Pulsus alternans determined by biventricular simultaneous systolic time intervals

Comparison of patients with pulmonary arterial hypertension with versus without right-sided mechanical alternans

The clinical implications of mechanical alternans in patients with pulmonary arterial hypertension (PAH) remain unknown. In this study, the prevalence, characteristics, and prognostic implications of mechanical alternans in patients with PAH were investigated. Thirty-two consecutive patients with PAH confirmed by cardiac catheterization from 2000 to 2010 were included in this cohort study. During cardiac catheterization, 8 patients (25%) showed mechanical alternans at rest. All alternans were detected in the right ventricle and pulmonary trunk. Serum level of brain natriuretic peptide (584 ± 177 vs 238 ± 252 pg/ml, p = 0.001), World Health Organization functional class (3.5 ± 0.5 vs 2.9 ± 0.4, p = 0.02), mean pulmonary arterial pressure (59 ± 10 vs 47 ± 18 mm Hg, p = 0.03), mean right atrial pressure (10 ± 4 vs 5 ± 4 mm Hg, p = 0.01), right ventricular end-diastolic pressure (15 ± 5 vs 9 ± 5 mm Hg, p = 0.01), and heart rate at catheterization (96 ± 17 vs 70 ± 11 beats/min, p = 0.003) were significantly higher in patients with alternans than in those without. Twelve-month mortality of patients with alternans was higher than in patients without alternans (p = 0.03): the 12-month survival rate after cardiac catheterization was 37% for the alternans group and 75% for the group without alternans. In conclusion, isolated right-sided mechanical alternans is not an uncommon event in patients with PAH. The existence of alternans is associated with the severity of PAH and right ventricular dysfunction and implies a poor prognosis in the short term.

Pulsus alternans in English cocker spaniels with dilated cardiomyopathy

OBJECTIVES

To report the clinical findings associated with pulsus alternans in English cocker spaniels with dilated cardiomyopathy and to review the phenomenon of mechanical alternans, usually found in patients with severe left ventricular systolic dysfunction.

METHODS

The case records of 10 English cocker spaniels with dilated cardiomyopathy and pulsus alternans were reviewed. All dogs had been referred in moderate to severe congestive heart failure. Pulsus alternans was clinically recognised by palpation of a regular alternation of femoral pulse amplitude and confirmed by echocardiography in all cases. Pulsus alternans was an intermittent finding in all 10 dogs.

RESULTS

Phonocardiographic recordings were obtained in three dogs to document variation in the intensity of the heart sounds, with one case exhibiting absence of the second heart sound in alternate beats. M-mode echocardiography performed in all dogs showed alternation of the pattern of mitral valve diastolic motion. Doppler echocardiography showed marked alternation in stroke volume in the aortic outflow in all cases. It also showed alternation in mitral regurgitation and in the velocity of early ventricular filling.

CLINICAL SIGNIFICANCE

Pulsus alternans may be more prevalent in English cocker spaniels than in other breeds, and because of its intermittent nature, its incidence may be higher than that previously reported. It has diagnostic relevance as it usually indicates severe myocardial depression. Echocardiography allows non-invasive detection of mechanical alternans and provides further insights into its pathophysiology and clinical significance.

Arterial and Left Ventricular Pressures Illude Transient Alternans of Contractility during Postextrasystolic Potentiation

We have previously found that the postextrasystolic (PES) potentiation (PESP) of the left ventricular (LV) contractility (Emax) decays typically in transient alternans even in the normally ejecting canine heart. This contradicted the general expectation that arterial pressure (AP) and LV pressure (LVP) usually decay exponentially during PESP. We hypothesized this contradiction to be due to the different cardiodynamic behaviors of AP and LVP from LV Emax during PESP. We tested this hypothesis by measuring AP, LVP, LV volume, Emax, effective arterial elastance (Ea) as an index of afterload, and pulse pressure (PP) during PESP in eight anesthetized open-chest dogs by using the conductance catheter system. We changed Ea by changing the total peripheral resistance (TPR) with methoxamine hydrochloride (iv) and repeated the measurements. Although the Emax alternans patterns during PESP were comparable between the normal and high afterloads, LVP and PP were slightly potentiated and alternated under the normal afterload, whereas LVP and PP were obviously potentiated and alternated under the high afterload. We also simulated the effects of Ea/Emax on the transient alternans of AP and LVP on a computer. Despite the same alternans pattern of Emax, a higher Ea/Emax, which is typical in heart failure, caused a larger PP alternans, whereas a lower Ea/Emax, which is typical in normal hearts, almost eliminated it. These results suggest that a transient alternans of LV contractility during PESP could be overlooked when AP and LVP are monitored in in situ normal hearts.

