Butt And Hit - The Heart Kidney Saga: A Snap Shot And Long Term Perspectives

Introduction

Tobacco smoking is an universal problem and a malady more so among young adults. Tobacco use in different population groups is reported to have a prevalence of 15% to over 50% among men¹. Large household surveys in recent years have shown that there are about 120 million smokers in India, of whom 37% are all men and 5% are all women in the age group of 30-69 years. Smoking may soon account for 20% of all male deaths and 5% of all female deaths among Indians in the age group of 30-69 1 years

More than 4000 compounds have been identified in the tobacco smoke. This complex mixture of chemical substances has unique pro inflammatory and cyto toxic effects²

Ill effects of smoking (Nicotine) on cardiovascular and renal systems can be attributed to the following mechanisms:

• Smoking (Nicotine) exerts effect on the proximal tubule and renal haemo dynamics resulting in increased GFR, sodium chloride excretion, and urine flow^3,4.

• Smoking(Nicotine) causes marked attenuation of alpha and beta adrenergic blockade, prolonged increase in plasma norepinephrine and epinephrine, thus leading to a marked and prolonged increase in heart rate and blood pressure⁵

• Smoking (Nicotine) accelerates atherosclerotic process by its pro sclerotic and pro thrombotic effects.

• Smoking (Nicotine) has an unfavorable influence on autonomic balance leading to QT prolongation and prolonged QTc with a lowered ventricular threshold and occurrence of sudden cardiac death⁶.

Materials and Methods

The present cross sectional study conducted at the tertiary care medical college hospital at Mangalore, coastal Karnataka comprised of 75 young male smokers in the age group of 20-40 years, who smoked more than 10 cigarettes per day for more than 5 years. Age and sex matched controls were also drawn. Females, hypertensives, diabetics, patients with known renal diseases, patients taking drugs that affect QT interval and patients taking drugs affecting GFR were excluded from the study.

After obtaining written informed consent from each participant a detailed history with particular emphasis on duration and number of cigarettes smoked was sought and a thorough clinical examination was performed. Blood pressure (BP) was recorded from the right arm in sitting posture using mercury sphygmomanometer by a single person (to avoid inter personal variability). An average of two BP readings taken five minutes apart was considered for analysis. Blood sample for creatinine estimation was drawn soon after BP measurement and GFR was calculated using creatinine clearance rate using the cockroftt gault formula. $$\text{Ccr}=\frac{(140-\text{Age})\text{X weight [kg]}}{\mathrm{Cr}?[\mathrm{m}\mathrm{g}/\mathrm{d}\mathrm{l}]�72}$$

Electro cardiograph (ECG) was obtained at the same time and analyzed for any abnormalities in terms of rate, rhythm, axis deviation, chamber hypertrophy, ischaemia, and QT prolongation.

Chi square test was employed for analysis of observations and conclusions were drawn from the same.

Observations and Results

• In the present study, mean age of smokers was 31.27 years while it was the same 31.78 years for the non smoker control group also (Table 1).

• Maximum smokers belonged to the age group of 26-30 years (Table 2).

• Raised systolic BP in the pre hypertension range of 121130 mmHg was noted in the 61.2% of smokers as compared to 38.8% among non smokers.(Table 3, Fig 1). Out of this 65.2% had a smoking history of more than 10 years while 28.8% had less than 10 years of smoking history, thus demonstrating a clear statistically significant (P < 0.0001) correlation between smoking, duration of smoking and raised systolic BP (Table 4, Fig 2) There was no significant correlation with respect to diastolic BP between smokers and non smokers and with respect to duration of smoking.( Table 5, Fig 3 ).

• QTc interval was significantly prolonged in smokers as compared to non smokers, which was statistically significant with P < 0.05. However no correlation was found in relation to the duration of smoking. (Table 6, Fig 4).

• GFR decreased with increased duration of smoking ( > 10 years ) as compared to lesser duration of smoking ( < 10 years ), which was statistically significant with P = 0.042. However there was no statistically significant difference of GFR between smokers and non smokers. (Table 7&8, Fig 5&6).

Discussion

Effect of smoking on cardiovascular and renal system is very vital and forms a long term perspective particularly among young adults. The present study being unique has addressed this issue by involving young adults in the age group of 20-40 years only.

Wang et al⁷ had observed that young smokers were at higher risk of developing cardiovascular risks as compared to older adults. Study by Paola et al⁸ on older men demonstrated a higher systolic BP among smokers as compared to non smokers ( 144 mmhg Vs 140 mmhg ), but with no such differences in diastolic BP among the two groups. However our study conducted on young men also confirms the same, which was statistically significant too (P < 0.05).

Study by Okubo et al⁹ found lesser systolic BP in light to moderate smokers as compared to non smokers (121 mmhg Vs 123 mmhg). However Our study contradicts the above findings as higher percentage of smokers were in the Pre hypertension range (defined as systolic BP of 121-139 mmhg or diastolic BP of 81-89 mmhg by JNC 7) compared to non smokers and systolic hypertension was evident in smokers with prolonged duration of smoking ( > 10 years ) as compared to lesser duration of smoking (<10 years ). The above findings of our study may be attributed to chronic smoking induced atherogenesis in large capacitance vessels which is easily amenable to correction by modifying the risk factor of smoking.

Study by Mehmet illeri et al^6,9 demonstrated smoking predisposes to prolongation of QT interval and QTc dispersion, thus increasing the risk of sudden cardiac death in them due to lowered ventricular fibrillation threshold and pro arrhythmic effect of catecholamine and nor epinephrine spillover. Our present study reconfirms the same and was statistically significant too with P < 0.05.

Halimi et al¹⁰ in his study on the effects of smoking on renal function concluded that creatinine clearance was higher in smokers as compared to non smokers (100.6ml/min Vs 98.8ml/min) and the glomerular hyper filtration was associated with increased intra glomerular pressure and proteinuria. Our present study also confirmed a higher GFR among smokers compared to non smokers but was not statistically significant ( P > 0.05 ).

Conclusions

From the present study we conclude the following:

• Smoking predisposes to pre hypertension, systolic hypertension and prolonged QT interval among young smokers as compared to age, sex matched non smokers, thus increasing their risk to develop overt hypertension and associated cardiovascular complications including sudden cardiac death.

• Prolonged duration of smoking (> 10 years) results in GFR reduction and raised systolic blood pressure, thus increasing the risk of long term cardiovascular complications and also long term deterioration of renal functions among young smokers.

• Young smokers form an important risk group who require to be “COUNCELLED TO QUIT SMOKING” to prevent long term smoking induced cardiovascular and renal risks. THIS GOES A LONG WAY IN ACHIEVING A POLLUTION FREE ENVIRONMENT AND ALSO A PRODUCTIVE, HEALTHY YOUNG POPULATION AND SOCIETY.

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Figure 1.

Higher percentage of young smokers in the pre-hypertension range as compared to age matched non smokers (61.2 % VS 38.8%).

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Figure 3

Diastolic Blood pressure between the two groups comparable but not statistically significant.

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Figure 5.

GFR between smokers and non smokers comparable but not statistically significant.

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Figure 2.

SBP (pre hypertensive range) significantly higher among smokers with smoking duration more than 10 years.

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Figure 4.

QTc in smokers significantly higher than non smokers.

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Figure 6

GFR reduction significantly higher with prolonged duration (>10years) of smoking.

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