The pathologies that involve the heart are still the main causes of death in European countries, and acute myocardial infarction (AMI) is constantly present in this mortality rate. AMI occurs when there is an interruption of the blood supply to the heart, which is carried out by the coronary arteries.¹

Older people present some alterations, such as decreased functional capacity and physiological reserve, that generate a negative impact on quality of life. Geriatric syndrome, frailty, loss of peripheral muscle strength, decreased vital capacity, decreased walking speed, and increased risk of falling are factors that interfere with the health of older people, making their functionality more limited. Therefore, these post-AMI patients need to be evaluated in an individualized way because they can present a loss of functional capacity and difficulty in performing their activities of daily living (ADL).^2-7

In post-AMI patients, the six-minute walk test (6MWT) can be used to evaluate the individual during exercise in the respiratory, cardiac, and metabolic areas. The 6MWT is a submaximal test of the patient's cardiac capacity, the gold standard for the evaluation and prescription of cardiac rehabilitation.³ However, Pin,⁸ in his study, points out the inability of some individuals to walk for six minutes because of muscle weakness, frailty, poor gait, low resistance acquired during hospitalization, physical disability, or associated pathology.

An alternative to the 6MWT is the 2-minute walk test (TC2M). The walk test causes physiological changes in the patient's cardiorespiratory system, including changes in heart rate (HR), respiratory rate, systemic blood pressure (BP), perceived exertion, oxygen saturation, and other parameters.^9-12

Evaluations made with different populations show that the distance walked during the 2MWT is proportional to the distance walked during the 6MWT. In this sense, it is possible to affirm the feasibility of using the 2MWT, which can be encouraged in specific populations, such as patients with heart diseases, chronic obstructive pulmonary disease, neuromuscular diseases, amputees and elderly individuals unable to undergo the 6MWT. Thus, this is an alternative strategy for the assessment process in services where the time for patient care is more limited.¹³

This research, in turn, is important for the scientific society since there is a lack of evidence on the physiological changes during the two-minute walk test (2MWT). Therefore, this study aims to evaluate the feasibility of the 2MWT in elderly patients after AMI.

The study included 51 patients, 41 of whom were male (80%) and a mean age of 67 ± 8 years. The most prevalent comorbidity was SAH. Table 1 shows the average distance traveled.

Table 1

Variable	Mean ± SD	n (%)
Gender
Male		41 (80%)
Female		10 (20%)
Age (years)	67 ± 8
BMI (kg/m2)	26 ± 3
Comorbidities
SAH		31 (61%)
DM		26 (51%)
DLP		22 (43%)
Alcoholism		6 (12%)
Sedentarism		17 (33%)
LVEF (%)	56 ± 11
Use of beta-blockers		31 (61%)
Length of hospital stay (days)	5 ± 2
NYHA
I		6 (12%)
II		33 (65%)
III		9 (18%)
IV		3 (6%)
Type of AMI
With ST-segment elevation		31 (61%)
No ST-segment elevation		20 (39%)
Walking distance in 2MWT (meters)	157 ± 22

BMI: Body Mass Index; SAH: Systemic Arterial Hypertension; DM: Diabetes Mellitus; DLP: Dyslipidemia; LVEF: Left Ventricular Ejection Fraction; NYHA: New York Heart Association; 2MWT: Two Minutes’ Walk Test.

After the test was completed, cardiovascular behavior was altered within expectations, with no impairment of cardiovascular function. There was no statistical difference between the pre-test and the post-test and recovery. The values are shown in Table 2 and the central figure.

Table 2

Variable	Pre-Test	Post-Test	Recovery	pa	pb	pc
SBP (mmHg)	112 ± 21	131 ± 15	119 ± 22	0.24	0.34	0.64
DBP (mmHg)	77 ± 12	83 ± 14	79 ± 15	0.43	0.68	0.75
HR (bpm)	75 ± 15	89 ± 19	79 ± 15	0.15	0.59	0.56
DP (mmHgxbpm)	8400 ± 315	11659 ± 285	9401 ± 330	0.07	0.31	0.62
Borg	4 ± 1	8 ± 3	4 ± 2	0.63	0.79	0.84
SpO2 (%)	97 ± 1	96 ± 1	97 ± 2	0.56	0.83	0.82

a. Comparison of pre-test to post-test; b. Comparison of pre-test to recovery; c. Comparison between the three moments; SBP: Systolic Blood Pressure; DBP: Diastolic Blood Pressure; HR: Heart Rate; DP: Double Product; SpO₂: Peripheral Oxygen Saturation.

Table 3 shows that few adverse events occurred during the test. Palpitation was the most prevalent event, followed by dizziness.