Postextrasystolic regulation patterns of blood pressure and heart rate in patients with idiopathic dilated cardiomyopathy

Assessment of fluctuations in heart rate (HR) following a premature ventricular complex (PVC) is valuable for identifying patients at high risk of sudden cardiac death. We hypothesised that postextrasystolic potentiation is the main determinant of the regulation patterns of blood pressure (BP) and HR following a PVC. Twelve patients with idiopathic dilated cardiomyopathy (IDC) and 13 control subjects with single PVCs (comparable coupling intervals) were investigated. Non-invasive finger arterial BP and ECGs were analysed. Regulation patterns following a single PVC were quantified using the indices postextrasystolic amplitude potentiation (PEAP) and maximum turbulence slope of five consecutive mean BP values (MBP-TS), and compared with the HR turbulence parameters turbulence slope (HR-TS) and turbulence onset (HR-TO). PEAP was significantly higher in IDC patients compared to controls (48.7 +/- 32.6 vs. 9.8 +/- 5.4 %, P < 0.01), whereas MBP-TS was lower (0.97 +/- 0.60 vs. 2.07 +/- 1.04 mmHg BBI(-1) (BBI, beat-to-beat interval), P < 0.05), as was HR-TS (8.46 +/- 7.90 vs. 30.73 +/- 22.90 ms BBI(-1), P < 0.01). HR-TO was significantly higher in IDC patients (-0.56 +/- 2.19 vs. -5.52 +/- 4.13 %, P < 0.01). In addition, the regulation patterns of BP and HR following a single PVC differed significantly between IDC patients and controls. Specifically, we observed pronounced PEAPs in IDC patients. The baroreflex response initiated by the low pressure amplitude of the PVC was suppressed in IDC patients due to the augmented potentiation of the first postextrasystolic blood pressure. Furthermore, IDC patients displayed impressive postextrasystolic pulsus alternans phenomena, whereas healthy subjects exhibited a typical baroreflex pattern. The pulsus alternans phenomenon seems to be triggered by a PVC.

Mechanical alternans in patients with chronic heart failure

BACKGROUND

Clinical implications of mechanical alternans in patients with chronic heart failure have remained uncertain. In this study, prevalence, characteristics, and prognostic implications of mechanical alternans were investigated.

METHODS AND RESULTS

Consecutive 51 patients with dilated cardiomyopathy underwent diagnostic cardiac catheterization using a micromanometer-tipped catheter. Under basal conditions, 7 of 35 patients with sinus rhythm showed mechanical alternans. Physiologic tachycardia (110 bpm) induced mechanical alternans in another 15 patients with sinus rhythm and in another 10 of 16 patients with atrial fibrillation. Low doses of dobutamine also induced mechanical alternans in another 8 patients, but a high dose of dobutamine eliminated mechanical alternans. Consequently, 40 patients (78%) showed mechanical alternans. Mechanical alternans was always accompanied by alternating changes of positive dP/dt, a parameter of contractility during isovolumetric contraction time, but negative dP/dt was occasionally constant. Concordant mechanical alternans between both ventricles was more prevalent than discordant alternans. The left ventricular end-diastolic volume indices and end-systolic volume indices of patients with mechanical alternans were larger than those of patients without. The left ventricular ejection fraction of patients with alternans was significantly lower than that of patients without.

CONCLUSIONS

Mechanical alternans was highly prevalent in patients with chronic heart failure. The origin of mechanical alternans seems to exist before or at the isovolumetric contraction time.

Right-sided pulsus alternans in diastolic left ventricular dysfunction

Pulsus alternans is usually found in patients with reduced systolic ventricular function. We describe a patient with shortness of breath, hypertension, and left ventricular hypertrophy, but with normal left and right systolic function. Pulsus alternans was demonstrated in the pulmonary wedge position, pulmonary artery, and right ventricle, but not in the aorta or left ventricle. Cathet. Cardiovasc. Intervent. 47:336-339, 1999.

Left ventricular diastolic pulsus alternans in hypertrophic cardiomyopathy

We examined left ventricular (LV) diastolic pulsus alternans associated with systolic pulsus alternans in a patient with hypertrophic cardiomyopathy. Alternation in abnormal LV diastolic pressure waveforms persistently declining into mid-diastole (incomplete relaxation) and normal diastolic pressure were noted. Diastolic pulsus alternans was not corrected by isoproterenol and may possibly be independent of systolic pulsus alternans.

Cardiac alternans: diverse mechanisms and clinical manifestations

OBJECTIVES

The purpose of this review is to assemble the widely dispersed information about cardiac alternans and to categorize the types and mechanisms of alternans, their clinical manifestations and possible therapeutic implications.

