complex were the commonest types of arrhythmia in 51.5% and 15% subjects, respectively. Ventricular arrhythmia was more prevalent in dilated cardiomyopathy patients (85.7%). The HRV of subjects with palpitation, stroke, and diabetes mellitus with autonomic neuropathy, using standard deviation of normal to normal intervals average (milliseconds), were 107.32±49.61, 79.15±49.15, and 66.50±15.54, respectively. The HRV, using standard deviation of averages of normal to normal intervals average (milliseconds), of patients with palpitation, stroke, and diabetes mellitus with autonomic neuropathy were 77.39±62.34, 57.82±37.05, and 55.50±12.71, respectively.

CONCLUSION

Palpitation and syncope were the commonest indications for Holter ECG among our subjects. The commonest arrhythmic patterns were premature ventricular complex and premature atrial complex, with ventricular arrhythmia being more prevalent in dilated cardiomyopathy. There was a reduction in HRV in patients with stroke and diabetic autonomic neuropathy.

Left ventricular mass and the risk of sudden cardiac death: a population-based study

BACKGROUND

Left ventricular (LV) mass ascertained using echocardiography may enhance risk stratification for sudden cardiac death. The objective of this study was to assess the association between left ventricular mass and the risk of sudden cardiac death in a population-based cohort and determine its incremental value beyond conventional risk predictors.

METHODS AND RESULTS

Assessment of LV mass was based on echocardiography in a sample of 905 middle-aged men representative of the general population (aged 42 to 61 years). During the follow-up period of 20 years, there were a total of 63 sudden cardiac deaths. In a comparison of the top versus the bottom quartile of LV mass adjusted by body surface area (>120 versus <89 g/m(2)), the multivariable adjusted hazard ratio was 2.57 (95% CI 1.24 to 5.31, P=0.010). Further adjustment for LV function only modestly attenuated the risk of sudden cardiac death among men with LV mass of >120 g/m(2) (hazard ratio 2.29, 95% CI 1.10 to 4.74, P=0.026). Addition of LV mass adjusted by body surface area to a conventional risk factor model for sudden cardiac death improved the integrated discrimination index by 0.033 (95% CI 0.009 to 0.057, P=0.007) and the category-free net reclassification index by 0.501 (95% CI 0.092 to 0.911, P=0.016).

CONCLUSIONS

Indexed LV mass by body surface area is an independent predictor of sudden cardiac death and may help improve the risk prediction of sudden cardiac death beyond conventional cardiovascular risk factors.

Valvular regurgitations may increase risk of arrhythmias in Nigerians with hypertensive heart failure

BACKGROUND

Hypertensive heart disease (HHD) is the commonest cause of sudden cardiac death among Nigerians. A high frequency and early onset of valvular regurgitations (VHD) in hypertensives, and greater concentric hypertrophy are also common in that population.

AIMS AND METHODS

To further investigate the relationship between VHD and cardiac arrhythmias and their correlates seen in the hypertensive spectrum and to test the hypothesis that VHD predisposes to cardiac arrhythmias in hypertensive heart failure (HHF). HHF patients (n = 14), HHD patients n = 23, and normotensive controls (n = 9) all underwent 24 h electrocardiogram Holter monitoring as well as two-dimensional and Doppler echocardiography. Participants in each patient category were classified according to the presence and severity of VHD or its absence (NVHD).

RESULTS

There were statistically significant differences in the mean supraventricular tachycardia (SVT) (P < 0.001 analysis of variance; ANOVA), the mean and median frequency of ventricular tachycardia episodes (P < 0.02 ANOVA), and couplets (P = 0.0002 ANOVA) between groups. HHF-VHD always had more SVT (81/24 versus 4.4/24 h; P = 0.016) and ventricular arrhythmias 69/24 versus 34/24 h (P < 0.02) than HHF-NVHD. Multivalvular regurgitations (three or more valves), higher left ventricular mass index (g/m2) [274 (24) versus 191(19); P < 0.001 ANOVA], and lower ejection fraction (EF; %) [29(3) versus 53(14)] in HHF-VHD were arrhythmogenic. Mean ventricular tachycardia/triplet frequency/24 h were HHF-VHD 69, HHF-NVHD 39, HHD-VHD 0.3, HHD-NVHD 6, and controls 0.2 (P < 0.02 ANOVA). Compared with 35% (10/27) of all VHD, 15.7% (3/19) of all NVHD participants had nonsustained ventricular tachycardia. The number of regurgitant valves was positively correlated with the frequency of the Lown class of the arrhythmias 0-IVB (r = 0.42, P = 0.003) and to ventricular tachycardia (r = 0.3, P = 0.04) (both n = 46).

CONCLUSION

Left ventricular hypertrophy (LVH) increased arrhythmias. But multivalvular regurgitations predisposes to greater SVT and complex ventricular arrhythmias, especially in HHF. Low EF and concentric LVH are correlates.