Table 3

Adverse events	n (%)
Pain in lower limbs	3 (6%)
Palpitation	8 (17%)
Dyspnea	5 (10%)
Dizziness	7 (14%)
Nausea	3 (6%)

Based on our study, the 2MWT was well tolerated by elderly patients after AMI because there was no significant change in physiological variables and a low incidence of adverse events. Studies on cardiovascular behavior during the performance of the 2MWT are still scarce, so we made a parallel with studies that used the 6MWT.

Nogueira et al.¹⁷ and Sancho et al.¹⁸ noticed that all post-AMI patients were able to perform the 6MWT, and in turn, there were no adverse events. No patient needed to take breaks, showing that the test was safe and well tolerated by the patients, as well as Araújo et al.,¹⁹ who did not detect adverse events. These data corroborate our results since all elderly post-AMI were able to complete the 2MWT. Furthermore, few adverse events were observed without any more serious impairment, indicating that it is safe to perform the test in post-AMI elderly patients.

Pedrosa and Holanda²⁰ describe the importance and relevance of the test since there is naturally a decline in motor and cardiovascular functions in older people during the test before and after AMI. The article points to a correlation between the 2MWT and 6MWT as far as aerobic endurance is concerned since reduced and/or decreased mobility directs patients to factors related to functional morbidities, where one can relate the higher energy expenditure due to immobility, consequently, to a cardiovascular decline, which are intrinsically related. It is also worth mentioning that Pedrosa and Holanda²⁰ suggest the 2MWT as an alternative for a quick test when compared to the 6MWT since there is an important correlation between the test results when used to assess the functional capacity of older people.

Diniz et al.²¹ state that the performance of walking tests is safe, even early on, when the behavior of HR, SBP, SpO2 and the subjective perceived exertion are observed. The hemodynamic variations behaved physiologically, increasing during the test and returning to pre-test values after a period of rest.

Physiology explains the cardiovascular changes during the performance of the 2MWT. The HR is controlled by the autonomic nervous system, which in turn triggers electrical signals to the sinoatrial node, triggering its increase. During exercise, HR increases mainly as a result of the decrease in parasympathetic activity to the heart by the mechanoreflex.²²

It is common for post-AMI patients to use beta-blockers because their use is related to improved survival rates. Beta-blockers act by decreasing myocardial oxygen consumption, chronotropic and inotropic action of the heart, reducing HR and the force of contraction of the heart, directly influencing systemic BP. Furthermore, the action of the drugs will inhibit possible disturbances during the test, improving cardiac function and reducing the risk of arrhythmias.^23-26

It is worth mentioning that the effects of the use of beta-blockers in the patients of this group allow the heart to remain stable, avoiding high variations in its behavior during the test, giving more security; this fact may explain our results in the variables HR, SBP and DBP in our study.

The attenuation of the positive effects in the chronotropic phase, given the action of beta-blockers, happens with less evidence during the action of the drug. The data cited above propose a literature review of the pharmacokinetics of these drugs because the evidence does not prove the total interference of beta-blockers in the performance of 2MWT.

It is important to have a tool capable of accurately assessing the patient's functional capacity. The 2MWT proved to be effective in this hospital setting, being easy to apply and safe. Its interpretation serves as a basis for developing a therapeutic plan to minimize the functional impact caused by AMI.

More and more researchers are using the 2MWR and analyzing its results by correlating them with the 6MWT in several populations. Reid et al.²⁷ conducted a study with amputee patients who used prostheses to compare the results between the 6MWT and the 2MWT. With the same purpose, but in patients with neuromuscular diseases Andersen et al.²⁸ investigated whether the 2MWT can be an alternative to the 6MWT to evaluate patients with neuromuscular diseases. Both studies found that the 2MWT is able to predict the outcome and has a high correlation with the 6MWT.

Another relevant point is that there are already equations to predict the test result. Zhang et al.²⁹ evaluated 831 healthy and sedentary individuals with the 2MWT to determine an equation to predict the test result in the Chinese population. With the same objective, Mirza et al.³⁰ conducted their study with 87 Asian adult patients who performed the 2MWT, and Selman et al.¹³ evaluated 390 healthy individuals with the objective of establishing a reference equation to predict the distance walked on the 2MWT. It is noteworthy that none of the studies mentioned the presence of adverse events during the performance of the tests.

Our study has some limitations, such as the lack of a sample size calculation, and the effects of medications used by the patients were not evaluated. Tools capable of measuring the chronotropic and/or inotropic responses with greater prediction, such as Holter, were not used during the tests, as well as the verification of test results, such as echocardiography, ambulatory BP monitoring, or myocardial scintigraphy, to detect possible changes in the patients before and after the test.

We conclude that the 2WMT's performance in the hospital environment presents good feasibility in evaluating submaximal capacity in elderly patients after AMI.