BACKGROUND

The phenomena of mechanical and electrical alternans have been of continuing interest to both physiologists and clinicians. Recent studies have enhanced this interest because of the reported association of alternans with experimental myocardial ischemia and cardiac arrhythmias.

METHODS

The review formulates concepts based on extensive review of published studies and personal observations.

RESULTS

Cardiac alternans has been subdivided into the following four categories: 1) mechanical, 2) electrical, 3) in association with myocardial ischemia, and 4) in association with cardiac motion. Mechanical alternans can be explained by hemodynamic or inotropic alterations, or both. Mechanical alternans in the ventricular muscle is accompanied by alternans of action potential shape. In the Purkinje fibers, action potential duration alternates without change in shape and is determined by the duration of the preceding diastolic interval. However, in ventricular muscle fiber, alternans can occur in the presence of constant diastolic intervals. T wave alternans reflects changes in action potential duration and is frequently associated with a long QT interval. Electrocardiographic manifestations of conduction alternans occur at many different sites within the conducting system and myocardium. During myocardial ischemia, additional mechanisms of repolarization alternans have been proposed. Alternans occurring in the presence of a large pericardial effusion is attributed to swinging motion of the heart maintaining two-beat periodicity.

CONCLUSIONS

Since its origin as "pulsus alternans" described by Traube in 1872, the definition of alternans has evolved into a term encompassing multiple physiologic and pathologic phenomena that, although united by the term cardiac alternans, diverge widely with respect to etiology, mechanism and clinical significance.

Clinical and hemodynamic characteristics of patients with inducible pulsus alternans

Pulsus alternans can be found in some patients with abnormal left ventricular function and also can develop after spontaneous premature beats. The purposes of this study were to: (1) determine the inducibility of pulsus alternans in a series of patients referred for routine cardiac catheterization and (2) define the clinical and hemodynamic characteristics of those who develop pulsus alternans. In 104 patients referred for right and left heart catheterization, atrial premature beats and rapid atrial pacing were used to try to provoke pulsus alternans. The 29 patients who developed pulsus alternans in response to these maneuvers were older (63 +/- 6 vs 59 +/- 10 years, p less than 0.01) and had a greater incidence of valvular heart disease (45% vs 23%, p less than 0.01) and congestive heart failure (38% vs 17%, p less than 0.05). Aortic stenosis was the most prevalent valve lesion found. Those who developed pulsus alternans in response to pacing were further characterized by higher left ventricular systolic (143 +/- 42 vs 121 +/- 23 mm Hg, p less than 0.02) and end-diastolic pressures (17 +/- 9 vs 13 +/- 6 mm Hg, p less than 0.05), higher pulmonary artery systolic pressure (35 +/- 14 vs 29 +/- 11 mm Hg, p less than 0.04), and lower left ventricular ejection fractions (0.42 +/- 0.13 vs 0.53 +/- 0.14, p less than 0.001). Eight patients (28%) with inducible pulsus alternans had a normal left ventricular ejection fraction (greater than 0.50) and left ventricular end-diastolic pressure (less than 13 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)

Pulsus alternans induced by inferior vena caval occlusion in man

To assess the effect of rapid preload reduction on left ventricular performance in nonischemic cardiomyopathy, 11 patients were studied during inferior vena caval (IVC) balloon occlusion. Five developed sustained pulsus alternans. During pulsus alternans, the strong beats demonstrated systolic performance characteristics similar to baseline values, despite a drop in both left ventricular (LV) end-diastolic diameter (66 +/- 13 to 61 +/- 13 mm; p less than 0.05) and LV end-diastolic pressure (21 +/- 8 to 9 +/- 6 mmHg; p less than 0.05). In contrast, the weak beats demonstrated a reduction in peak systolic pressure (130 +/- 36 to 109 +/- 33 mmHg; p less than 0.02), fractional shortening (20% +/- 4% to 17% +/- 9%; p less than 0.05) and peak positive dP/dt (1,006 +/- 224 to 921 +/- 287 mmHg; p less than 0.05). Measures of diastolic performance (peak negative dP/dt, the time constant of LV relaxation, the length of diastasis, and LV end-diastolic stress) were not different between baseline beats and the strong beats; and only LV end-diastolic stress differed when baseline beats were compared to the weak beats. When the strong beats were compared to the weak beats during induced pulsus alternans, significant differences were observed in peak systolic pressure, peak positive dP/dt, and fractional shortening, but no differences in any measured diastolic parameter was observed. A slight difference was noted in the left ventricular end-diastolic diameters, with the weak beat consistently beginning at a slightly smaller diameter (61 +/- 13; mm vs 59 +/- 13; p less than 0.05). In summary, these data are consistent with an augmentation and deletion of intrinsic contractile forces in association with an alternation in preload on a beat-to-beat basis as best describing left ventricular performance during pulsus alternans.