Hypertension increases with aging and obesity in chimpanzees (Pan troglodytes)

Cardiovascular disease is a primary cause of morbidity and mortality in captive chimpanzees. Four years of blood pressure (BP) data were analyzed from a captive former laboratory population of 201 healthy adult chimpanzees with assessment of age and obesity on elevated BP. Five different measures of obesity were compared: abdominal girth, basal metabolic rate, body-mass index (BMI), body weight, and surface area. Systolic BP varied by sex. Obesity did not influence male BP. For females, obesity was a significant determinant of BP. The best measure of female obesity was basal metabolic rate and the worst was BMI. Median systolic BP of healthy weight females (<54.5 kg) was significantly lower (128 mmHg) than overweight or obese females (140 mmHg), but both were lower than all males (147 mmHg). For diastolic BP, neither sex nor any of the five obesity measures was significant. But age was highly significant, with geriatric chimpanzees (>30 years) having higher median diastolic BP (74 mmHg) than young adults of 10-29 years of age (65 mmHg). By these criteria, 80% of this population is normotensive, 7% prehypertensive, and 13% hypertensive. In summary, systolic BP intervals required adjustment for obesity among females but not males. Diastolic BP required adjustment for advanced age (≥30 years). Use of these reference intervals can facilitate timely clinical care of captive chimpanzees.

Relation of systemic blood pressure to sudden cardiac death

The role of systolic blood pressure (SBP) as an independent risk factor for sudden cardiac death (SCD) is not well defined in a general population. Thus, we assessed the association between BP at rest and risk of SCD. BP and other risk factors were measured in a representative population-based sample of 2,666 Finnish men (42 to 61 years of age). During an average follow-up period of 18.9 years (interquartile range 17.9 to 22.6), 213 SCDs occurred. Each increment 10-mm Hg of SBP at rest was associated with an increased risk of SCD (relative hazard 1.15, 95% confidence interval 1.07 to 1.25, p <0.001) after adjustment for age, alcohol consumption, cigarette smoking, serum low-density lipoprotein cholesterol, type 2 diabetes, body mass index, left ventricular hypertrophy, previous myocardial infarction, family history of coronary heart disease, and use of antihypertensive medications. Men with increased SBP of >145 mm Hg had a 2.04-fold (95% confidence interval 1.23 to 2.52, p = 0.003) adjusted risk for SCD compared to those with SBP <123 mm Hg. In conclusion, this study emphasizes the importance of the definition of SBP at rest because it provides a valuable prognostic measurement for SCD.

Pressure overload

This review discusses cardiac consequences of pressure overload. In response to elevated pressure, the ventricular hypertrophy compensates for the increased wall stress. However, the ventricular hypertrophy involves numerous structural adaptations that may lead to ventricular dysfunction and, eventually, heart failure. Particular emphasis is placed on molecular mechanisms that govern the development of hypertrophy and that may lead to maladaptive structural changes resulting in adverse cardiac events.

Increased late sodium current in left atrial myocytes of rabbits with left ventricular hypertrophy: its role in the genesis of atrial arrhythmias

Left ventricular hypertrophy (LVH) is frequently associated with clinical atrial arrhythmias, but little is known about how it causes those arrhythmias. Our previous studies have shown that LVH increases the late sodium current (I(Na-L)) that plays an important role in the genesis of ventricular arrhythmias. We hypothesize that LVH may also induce an upregulation of the I(Na-L) in atrial myocytes, leading to atrial electrical abnormalities. The renovascular hypertension model was used to induce LVH in rabbits. Action potential and membrane current recordings were performed in single myocytes. At a pacing cycle length of 2,000 ms, spontaneous phase-2 early afterdepolarizations (EADs) could be recorded from the left atrial myocytes in 10 of 12 LVH rabbits, whereas no EADs could be elicited in right atrial myocytes of LVH rabbits or atrial myocytes from any of the 12 control rabbits. Spontaneous automaticity (SA) from left atrial myocytes was observed in 9 out of 12 LVH rabbits, but none in right atrial myocytes of LVH rabbits or control rabbits, at a pacing rate of 8,000 ms. The left atrial myocytes of LVH rabbits had a significantly higher density of the I(Na-L) compared with those of control rabbits (0.90 +/- 0.12 in LVH vs. 0.50 +/- 0.08 pA/pF in control, n = 8, P < 0.01). Tetrodotoxin, an I(Na-L) blocker, abolished all atrial EADs and SA at 10 microM. Our results demonstrate that LVH induction results in a significant increase of I(Na-L) in the left atrial myocytes that may render these cells susceptible to the genesis of EADs and SA. The I(Na-L) may serve as a potentially useful ionic target for antiarrhythmic drugs for the treatment of atrial arrhythmias in the setting of LVH.