Model of mechanical alternans in the mammalian myocardium

A model is proposed to elucidate the cause and mechanism of mechanical alternans in cardiac muscle in terms of discrete calcium movements. Mechanical alternans, the cause of which lies within the borders of excitation-contraction-coupling (ECC), is analyzed. In this case, the "input" of the ECC system (the action potentials and intervals) is constant while the "output" (contractile force) oscillates between two constant values, indicating that the system has a "memory" with two "internal states". It is proposed that these two "states" are associated with a part of the sarcoplasmic reticulum ("releasable terminal") containing the readily releasable calcium. A mechanism of "calcium-concentration-dependent threshold" is suggested to govern the "release function", i.e. the release of calcium from the "releasable terminal" to the myofilaments. The "release function" is analyzed in both the linear and the non-linear cases and its implication on the initiation of sustained and transient mechanical alternans are described. The dependence of mechanical alternans on a disturbance is also explained. The model response resembles the experimental observations of mechanical alternans in mammalian myocardium in the following manners: abrupt transition from low to high heart rates, slow progressive acceleration of rate, variations in persistence at subthreshold rates, effect of premature and delayed beat following the small and large beats, restitution curves, and transient mechanical alternans initiated by a delayed beat.

Mitral valve alternans

An echogram showing mitral valve alternans was recorded in a patient with advanced cardiomyopathy and pulsus alternans induced by premature ventricular depolarizations. Decreased left ventricular emptying by the weak beat was followed by blunting of the subsequent mitral valve E point, a finding compatible with a significant elevation of left ventricular pressure in early diastole. Both alternating systolic (contractile state) and diastolic (pressure and dimension) variables seemed to participate in the alternans phenomenon in this patient.

Pulsus alternans: its influence on systolic and diastolic function in aortic valve disease

Left ventricular high fidelity pressure measurements and simultaneous biplane cineangiocardiography were performed in 12 patients with severe aortic valve disease (aortic stenosis in 10, aortic insufficiency in 1 and combined valve lesion in 1). Left ventricular contractility was estimated from maximal rate of left ventricular pressure rise (max dP/dt), peak measured velocity of contractile element shortening (Vpm) and mean circumferential fiber shortening velocity. Left ventricular relaxation was assessed in 12 patients from the time constant (T) of the decline in left ventricular pressure; this constant was calculated from a nonlinear regression analysis of pressure and time (method 1) and a linear regression analysis of pressure and negative dP/dt (method 2). Left ventricular diastolic function was evaluated in nine patients from simultaneous diastolic pressure-volume relations during the strong and weak beats. During pulsus alternans, heart rate and left ventricular end-diastolic pressure remained unchanged, whereas peak systolic pressure (220 versus 204 mm Hg, p less than 0.01) and end-systolic pressure (101 versus 95 mm Hg, p less than 0.01) were significantly higher during the strong beat than during the weak beat. Max dP/dt was alternating (2,162 versus 1,964 mm Hg, p less than 0.05), whereas the peak velocity of contractile element shortening remained unchanged (1.21 versus 1.18 ML/s). Systolic shortening of the left ventricular minor axis was significantly (p less than 0.02) greater during the strong (24%) than during the weak (19%) beat, but that of the left ventricular major axis remained essentially unchanged (8 versus 7%).(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanics of pulsus alternans in aortic valve stenosis

Differences in the mechanics of strong and weak contractions during sustained pulsus alternans were studied in 4 patients with aortic valve stenosis (AS). No significant difference was observed between strong (S) and weak (W) beats in M-mode echographic end-diastolic minor-axis dimension or end-diastolic meridional wall stress. Peak systolic meridional stress (S:225 X 10(3) dynes/cm2; W:205 X 10(3) dynes/cm2), the time integral of left ventricular (LV) meridional systolic stress (S:5,000 X 10(3) dynes/cm2; W:4,500 X 10(3) dynes/cm2) and the area of a stress dimension loop (S:202 X 10(3) dyne/cm; W 165 X 10(3) dyne/cm) were all greater for strong beats. However, end-systolic meridional stress (S:100 X 10(3) dynes/cm2; W:115 X 10(3) dynes/cm2) and end-systolic minor-axis dimension (S:4.75 cm; W:5.0 cm) were significantly greater for weak beats. Stress-length relations, derived from resting and postnitroglycerin determinations, revealed higher end-systolic dimensions for weak beats at any level of limiting afterload, suggesting diminished contractile performance of weak beats. Additionally, fractional minor-axis shortening for weak beats was diminished, at any level of end-systolic stress, in comparison with that for strong beats. The results are supportive of theories suggesting alternating contractile performance during pulsus alternans.